The American Journal of Orthopedics

Although the number of total hip arthroplasties (THAs) being performed in the United States is increasing, revision THAs are more common.¹ Many acetabular revisions can be successfully performed with standard or jumbo cementless acetabular cups, but major osseous deficiencies typically require reconstruction with a cage or cup/cage that bridges gaps in the pelvis and obtains fixation of the arthroplasty components.^2,3 Cages and rings have been combined with all-polyethylene acetabular components (ie, all-polyethylene cups, or APCs) to reconstruct pelvic bone defects, but complications, including APC dissociation (Figure 1) and postoperative instability, can occur despite stable fixation of cage to pelvis.⁴ The incidence of dislocations with pelvic reconstruction rings using APCs has been reported to be 11%.⁴ If an APC has to be replaced because of wear, then major surgery may be required to extract the worn cup and cement a new cup in its place.

In this article, we describe a technique in which a metal, multihole acetabular shell is cemented into the cage or ring construct, avoiding some of the complications associated with traditional techniques by permitting use of a variety of liners.

Materials and Methods

We retrospectively reviewed the cases of all of Dr. Bolanos’ patients who underwent acetabular revision THA with cage reconstruction between February 1, 1998 and October 9, 2006. During this period, we were cementing a modular metal shell into the cage instead of an APC or polyethylene liner. All patients who underwent revision THA with cage reconstruction during the study period were included. Bone defects were treated with structural or morselized bone allograft. Every reconstruction involved use of an antiprotrusio cage or ring secured to the pelvis with screws, and a multihole acetabular shell cemented into place with a polyethylene liner applied. Elevated rims, lateralized liners, and constrained liners were used as needed to optimize stability. Femoral components were retained. Cage size was based on matching the osseous deficiencies. Shell size was determined by the inner diameter of the corresponding cage. Liner size was based on matching the shell and femoral head. During this period, none of the patients had other reconstructive techniques, such as trabecular metal augmentation, in combination with a modular acetabular shell, cup/cage reconstruction, or custom triflange components.

Patients engaged in protected weight-bearing ambulation for 3 months after surgery and were then permitted full, unrestricted activity. The primary outcome was mechanical failure of the reconstruction, or reoperation (Table). All reconstructions in this series consisted of acetabular revisions for aseptic loosening.

Surgical Technique

Six consecutive cases of pelvic discontinuity and 7 cases of segmental acetabular bone loss required use of cages or rings. Reconstruction cages were used to secure fixation to the ilium and ischium. With the technique described in this article, we used screws with rounded, prominent heads rather than flat heads between the cup and the cage or ring (Synthes, 6.5 mm) to ensure adequate cement mantle. The rounded screw heads were left prominent to approximate the function of cement pegs found on APCs. Screws were placed into the anterior, superior, medial, and posterior aspects of the cage to ensure adequate cement mantle between cup and cage. This was confirmed with trial placement of the cup into the cage before cementation and observation of the uniformity of the space between cup and cage. Trial placement also confirmed that the screws did not interfere with appropriate positioning of the cup. A multihole, metal acetabular cup was then cemented in the cage or ring such that cement extruded around the shell and into the holes of the cup and the cage, securing the cup to the cage. Use of a multihole, metal shell resulted in excellent cement fixation because the multiple holes created multiple circumferential cement pegs. Various liner options could then be used to optimize stability of the reconstruction. In some cases, excessive cement extruded into the interior aspect of the shell and hardened before curettage. If the excess cement could interfere with complete seating/locking of the liner, then a high-speed burr was used to easily remove cement (Figure 2). Polyethylene liners were then inserted into the shell. Femoral reconstruction was then performed, if needed, and stability of the arthroplasty checked. This technique allows the surgeon to then select from a variety of polyethylene liners as needed to optimize stability. Liners with elevated rims, lateralized liners, and constrained liners could be interchangeable options with this technique.

Results

Thirteen patients with major osseous deficiencies of the pelvis were treated using this technique. At mean follow-up of 64.2 months (range, 3-133 months), 10 of the 13 patients had favorable outcomes without further surgery. One patient developed recurrent aseptic loosening that required re-revision, another patient developed recurrent instability that required acetabular liner and femoral head exchange, and a third patient with poor balance fell multiple times. This patient’s ninth fall resulted in dissociation of the acetabular shell from the cage (Figure 3), treated with placement of another cemented multihole metal shell with a standard liner. As dislocations recurred, the liner was changed to a constrained liner (Figure 4). The patient did not have any further dislocations or other hip-related problems. Integrity of cemented shell-cage fixation was maintained in 12 of the 13 patients at final follow-up.

Discussion

We have described a novel technique that facilitates reconstruction of major osseous deficiencies of the pelvis. The technique involves cementation of a multihole, metal acetabular shell into a cage or ring, permitting use of modular liners. The modularity in this approach to major hip reconstruction provides stability-optimization options that are not available with APCs. So far, the technique has demonstrated more advantages than disadvantages, so the indications for its use would be whenever a cage is used for pelvic reconstruction. Traditional techniques involve cementing an APC into the cage or ring. Use of multihole, metal shells for this purpose has several theoretical advantages. Multiple holes and the textured surface allow more interdigitation of cement with cup than APCs do; this interdigitation may improve the durability of the cemented interface. Cement also extrudes through the holes of the cage to secure the cup to the pelvis, as is done with cementation of APCs. Introduction of trabecular metal shells may also provide an even more secure bond to the shell, compared with APCs, though durability of a cemented trabecular metal interface has not been established. In addition, mechanical alignment guides cannot fasten as securely onto some APCs.

Nonmodular, cemented, metal-backed acetabular components, which were commonly used in hip arthroplasties at one time, were abandoned because of their relatively high loosening rate and because of advantages noted with modular components.⁵ The nonmodular components had been developed because of their theoretical advantages of improved distribution of forces into the cement mantle.^5,6 However, those models had a relatively smooth metallic surface, which probably did not bond as well to cement as the shells used with the technique described in this article.

Dislocations can occur because of inadequately placed cups. Metallic cups can be improperly positioned, as can APCs. An advantage of the technique we have described over APCs is that liners with raised rims can be inserted with the apex placed wherever needed to best address instability. Dislocations can also occur because of factors such as inadequate offset and cognitive impairments. Our technique allows use of offset liners and constrained liners. Although these options may not prevent further dislocations, they often mitigate instability issues. Constrained liners and lateralized liners can be easily placed, and elevated rims can be swiveled as needed for stability. As use of cementless, metal-backed, modular acetabular components is common in primary THAs, most surgeons are familiar with the modular liner options available with use of the technique described in this article.

 In this setting, modular, metal acetabular shells have the advantage of allowing surgeons to use the alignment guides they are accustomed to using. Modularity is another significant advantage over APCs. When an APC wears down, the component must be extracted to permit implantation of a new APC. With metal shells, a worn liner can be exchanged relatively easily. Modularity also gives surgeons many more options for addressing instability. Elevated rims can be moved, head sizes can be changed, and lateralized or constrained liners can be implanted easily. By comparison, with APCs, stability can be addressed only by modifying the femoral component or taking hip precautions which restrict range of motion of the hip. Modification of the femoral component is not possible with nonmodular femoral components in place (Figure 5). A potential disadvantage of this technique is increased cost associated with use of another component.

This small series of patients has had an excellent rate of success with cementation of multihole, metal-backed acetabular components into a cage or ring. These components may offer more secure fixation than APCs to cement extruded into the multiple holes, and improved metallurgy, such as trabecular metal. Surgeons who want to use modular components may prefer this technique because it allows them to select from various liner options. Surgeons should consider this technique for patients who need major pelvic reconstruction, though a larger study with longer follow-up is needed to determine its long-term durability.

Although the novel technique we have described has been helpful in our experience, this study had several limitations—small series, retrospective study, relatively short follow-up, lack of control group and functional data—that may have affected its conclusions. Further study and follow-up are needed to better determine the utility of this technique in clinical practice.

Although the number of total hip arthroplasties (THAs) being performed in the United States is increasing, revision THAs are more common.¹ Many acetabular revisions can be successfully performed with standard or jumbo cementless acetabular cups, but major osseous deficiencies typically require reconstruction with a cage or cup/cage that bridges gaps in the pelvis and obtains fixation of the arthroplasty components.^2,3 Cages and rings have been combined with all-polyethylene acetabular components (ie, all-polyethylene cups, or APCs) to reconstruct pelvic bone defects, but complications, including APC dissociation (Figure 1) and postoperative instability, can occur despite stable fixation of cage to pelvis.⁴ The incidence of dislocations with pelvic reconstruction rings using APCs has been reported to be 11%.⁴ If an APC has to be replaced because of wear, then major surgery may be required to extract the worn cup and cement a new cup in its place.

In this article, we describe a technique in which a metal, multihole acetabular shell is cemented into the cage or ring construct, avoiding some of the complications associated with traditional techniques by permitting use of a variety of liners.

Materials and Methods

We retrospectively reviewed the cases of all of Dr. Bolanos’ patients who underwent acetabular revision THA with cage reconstruction between February 1, 1998 and October 9, 2006. During this period, we were cementing a modular metal shell into the cage instead of an APC or polyethylene liner. All patients who underwent revision THA with cage reconstruction during the study period were included. Bone defects were treated with structural or morselized bone allograft. Every reconstruction involved use of an antiprotrusio cage or ring secured to the pelvis with screws, and a multihole acetabular shell cemented into place with a polyethylene liner applied. Elevated rims, lateralized liners, and constrained liners were used as needed to optimize stability. Femoral components were retained. Cage size was based on matching the osseous deficiencies. Shell size was determined by the inner diameter of the corresponding cage. Liner size was based on matching the shell and femoral head. During this period, none of the patients had other reconstructive techniques, such as trabecular metal augmentation, in combination with a modular acetabular shell, cup/cage reconstruction, or custom triflange components.

Patients engaged in protected weight-bearing ambulation for 3 months after surgery and were then permitted full, unrestricted activity. The primary outcome was mechanical failure of the reconstruction, or reoperation (Table). All reconstructions in this series consisted of acetabular revisions for aseptic loosening.

Surgical Technique

Six consecutive cases of pelvic discontinuity and 7 cases of segmental acetabular bone loss required use of cages or rings. Reconstruction cages were used to secure fixation to the ilium and ischium. With the technique described in this article, we used screws with rounded, prominent heads rather than flat heads between the cup and the cage or ring (Synthes, 6.5 mm) to ensure adequate cement mantle. The rounded screw heads were left prominent to approximate the function of cement pegs found on APCs. Screws were placed into the anterior, superior, medial, and posterior aspects of the cage to ensure adequate cement mantle between cup and cage. This was confirmed with trial placement of the cup into the cage before cementation and observation of the uniformity of the space between cup and cage. Trial placement also confirmed that the screws did not interfere with appropriate positioning of the cup. A multihole, metal acetabular cup was then cemented in the cage or ring such that cement extruded around the shell and into the holes of the cup and the cage, securing the cup to the cage. Use of a multihole, metal shell resulted in excellent cement fixation because the multiple holes created multiple circumferential cement pegs. Various liner options could then be used to optimize stability of the reconstruction. In some cases, excessive cement extruded into the interior aspect of the shell and hardened before curettage. If the excess cement could interfere with complete seating/locking of the liner, then a high-speed burr was used to easily remove cement (Figure 2). Polyethylene liners were then inserted into the shell. Femoral reconstruction was then performed, if needed, and stability of the arthroplasty checked. This technique allows the surgeon to then select from a variety of polyethylene liners as needed to optimize stability. Liners with elevated rims, lateralized liners, and constrained liners could be interchangeable options with this technique.

Results

Thirteen patients with major osseous deficiencies of the pelvis were treated using this technique. At mean follow-up of 64.2 months (range, 3-133 months), 10 of the 13 patients had favorable outcomes without further surgery. One patient developed recurrent aseptic loosening that required re-revision, another patient developed recurrent instability that required acetabular liner and femoral head exchange, and a third patient with poor balance fell multiple times. This patient’s ninth fall resulted in dissociation of the acetabular shell from the cage (Figure 3), treated with placement of another cemented multihole metal shell with a standard liner. As dislocations recurred, the liner was changed to a constrained liner (Figure 4). The patient did not have any further dislocations or other hip-related problems. Integrity of cemented shell-cage fixation was maintained in 12 of the 13 patients at final follow-up.

Discussion

We have described a novel technique that facilitates reconstruction of major osseous deficiencies of the pelvis. The technique involves cementation of a multihole, metal acetabular shell into a cage or ring, permitting use of modular liners. The modularity in this approach to major hip reconstruction provides stability-optimization options that are not available with APCs. So far, the technique has demonstrated more advantages than disadvantages, so the indications for its use would be whenever a cage is used for pelvic reconstruction. Traditional techniques involve cementing an APC into the cage or ring. Use of multihole, metal shells for this purpose has several theoretical advantages. Multiple holes and the textured surface allow more interdigitation of cement with cup than APCs do; this interdigitation may improve the durability of the cemented interface. Cement also extrudes through the holes of the cage to secure the cup to the pelvis, as is done with cementation of APCs. Introduction of trabecular metal shells may also provide an even more secure bond to the shell, compared with APCs, though durability of a cemented trabecular metal interface has not been established. In addition, mechanical alignment guides cannot fasten as securely onto some APCs.

Nonmodular, cemented, metal-backed acetabular components, which were commonly used in hip arthroplasties at one time, were abandoned because of their relatively high loosening rate and because of advantages noted with modular components.⁵ The nonmodular components had been developed because of their theoretical advantages of improved distribution of forces into the cement mantle.^5,6 However, those models had a relatively smooth metallic surface, which probably did not bond as well to cement as the shells used with the technique described in this article.

Dislocations can occur because of inadequately placed cups. Metallic cups can be improperly positioned, as can APCs. An advantage of the technique we have described over APCs is that liners with raised rims can be inserted with the apex placed wherever needed to best address instability. Dislocations can also occur because of factors such as inadequate offset and cognitive impairments. Our technique allows use of offset liners and constrained liners. Although these options may not prevent further dislocations, they often mitigate instability issues. Constrained liners and lateralized liners can be easily placed, and elevated rims can be swiveled as needed for stability. As use of cementless, metal-backed, modular acetabular components is common in primary THAs, most surgeons are familiar with the modular liner options available with use of the technique described in this article.

 In this setting, modular, metal acetabular shells have the advantage of allowing surgeons to use the alignment guides they are accustomed to using. Modularity is another significant advantage over APCs. When an APC wears down, the component must be extracted to permit implantation of a new APC. With metal shells, a worn liner can be exchanged relatively easily. Modularity also gives surgeons many more options for addressing instability. Elevated rims can be moved, head sizes can be changed, and lateralized or constrained liners can be implanted easily. By comparison, with APCs, stability can be addressed only by modifying the femoral component or taking hip precautions which restrict range of motion of the hip. Modification of the femoral component is not possible with nonmodular femoral components in place (Figure 5). A potential disadvantage of this technique is increased cost associated with use of another component.

This small series of patients has had an excellent rate of success with cementation of multihole, metal-backed acetabular components into a cage or ring. These components may offer more secure fixation than APCs to cement extruded into the multiple holes, and improved metallurgy, such as trabecular metal. Surgeons who want to use modular components may prefer this technique because it allows them to select from various liner options. Surgeons should consider this technique for patients who need major pelvic reconstruction, though a larger study with longer follow-up is needed to determine its long-term durability.

Although the novel technique we have described has been helpful in our experience, this study had several limitations—small series, retrospective study, relatively short follow-up, lack of control group and functional data—that may have affected its conclusions. Further study and follow-up are needed to better determine the utility of this technique in clinical practice.

Although the number of total hip arthroplasties (THAs) being performed in the United States is increasing, revision THAs are more common.¹ Many acetabular revisions can be successfully performed with standard or jumbo cementless acetabular cups, but major osseous deficiencies typically require reconstruction with a cage or cup/cage that bridges gaps in the pelvis and obtains fixation of the arthroplasty components.^2,3 Cages and rings have been combined with all-polyethylene acetabular components (ie, all-polyethylene cups, or APCs) to reconstruct pelvic bone defects, but complications, including APC dissociation (Figure 1) and postoperative instability, can occur despite stable fixation of cage to pelvis.⁴ The incidence of dislocations with pelvic reconstruction rings using APCs has been reported to be 11%.⁴ If an APC has to be replaced because of wear, then major surgery may be required to extract the worn cup and cement a new cup in its place.

In this article, we describe a technique in which a metal, multihole acetabular shell is cemented into the cage or ring construct, avoiding some of the complications associated with traditional techniques by permitting use of a variety of liners.

Materials and Methods

We retrospectively reviewed the cases of all of Dr. Bolanos’ patients who underwent acetabular revision THA with cage reconstruction between February 1, 1998 and October 9, 2006. During this period, we were cementing a modular metal shell into the cage instead of an APC or polyethylene liner. All patients who underwent revision THA with cage reconstruction during the study period were included. Bone defects were treated with structural or morselized bone allograft. Every reconstruction involved use of an antiprotrusio cage or ring secured to the pelvis with screws, and a multihole acetabular shell cemented into place with a polyethylene liner applied. Elevated rims, lateralized liners, and constrained liners were used as needed to optimize stability. Femoral components were retained. Cage size was based on matching the osseous deficiencies. Shell size was determined by the inner diameter of the corresponding cage. Liner size was based on matching the shell and femoral head. During this period, none of the patients had other reconstructive techniques, such as trabecular metal augmentation, in combination with a modular acetabular shell, cup/cage reconstruction, or custom triflange components.

Patients engaged in protected weight-bearing ambulation for 3 months after surgery and were then permitted full, unrestricted activity. The primary outcome was mechanical failure of the reconstruction, or reoperation (Table). All reconstructions in this series consisted of acetabular revisions for aseptic loosening.

Surgical Technique

Six consecutive cases of pelvic discontinuity and 7 cases of segmental acetabular bone loss required use of cages or rings. Reconstruction cages were used to secure fixation to the ilium and ischium. With the technique described in this article, we used screws with rounded, prominent heads rather than flat heads between the cup and the cage or ring (Synthes, 6.5 mm) to ensure adequate cement mantle. The rounded screw heads were left prominent to approximate the function of cement pegs found on APCs. Screws were placed into the anterior, superior, medial, and posterior aspects of the cage to ensure adequate cement mantle between cup and cage. This was confirmed with trial placement of the cup into the cage before cementation and observation of the uniformity of the space between cup and cage. Trial placement also confirmed that the screws did not interfere with appropriate positioning of the cup. A multihole, metal acetabular cup was then cemented in the cage or ring such that cement extruded around the shell and into the holes of the cup and the cage, securing the cup to the cage. Use of a multihole, metal shell resulted in excellent cement fixation because the multiple holes created multiple circumferential cement pegs. Various liner options could then be used to optimize stability of the reconstruction. In some cases, excessive cement extruded into the interior aspect of the shell and hardened before curettage. If the excess cement could interfere with complete seating/locking of the liner, then a high-speed burr was used to easily remove cement (Figure 2). Polyethylene liners were then inserted into the shell. Femoral reconstruction was then performed, if needed, and stability of the arthroplasty checked. This technique allows the surgeon to then select from a variety of polyethylene liners as needed to optimize stability. Liners with elevated rims, lateralized liners, and constrained liners could be interchangeable options with this technique.

Results

Thirteen patients with major osseous deficiencies of the pelvis were treated using this technique. At mean follow-up of 64.2 months (range, 3-133 months), 10 of the 13 patients had favorable outcomes without further surgery. One patient developed recurrent aseptic loosening that required re-revision, another patient developed recurrent instability that required acetabular liner and femoral head exchange, and a third patient with poor balance fell multiple times. This patient’s ninth fall resulted in dissociation of the acetabular shell from the cage (Figure 3), treated with placement of another cemented multihole metal shell with a standard liner. As dislocations recurred, the liner was changed to a constrained liner (Figure 4). The patient did not have any further dislocations or other hip-related problems. Integrity of cemented shell-cage fixation was maintained in 12 of the 13 patients at final follow-up.

Discussion

We have described a novel technique that facilitates reconstruction of major osseous deficiencies of the pelvis. The technique involves cementation of a multihole, metal acetabular shell into a cage or ring, permitting use of modular liners. The modularity in this approach to major hip reconstruction provides stability-optimization options that are not available with APCs. So far, the technique has demonstrated more advantages than disadvantages, so the indications for its use would be whenever a cage is used for pelvic reconstruction. Traditional techniques involve cementing an APC into the cage or ring. Use of multihole, metal shells for this purpose has several theoretical advantages. Multiple holes and the textured surface allow more interdigitation of cement with cup than APCs do; this interdigitation may improve the durability of the cemented interface. Cement also extrudes through the holes of the cage to secure the cup to the pelvis, as is done with cementation of APCs. Introduction of trabecular metal shells may also provide an even more secure bond to the shell, compared with APCs, though durability of a cemented trabecular metal interface has not been established. In addition, mechanical alignment guides cannot fasten as securely onto some APCs.

Nonmodular, cemented, metal-backed acetabular components, which were commonly used in hip arthroplasties at one time, were abandoned because of their relatively high loosening rate and because of advantages noted with modular components.⁵ The nonmodular components had been developed because of their theoretical advantages of improved distribution of forces into the cement mantle.^5,6 However, those models had a relatively smooth metallic surface, which probably did not bond as well to cement as the shells used with the technique described in this article.

Dislocations can occur because of inadequately placed cups. Metallic cups can be improperly positioned, as can APCs. An advantage of the technique we have described over APCs is that liners with raised rims can be inserted with the apex placed wherever needed to best address instability. Dislocations can also occur because of factors such as inadequate offset and cognitive impairments. Our technique allows use of offset liners and constrained liners. Although these options may not prevent further dislocations, they often mitigate instability issues. Constrained liners and lateralized liners can be easily placed, and elevated rims can be swiveled as needed for stability. As use of cementless, metal-backed, modular acetabular components is common in primary THAs, most surgeons are familiar with the modular liner options available with use of the technique described in this article.

 In this setting, modular, metal acetabular shells have the advantage of allowing surgeons to use the alignment guides they are accustomed to using. Modularity is another significant advantage over APCs. When an APC wears down, the component must be extracted to permit implantation of a new APC. With metal shells, a worn liner can be exchanged relatively easily. Modularity also gives surgeons many more options for addressing instability. Elevated rims can be moved, head sizes can be changed, and lateralized or constrained liners can be implanted easily. By comparison, with APCs, stability can be addressed only by modifying the femoral component or taking hip precautions which restrict range of motion of the hip. Modification of the femoral component is not possible with nonmodular femoral components in place (Figure 5). A potential disadvantage of this technique is increased cost associated with use of another component.

This small series of patients has had an excellent rate of success with cementation of multihole, metal-backed acetabular components into a cage or ring. These components may offer more secure fixation than APCs to cement extruded into the multiple holes, and improved metallurgy, such as trabecular metal. Surgeons who want to use modular components may prefer this technique because it allows them to select from various liner options. Surgeons should consider this technique for patients who need major pelvic reconstruction, though a larger study with longer follow-up is needed to determine its long-term durability.

Although the novel technique we have described has been helpful in our experience, this study had several limitations—small series, retrospective study, relatively short follow-up, lack of control group and functional data—that may have affected its conclusions. Further study and follow-up are needed to better determine the utility of this technique in clinical practice.

High tibial osteotomy has proved successful in treating unicompartmental arthritis in young, active patients.^1-3 However, this procedure fails over time because the other compartments deteriorate.⁴ The next step is conversion of the osteotomy to total knee arthroplasty (TKA). Conversion results vary, with several authors reporting poor outcomes^5-9 and others reporting outcomes equal to those of primary TKA.^10-14

The long-term success of TKA depends on proper restoration of the mechanical axis and soft-tissue balancing.¹⁵ Preexisting extra-articular deformity may adversely affect outcomes. A deformity of more than 15° may make it difficult to obtain intra-articular correction of an extra-articular deformity through soft-tissue balancing alone.¹⁶

In this article, we report the unique case of a patient whose bilateral high tibial osteotomies failed because of excessive extra-articular deformity. TKAs were performed consecutively, in 2 separate settings. Each TKA was combined with a recorrection tibial osteotomy in a single operation, allowing for re-creation of normal knee alignment with ligament balance. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 58-year-old man (weight, 250 pounds; body mass index, 30) underwent staged bilateral medial opening wedge osteotomies using distraction osteogenesis. A uniplanar external fixator was used for fixation on each knee. Before surgery, anatomical axis was 2° (right knee) and –1° (left knee) (Figure 1A), and tibial slope was 9° (right) and 8° (left) (Figures 1B, 1C). The procedures were performed 10 months apart. After surgery, anatomical alignment was 17° valgus (right knee) and 12° valgus (left knee) (Figure 2), and tibial slope was 20° (right) and 13° (left).

The patient received mild relief of his arthritis symptoms. Fifty-six months after the index operation, he decided to undergo conversion of the right high tibial osteotomy to TKA because of progressive painful arthritis of the knee. Excessive valgus alignment caused by the initial osteotomy raised concerns about being able to correct the extra-articular deformity intra-articularly while maintaining kinematic ligament balance. For this reason, a recorrection osteotomy was performed concurrently with the TKA. A posterior cruciate ligament–retaining (PCL-retaining) knee design (NexGen, Zimmer) was selected.

The procedure began with bone cuts for the TKA. Initial cuts were made on the femur. The tibial cut was made in valgus corresponding to the preoperative valgus deformity. The tibial recorrection osteotomy was made at the level of the original osteotomy site. A stemmed tibial component was used to cross the osteotomy site, correcting the valgus deformity and providing stability at the osteotomy site. A 3.5-mm locking compression T-plate (Synthes) was medially placed to prevent loss of correction and control rotation of the osteotomy during healing. The patient began range of motion on postoperative day 1. Continuous passive motion was not used. Protective weight-bearing continued for 6 weeks. After 6 weeks, and once there was radiograph evidence of healing at the osteotomy site, full weight-bearing was allowed.

After 4 months, the patient decided to undergo a similar procedure on the left knee. Postoperative rehabilitation was the same. A year after the bilateral TKAs, the patient maintained a Knee Society Score of 95 and a functional score of 90. After surgery, anatomical alignment was 6° (right knee) and 3° (left knee) (Figure 3), and tibial slope was 6° (right) and 7° (left) (Figures 4A, 4B). In each knee, the PCL was preserved with ligament balance.

Discussion

Clinical outcomes of TKA after high tibial osteotomy vary. Windsor and colleagues⁹ reported that knee arthroplasties after tibial osteotomy were less successful than primary TKAs. In small studies, both Staeheli and colleagues¹⁷ and Katz and colleagues⁵ found that TKA outcomes after osteotomy were satisfactory compared with outcomes of primary TKA without previous osteotomy. A meta-analysis by Ramappa and colleagues¹⁸ showed no difference in outcomes between TKAs with and without previous osteotomy. In addition, there were no differences in outcomes between TKAs performed after opening wedge versus closing wedge osteotomies.¹⁹

An arthritic knee compartment is unloaded when a high tibial osteotomy produces an extra-articular deformity. Neyret and colleagues⁷ reported difficulties in correcting angulations of 9° or more through soft-tissue release. Cameron and Welsh¹⁶ suggested pre–knee arthroplasty correction of the extra-articular deformity for malalignments of more than 15°. In cases of severe malalignment produced by an osteotomy, Katz and colleagues⁵ also suggested that a second osteotomy be performed to correct alignment before TKA.

For TKA after high tibial osteotomy, a neutral plateau resection removes more bone medially than laterally, creating medial laxity. Without correction of the tibial deformity, lateral release (or, as Krackow and Holtgrewe²⁰ advocated, medial advancement) is required for ligament stability. Both technically demanding options may not provide complete stability throughout the arc of motion. In addition, neither corrects for rotational or sagittal deformities (the concern with correcting an extra-articular deformity with intra-articular ligament balancing).

Another option is valgus tibial resection, which maintains native ligament balance at the cost of excessive valgus alignment. In the low-demand patient, a condylar constrained implant provides a means of correcting the malalignment with knee stability.^8,13,17 The increased restraint produces greater forces at the implant–bone interface and may risk early loosening.

The case presented here represents a unique situation of failed bilateral high tibial osteotomies with excessive valgus malalignment. In a similar situation, Papagelopoulos and colleagues²¹ suggested correcting fracture deformities before or at time of knee arthroplasty. Yoshina and colleagues²² reported using a stemmed tibial component with TKA in treating nonunion of a high tibial osteotomy. As mentioned, Katz and colleagues⁵ and Neyret and colleagues⁷ suggested preoperative correction of the osteotomy in cases of severe malalignment. Others have suggested combining recorrection osteotomy and knee arthroplasty in either consecutive operations or a single operation.^23-26 Wolff and colleagues²⁷ and Uchinou and colleagues²⁸ described recorrection osteotomy performed concurrent with TKA. The present article is the first to report a case involving concurrent bilateral recorrection osteotomy and TKA.

In one setting, the recorrection osteotomy is performed after the bony cuts are made for the TKA. The initial tibial plateau resection is performed in valgus at the same degree of malalignment as the osteotomy. This allows the plane of the tibial resection to parallel the floor once the recorrection is finished. With use of a tibial stem crossing the osteotomy site and a derotation plate, adequate fixation of the osteotomy is obtained. The recorrection osteotomy prevents the ligaments from overlengthening, allows the native ligament balance of the knee, and preserves the PCL—which lets the surgeon obtain ligament balance for the TKA throughout the arc of motion, avoiding midstance instabilities and achieving knee alignment rotationally and in the coronal and sagittal planes.

The TKA used in the present case was a PCL-retaining design. Both posterior-stabilized and PCL-retaining designs are reasonable options for use in combination with recorrection osteotomy. A stemmed tibial component is needed to cross the osteotomy site. In our patient’s case, use of a PCL-retaining design was based on surgeon preference and experience.

Patella infera has been noted as a problem in studies on converting high tibial osteotomy to TKA.^9,12,29 A postulated cause is scarring of the infrapatellar tendon after high tibial osteotomy. In addition, a higher incidence of lateral retinacular release has been identified.^9-11 Patella infera did not occur in either knee in the present case, and lateral release was not required.

Our patient’s lateral radiographs (Figures 4A, 4B) showed persistence of the osteotomy plane anterior to the tibia. The osteotomy healed posteriorly but not completely anteriorly. This raises the issue of risk for nonunion when recorrection osteotomy is performed with TKA. Use of a stemmed tibial implant with a derotation plate provides the benefit of intramedullary fixation for the recorrection osteotomy. If the recorrection osteotomy were performed in a separate setting before TKA, plate fixation would be the primary fixation option. Should nonunion occur at the recorrection osteotomy site, revision of the tibial plateau with a new stemmed implant would be required in combination with plate fixation. Madelaine and colleagues³⁰ reported on a series of 15 severe varus knees treated with both osteotomy and TKA. Two nonunions occurred. Fixation was a staple in one case and a cement wedge in the other. Risk for nonunion may be reduced with the combination of stemmed tibial implant and internal fixation with a derotation plate. Protective weight-bearing is recommended for the first 6 postoperative weeks.

Conclusion

Ligament imbalances produced by high tibial osteotomy and exacerbated by conversion to TKA are difficult to address. In this report, we have described successful single-stage high tibial osteotomy recorrection and TKA performed bilaterally in separate settings. With use of a stemmed tibial component and a derotation plate, solid fixation was obtained with an excellent clinical outcome. The malalignment was corrected while ligament balance was maintained for a PCL-retaining TKA design.

High tibial osteotomy has proved successful in treating unicompartmental arthritis in young, active patients.^1-3 However, this procedure fails over time because the other compartments deteriorate.⁴ The next step is conversion of the osteotomy to total knee arthroplasty (TKA). Conversion results vary, with several authors reporting poor outcomes^5-9 and others reporting outcomes equal to those of primary TKA.^10-14

The long-term success of TKA depends on proper restoration of the mechanical axis and soft-tissue balancing.¹⁵ Preexisting extra-articular deformity may adversely affect outcomes. A deformity of more than 15° may make it difficult to obtain intra-articular correction of an extra-articular deformity through soft-tissue balancing alone.¹⁶

In this article, we report the unique case of a patient whose bilateral high tibial osteotomies failed because of excessive extra-articular deformity. TKAs were performed consecutively, in 2 separate settings. Each TKA was combined with a recorrection tibial osteotomy in a single operation, allowing for re-creation of normal knee alignment with ligament balance. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 58-year-old man (weight, 250 pounds; body mass index, 30) underwent staged bilateral medial opening wedge osteotomies using distraction osteogenesis. A uniplanar external fixator was used for fixation on each knee. Before surgery, anatomical axis was 2° (right knee) and –1° (left knee) (Figure 1A), and tibial slope was 9° (right) and 8° (left) (Figures 1B, 1C). The procedures were performed 10 months apart. After surgery, anatomical alignment was 17° valgus (right knee) and 12° valgus (left knee) (Figure 2), and tibial slope was 20° (right) and 13° (left).

The patient received mild relief of his arthritis symptoms. Fifty-six months after the index operation, he decided to undergo conversion of the right high tibial osteotomy to TKA because of progressive painful arthritis of the knee. Excessive valgus alignment caused by the initial osteotomy raised concerns about being able to correct the extra-articular deformity intra-articularly while maintaining kinematic ligament balance. For this reason, a recorrection osteotomy was performed concurrently with the TKA. A posterior cruciate ligament–retaining (PCL-retaining) knee design (NexGen, Zimmer) was selected.

The procedure began with bone cuts for the TKA. Initial cuts were made on the femur. The tibial cut was made in valgus corresponding to the preoperative valgus deformity. The tibial recorrection osteotomy was made at the level of the original osteotomy site. A stemmed tibial component was used to cross the osteotomy site, correcting the valgus deformity and providing stability at the osteotomy site. A 3.5-mm locking compression T-plate (Synthes) was medially placed to prevent loss of correction and control rotation of the osteotomy during healing. The patient began range of motion on postoperative day 1. Continuous passive motion was not used. Protective weight-bearing continued for 6 weeks. After 6 weeks, and once there was radiograph evidence of healing at the osteotomy site, full weight-bearing was allowed.

After 4 months, the patient decided to undergo a similar procedure on the left knee. Postoperative rehabilitation was the same. A year after the bilateral TKAs, the patient maintained a Knee Society Score of 95 and a functional score of 90. After surgery, anatomical alignment was 6° (right knee) and 3° (left knee) (Figure 3), and tibial slope was 6° (right) and 7° (left) (Figures 4A, 4B). In each knee, the PCL was preserved with ligament balance.

Discussion

Clinical outcomes of TKA after high tibial osteotomy vary. Windsor and colleagues⁹ reported that knee arthroplasties after tibial osteotomy were less successful than primary TKAs. In small studies, both Staeheli and colleagues¹⁷ and Katz and colleagues⁵ found that TKA outcomes after osteotomy were satisfactory compared with outcomes of primary TKA without previous osteotomy. A meta-analysis by Ramappa and colleagues¹⁸ showed no difference in outcomes between TKAs with and without previous osteotomy. In addition, there were no differences in outcomes between TKAs performed after opening wedge versus closing wedge osteotomies.¹⁹

An arthritic knee compartment is unloaded when a high tibial osteotomy produces an extra-articular deformity. Neyret and colleagues⁷ reported difficulties in correcting angulations of 9° or more through soft-tissue release. Cameron and Welsh¹⁶ suggested pre–knee arthroplasty correction of the extra-articular deformity for malalignments of more than 15°. In cases of severe malalignment produced by an osteotomy, Katz and colleagues⁵ also suggested that a second osteotomy be performed to correct alignment before TKA.

For TKA after high tibial osteotomy, a neutral plateau resection removes more bone medially than laterally, creating medial laxity. Without correction of the tibial deformity, lateral release (or, as Krackow and Holtgrewe²⁰ advocated, medial advancement) is required for ligament stability. Both technically demanding options may not provide complete stability throughout the arc of motion. In addition, neither corrects for rotational or sagittal deformities (the concern with correcting an extra-articular deformity with intra-articular ligament balancing).

Another option is valgus tibial resection, which maintains native ligament balance at the cost of excessive valgus alignment. In the low-demand patient, a condylar constrained implant provides a means of correcting the malalignment with knee stability.^8,13,17 The increased restraint produces greater forces at the implant–bone interface and may risk early loosening.

The case presented here represents a unique situation of failed bilateral high tibial osteotomies with excessive valgus malalignment. In a similar situation, Papagelopoulos and colleagues²¹ suggested correcting fracture deformities before or at time of knee arthroplasty. Yoshina and colleagues²² reported using a stemmed tibial component with TKA in treating nonunion of a high tibial osteotomy. As mentioned, Katz and colleagues⁵ and Neyret and colleagues⁷ suggested preoperative correction of the osteotomy in cases of severe malalignment. Others have suggested combining recorrection osteotomy and knee arthroplasty in either consecutive operations or a single operation.^23-26 Wolff and colleagues²⁷ and Uchinou and colleagues²⁸ described recorrection osteotomy performed concurrent with TKA. The present article is the first to report a case involving concurrent bilateral recorrection osteotomy and TKA.

In one setting, the recorrection osteotomy is performed after the bony cuts are made for the TKA. The initial tibial plateau resection is performed in valgus at the same degree of malalignment as the osteotomy. This allows the plane of the tibial resection to parallel the floor once the recorrection is finished. With use of a tibial stem crossing the osteotomy site and a derotation plate, adequate fixation of the osteotomy is obtained. The recorrection osteotomy prevents the ligaments from overlengthening, allows the native ligament balance of the knee, and preserves the PCL—which lets the surgeon obtain ligament balance for the TKA throughout the arc of motion, avoiding midstance instabilities and achieving knee alignment rotationally and in the coronal and sagittal planes.

The TKA used in the present case was a PCL-retaining design. Both posterior-stabilized and PCL-retaining designs are reasonable options for use in combination with recorrection osteotomy. A stemmed tibial component is needed to cross the osteotomy site. In our patient’s case, use of a PCL-retaining design was based on surgeon preference and experience.

Patella infera has been noted as a problem in studies on converting high tibial osteotomy to TKA.^9,12,29 A postulated cause is scarring of the infrapatellar tendon after high tibial osteotomy. In addition, a higher incidence of lateral retinacular release has been identified.^9-11 Patella infera did not occur in either knee in the present case, and lateral release was not required.

Our patient’s lateral radiographs (Figures 4A, 4B) showed persistence of the osteotomy plane anterior to the tibia. The osteotomy healed posteriorly but not completely anteriorly. This raises the issue of risk for nonunion when recorrection osteotomy is performed with TKA. Use of a stemmed tibial implant with a derotation plate provides the benefit of intramedullary fixation for the recorrection osteotomy. If the recorrection osteotomy were performed in a separate setting before TKA, plate fixation would be the primary fixation option. Should nonunion occur at the recorrection osteotomy site, revision of the tibial plateau with a new stemmed implant would be required in combination with plate fixation. Madelaine and colleagues³⁰ reported on a series of 15 severe varus knees treated with both osteotomy and TKA. Two nonunions occurred. Fixation was a staple in one case and a cement wedge in the other. Risk for nonunion may be reduced with the combination of stemmed tibial implant and internal fixation with a derotation plate. Protective weight-bearing is recommended for the first 6 postoperative weeks.

Conclusion

Ligament imbalances produced by high tibial osteotomy and exacerbated by conversion to TKA are difficult to address. In this report, we have described successful single-stage high tibial osteotomy recorrection and TKA performed bilaterally in separate settings. With use of a stemmed tibial component and a derotation plate, solid fixation was obtained with an excellent clinical outcome. The malalignment was corrected while ligament balance was maintained for a PCL-retaining TKA design.

High tibial osteotomy has proved successful in treating unicompartmental arthritis in young, active patients.^1-3 However, this procedure fails over time because the other compartments deteriorate.⁴ The next step is conversion of the osteotomy to total knee arthroplasty (TKA). Conversion results vary, with several authors reporting poor outcomes^5-9 and others reporting outcomes equal to those of primary TKA.^10-14

The long-term success of TKA depends on proper restoration of the mechanical axis and soft-tissue balancing.¹⁵ Preexisting extra-articular deformity may adversely affect outcomes. A deformity of more than 15° may make it difficult to obtain intra-articular correction of an extra-articular deformity through soft-tissue balancing alone.¹⁶

In this article, we report the unique case of a patient whose bilateral high tibial osteotomies failed because of excessive extra-articular deformity. TKAs were performed consecutively, in 2 separate settings. Each TKA was combined with a recorrection tibial osteotomy in a single operation, allowing for re-creation of normal knee alignment with ligament balance. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 58-year-old man (weight, 250 pounds; body mass index, 30) underwent staged bilateral medial opening wedge osteotomies using distraction osteogenesis. A uniplanar external fixator was used for fixation on each knee. Before surgery, anatomical axis was 2° (right knee) and –1° (left knee) (Figure 1A), and tibial slope was 9° (right) and 8° (left) (Figures 1B, 1C). The procedures were performed 10 months apart. After surgery, anatomical alignment was 17° valgus (right knee) and 12° valgus (left knee) (Figure 2), and tibial slope was 20° (right) and 13° (left).

The patient received mild relief of his arthritis symptoms. Fifty-six months after the index operation, he decided to undergo conversion of the right high tibial osteotomy to TKA because of progressive painful arthritis of the knee. Excessive valgus alignment caused by the initial osteotomy raised concerns about being able to correct the extra-articular deformity intra-articularly while maintaining kinematic ligament balance. For this reason, a recorrection osteotomy was performed concurrently with the TKA. A posterior cruciate ligament–retaining (PCL-retaining) knee design (NexGen, Zimmer) was selected.

The procedure began with bone cuts for the TKA. Initial cuts were made on the femur. The tibial cut was made in valgus corresponding to the preoperative valgus deformity. The tibial recorrection osteotomy was made at the level of the original osteotomy site. A stemmed tibial component was used to cross the osteotomy site, correcting the valgus deformity and providing stability at the osteotomy site. A 3.5-mm locking compression T-plate (Synthes) was medially placed to prevent loss of correction and control rotation of the osteotomy during healing. The patient began range of motion on postoperative day 1. Continuous passive motion was not used. Protective weight-bearing continued for 6 weeks. After 6 weeks, and once there was radiograph evidence of healing at the osteotomy site, full weight-bearing was allowed.

After 4 months, the patient decided to undergo a similar procedure on the left knee. Postoperative rehabilitation was the same. A year after the bilateral TKAs, the patient maintained a Knee Society Score of 95 and a functional score of 90. After surgery, anatomical alignment was 6° (right knee) and 3° (left knee) (Figure 3), and tibial slope was 6° (right) and 7° (left) (Figures 4A, 4B). In each knee, the PCL was preserved with ligament balance.

Discussion

Clinical outcomes of TKA after high tibial osteotomy vary. Windsor and colleagues⁹ reported that knee arthroplasties after tibial osteotomy were less successful than primary TKAs. In small studies, both Staeheli and colleagues¹⁷ and Katz and colleagues⁵ found that TKA outcomes after osteotomy were satisfactory compared with outcomes of primary TKA without previous osteotomy. A meta-analysis by Ramappa and colleagues¹⁸ showed no difference in outcomes between TKAs with and without previous osteotomy. In addition, there were no differences in outcomes between TKAs performed after opening wedge versus closing wedge osteotomies.¹⁹

An arthritic knee compartment is unloaded when a high tibial osteotomy produces an extra-articular deformity. Neyret and colleagues⁷ reported difficulties in correcting angulations of 9° or more through soft-tissue release. Cameron and Welsh¹⁶ suggested pre–knee arthroplasty correction of the extra-articular deformity for malalignments of more than 15°. In cases of severe malalignment produced by an osteotomy, Katz and colleagues⁵ also suggested that a second osteotomy be performed to correct alignment before TKA.

For TKA after high tibial osteotomy, a neutral plateau resection removes more bone medially than laterally, creating medial laxity. Without correction of the tibial deformity, lateral release (or, as Krackow and Holtgrewe²⁰ advocated, medial advancement) is required for ligament stability. Both technically demanding options may not provide complete stability throughout the arc of motion. In addition, neither corrects for rotational or sagittal deformities (the concern with correcting an extra-articular deformity with intra-articular ligament balancing).

Another option is valgus tibial resection, which maintains native ligament balance at the cost of excessive valgus alignment. In the low-demand patient, a condylar constrained implant provides a means of correcting the malalignment with knee stability.^8,13,17 The increased restraint produces greater forces at the implant–bone interface and may risk early loosening.

The case presented here represents a unique situation of failed bilateral high tibial osteotomies with excessive valgus malalignment. In a similar situation, Papagelopoulos and colleagues²¹ suggested correcting fracture deformities before or at time of knee arthroplasty. Yoshina and colleagues²² reported using a stemmed tibial component with TKA in treating nonunion of a high tibial osteotomy. As mentioned, Katz and colleagues⁵ and Neyret and colleagues⁷ suggested preoperative correction of the osteotomy in cases of severe malalignment. Others have suggested combining recorrection osteotomy and knee arthroplasty in either consecutive operations or a single operation.^23-26 Wolff and colleagues²⁷ and Uchinou and colleagues²⁸ described recorrection osteotomy performed concurrent with TKA. The present article is the first to report a case involving concurrent bilateral recorrection osteotomy and TKA.

In one setting, the recorrection osteotomy is performed after the bony cuts are made for the TKA. The initial tibial plateau resection is performed in valgus at the same degree of malalignment as the osteotomy. This allows the plane of the tibial resection to parallel the floor once the recorrection is finished. With use of a tibial stem crossing the osteotomy site and a derotation plate, adequate fixation of the osteotomy is obtained. The recorrection osteotomy prevents the ligaments from overlengthening, allows the native ligament balance of the knee, and preserves the PCL—which lets the surgeon obtain ligament balance for the TKA throughout the arc of motion, avoiding midstance instabilities and achieving knee alignment rotationally and in the coronal and sagittal planes.

The TKA used in the present case was a PCL-retaining design. Both posterior-stabilized and PCL-retaining designs are reasonable options for use in combination with recorrection osteotomy. A stemmed tibial component is needed to cross the osteotomy site. In our patient’s case, use of a PCL-retaining design was based on surgeon preference and experience.

Patella infera has been noted as a problem in studies on converting high tibial osteotomy to TKA.^9,12,29 A postulated cause is scarring of the infrapatellar tendon after high tibial osteotomy. In addition, a higher incidence of lateral retinacular release has been identified.^9-11 Patella infera did not occur in either knee in the present case, and lateral release was not required.

Our patient’s lateral radiographs (Figures 4A, 4B) showed persistence of the osteotomy plane anterior to the tibia. The osteotomy healed posteriorly but not completely anteriorly. This raises the issue of risk for nonunion when recorrection osteotomy is performed with TKA. Use of a stemmed tibial implant with a derotation plate provides the benefit of intramedullary fixation for the recorrection osteotomy. If the recorrection osteotomy were performed in a separate setting before TKA, plate fixation would be the primary fixation option. Should nonunion occur at the recorrection osteotomy site, revision of the tibial plateau with a new stemmed implant would be required in combination with plate fixation. Madelaine and colleagues³⁰ reported on a series of 15 severe varus knees treated with both osteotomy and TKA. Two nonunions occurred. Fixation was a staple in one case and a cement wedge in the other. Risk for nonunion may be reduced with the combination of stemmed tibial implant and internal fixation with a derotation plate. Protective weight-bearing is recommended for the first 6 postoperative weeks.

Conclusion

Ligament imbalances produced by high tibial osteotomy and exacerbated by conversion to TKA are difficult to address. In this report, we have described successful single-stage high tibial osteotomy recorrection and TKA performed bilaterally in separate settings. With use of a stemmed tibial component and a derotation plate, solid fixation was obtained with an excellent clinical outcome. The malalignment was corrected while ligament balance was maintained for a PCL-retaining TKA design.

Wound complications (eg, delayed wound healing, blisters, prolonged drainage) have been reported in up to 30% of patients who undergo elective total joint arthroplasty (TJA).^1-6 Wound complications increase resource utilization, lengthen hospital stays, and increase costs.^7-9 Prolonged wound healing and persistent wound drainage are also harbingers of both superficial and deep surgical site infections.^5-11

In several studies, wound complications after TJA were the primary reason for hospital readmissions.^12-15 As part of the Patient Protection and Affordable Care Act, hospitals will be penalized by the Centers for Medicaid & Medicare Services for unplanned hospital readmissions within 30 days after TJA. It is imperative, then, to reduce the risk factors and complications associated with surgical site infections to decrease unplanned readmissions.

Historically, little attention has been given to the role of surgical dressings and the effect of dressings on wound healing. Although many subspecialties (eg, cardiothoracic surgery, general surgery) have reported benefits in using occlusive dressings, adoption in TJA has been slow.^16-18 At our institution about 5 years ago, we began using an occlusive silver-impregnated barrier dressing based on preliminary data from studies showing benefits of occlusive dressings in TJA.^19,20

We conducted a study to determine if use of occlusive antimicrobial barrier dressings decreases rates of wound complications in TJA. We had 3 research questions: Compared with standard surgical dressings, are occlusive dressings associated with decreased rates of wound complications after TJA? Is there a difference in number of dressing changes required between the 2 dressing types? Is satisfaction higher for patients with occlusive dressings than for patients with standard dressings?

Patients and Methods

This randomized controlled trial (RCT) was reviewed and approved by the Institutional Review Board at Carolinas Healthcare. Patients were randomized by the research staff using a parallel, 1:1 allocation method. The randomization table was generated using a random number generator.

An a priori sample size estimate was made using a 2-tailed Fisher exact test with a .05 level of significance. Based on a study by Clarke and colleagues,²¹ we estimated the incidence of wound problems at 3% in the occlusive dressing (study) group and 13% in the standard dressing (control) group. We determined that 260 participants (130 per group) would be needed to achieve 80% power. We considered a 15% attrition rate for a total enrollment goal of 300 study participants (150 per group).

Between December 2010 and January 2013, patients presenting for either primary total hip arthroplasty (THA) or primary total knee arthroplasty (TKA) were recruited to participate in the study. Eligibility criteria (Table 1) were reviewed, and patients were enrolled by the senior surgeons, Dr. Springer, Dr. Beaver, Dr. Griffin, and Dr. Mason. All eligible participants who provided informed consent were randomized to receive either an occlusive antimicrobial barrier dressing (Aquacel Ag, ConvaTec) or standard surgical dressing (Primapore, Smith & Nephew). The occlusive dressing (Figure 1) consists of an outer barrier layer of hydrocolloid and a central island of hydrofiber, which absorbs and locks in any wound exudate within the fibers and prevents the creation of an overly moist wound environment that can lead to skin maceration and wound breakdown. In addition, the hydrofibers are embedded with ionic silver, which is released only at the site of wound exudate, or drainage; thus, there is no continuous exposure of the entire wound to silver. The standard dressing (Figure 2) consists of a central island of gauze enclosed in low-allergy acrylic adhesive tape.

All surgical dressings were placed over a closed incision in a sterile environment in the operating room after the procedure. The groups’ wound closures were identical.

A posterior approach was used for all THAs. The deep fascia was closed with a running barbed suture (Quill, Angiotech), the deep subcutaneous tissue with No. 1 Vicryl suture (Ethicon), and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch (Ethicon) was placed in the subcuticular layer and was followed with a skin adhesive (Dermabond, Ethicon). A closed suction drain, removed on postoperative day (POD) 1, was used for all THAs.

A standard medial parapatellar arthrotomy was used for all TKAs. The arthrotomy was closed with a running barbed suture, the deep subcutaneous tissue with No. 1 Vicryl suture, and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch was placed in the subcuticular layer and was followed with a skin adhesive. A closed suction drain was also used. In addition, a compressive wrap was placed over the dressing in the operating room and was removed the next morning. During the hospital stay, the surgical site was evaluated daily with a standard wound evaluation form.

 In the standard dressing group, the bandage was removed for wound evaluation on POD 2, and the dressing was changed every other day during the hospital stay. The dressing was also changed as needed for wound drainage (Figure 3) or other minor wound-healing concerns.

In the occlusive dressing group, the dressing design allowed the dressing to remain in place for about 7 days. It was removed by a home health nurse during a visit closest to but not before the 7-day mark. In addition, it was changed at surgeon discretion if there were concerns about wound drainage or wound healing. For the occlusive barrier, wound drainage was evaluated by strike-through of drainage on the back side of the dressing (Figure 4). If more than 50% of the dressing was saturated, the bandage was changed and the wound evaluated. If there were no immediate concerns about wound complications (eg, infection, blistering), a new occlusive dressing was placed. Because the occlusive dressing was waterproof, patients in the study group were able to shower immediately after surgery. In the control group, patients were allowed to shower if the surgical dressing was kept dry, as the bandage was not waterproof.

Per the study protocol, all patients were discharged home and followed by a single home health agency. Mean hospital stay was 3 days (range, 0-8 days), which did not differ significantly between groups (P = .133). All home health nurses were trained in evaluation of postsurgical wounds and were aware of the study requirements. The nurses visited all patients 3 days a week until the scheduled 4-week postoperative follow-up with the treating physician or physician assistant. At each visit, the nurse evaluated the wound and surrounding skin using a standard wound document. Dressings were changed based on the criteria we have described. Concerns about wound status (eg, drainage, blistering, erythema) prompted removal of the dressing for further evaluation. The physician was notified of concerns about wound healing, which prompted an office visit for evaluation. The dressing remained in place for a minimum of 7 days but in all cases was removed as close to 7 days as possible, depending on the scheduled nursing visits. Once uneventful wound healing was complete, no further dressing was required. A final wound evaluation was conducted by the surgeon at the 4-week postoperative evaluation.

The primary outcome measure was wound complication (dichotomous variable). Wounds were assessed by describing the amount, type, and color of exudate (Figure 5). The appearance of the wound margins and the surrounding skin was also assessed. Because wounds could not be directly visualized in the occlusive dressing group, drainage (indicated by strike-through) was used as a measure of possible wound complications, prompting removal and full evaluation.

 Secondary endpoints included additional wound treatment or surgical procedures for wound complications, number of dressing changes, and patient satisfaction. Patients completed a satisfaction questionnaire at each wound assessment (Figure 6). Using a visual analog scale (VAS), they rated their satisfaction with their ability to perform activities of daily living (personal hygiene, change clothes, sit comfortably, sleep comfortably), drawing a line on the VAS at a point between 0 (totally unsatisfied) and 100 (totally satisfied) for each satisfaction measure. This line was measured and recorded by the study coordinator. The 4 satisfaction measures were averaged for a composite satisfaction measure.

All statistical analyses were conducted using SAS Version 9.2 (SAS Institute). Standard univariate descriptive statistics (means, standard deviations, frequencies, proportions) were calculated and reported. Differences in mean values for continuous data were assessed with independent t test or Wilcoxon rank sum test. Chi-square test and Fisher exact test were used to determine differences between groups for categorical or dichotomous variables. A significance level of .05 was used for all statistical tests.

Results

The 300 patients who consented to participate in the study were randomized to receive either occlusive dressing or standard dressing. After randomization, 38 patients (15 occlusive, 23 standard) were withdrawn from the study (Table 2), leaving a final dataset of 262 patients, 141 in the occlusive group (67 THAs, 74 TKAs) and 121 in the standard group (49 THAs, 72 TKAs). There were no differences in proportion of THAs or TKAs, age, sex, or body mass index between the occlusive and standard groups (Table 3).

There were statistically significantly (P = .015) fewer wound complications in the occlusive dressing group (10%) than in the standard dressing group (22%). Blisters at or around the wound site were reported in significantly (P = .026) fewer patients with occlusive dressing (1/141, 0.7%) than standard dressing (7/121, 6%). Additional wound care was required in 9 patients (7%) in the standard group and 6 patients (4%) in the occlusive group (P = .27). Two patients (1.7%) in the standard group were readmitted for treatment of wound dehiscence; no one in the occlusive group was readmitted to the hospital or had to return to the operating room for treatment of a wound complication. The difference was not statistically significant (P = .13). There were also no significant (P = .81) differences in rate of wound complications between THA and TKA patients.

There were statistically significantly (P < .0001) fewer dressing changes in the occlusive dressing group. Mean number of dressing changes was 0.14 (median, 0; interquartile range, 0-0) in the occlusive group and 2.8 (median, 2; interquartile range, 1-3) in the standard group.

Compared with patients in the standard dressing group, patients in the occlusive dressing group reported significantly higher satisfaction scores. Mean overall patient satisfaction score was 92 in the occlusive group and 81 in the standard group (P < .0001). Patients in the occlusive group were more satisfied with their ability to take care of their personal hygiene, to change clothes, and to sit and sleep comfortably (Table 4).

Discussion

Wound complications after TJA are common, occurring in up to 30% of patients,^1-6 and are associated with development of superficial and deep surgical site infections, increased resource utilization, and longer hospital stays.^5-11 Although the role of surgical dressings has received little attention in TJA practice, other subspecialties have found that occlusive barrier dressings can reduce wound complications and promote wound healing.^16,17 Mitotic cell division and leukocyte activity, which are critical in wound healing, increase under occlusive dressings. This cellular activity is disrupted with every dressing change, delaying wound healing (biological activity takes 3-4 hours to resume).²² In addition, occlusive dressings increase hypoxia, which promotes angiogenesis and accelerates wound healing.²³

Despite being a prospective RCT, this study had several limitations. Because of the need to evaluate wounds and obvious differences between the 2 dressings (eg, color, ability to shower), it was not possible to blind the patient or surgeon to the dressing used. When rating satisfaction, patients were not able to directly compare the 2 dressings. The primary endpoint of the study was the complication rate; however, the deep periprosthetic infection rate may be a superior endpoint and would require a much larger study. Although we assumed that wound complications may be harbingers for periprosthetic infections, no patient in either group developed periprosthetic infection. Therefore, we cannot conclude that surgical dressings play a role in reducing infections. In addition, as the standard dressing was changed on POD 2 (per standard protocol) and the occlusive dressing could remain in place for up to 7 days, there was a selection bias in the evaluation of the number of dressing changes. However, given the characteristics of the standard dressing (eg, tape, gauze, nonocclusive), leaving it in place after POD 2 is not optimal. Therefore, we would expect to see a difference in the number of dressing changes. We think this comparison remains valid, as occlusive dressings were changed when there were indications of wound problems (eg, excessive drainage [strike-through], surrounding erythema, blistering). With an average of less than 1 dressing change in the occlusive group, we think this is a surrogate for uneventful wound healing and decreased wound complication, and our data support this. It is also important to test both dressing durability and patient tolerance for wearing a single dressing for 7 days.

Our RCT results showed that, compared with a standard dressing, an occlusive antimicrobial dressing was associated with a significant decrease in overall wound complications and blisters. These findings are similar to those of other studies of occlusive dressings in a number of surgical subspecialties.^16,18 In an RCT of 200 patients who underwent elective and nonelective hip and knee surgery and were randomized to either absorbent perforated dressing with adhesive border (Cutiplast, Smith & Nephew) or Aquacel (ConvaTec) covered with vapor-permeable dressing (Tegaderm, 3M), Ravenscroft and colleagues²⁰ found that Aquacel-plus-Tegaderm was 5.8 times more likely than Cutiplast to produce an uncompromised wound. Similarly, in an RCT of hydrofiber (Aquacel) and central pad (Mepore, Mölnlycke) dressings after primary THA and TKA, Abuzakuk and colleagues¹⁹ found significantly fewer dressing changes (43% vs 77%) and blisters (13% vs 26%) in the hydrofiber group than in the pad group.

Hopper and colleagues²⁴ compared 50 consecutive patients treated with modern dressings (Aquacel) with 50 historical control patients treated with traditional surgical dressings (Mepore). Blisters developed in 20% of the patients in the traditional group and 4% of patients in the modern group (P = .028). The authors concluded that adverse outcomes of wound healing can be minimized with modern dressings.

A recent retrospective study by Cai and colleagues²⁵ evaluated the incidence of acute periprosthetic infection (≤3 months after surgery) with use of occlusive (Aquacel) and standard dressings. Incidence of acute periprosthetic infection was 0.44% in the occlusive group and 1.7% in the standard group (P = .005). Incidence of wound-healing problems was not evaluated.

Our second aim in the present study was to evaluate the number of dressing changes required. There were significantly fewer dressing changes in the occlusive dressing group than in the standard dressing group. Therefore, wear time (amount of time a single dressing remains in place) was substantially longer for the occlusive group. In the study by Hopper and colleagues,²⁴ wear time was significantly shorter for the traditional dressing than for the modern dressing (2 vs 7 days; P < .001), and the traditional dressing required more changes (3 vs 0; P < .001).

These findings are important for several reasons. Standard surgical dressings often require frequent changes. If left in place, they create an excessively moist wound environment that promotes blistering and delays wound healing. However, frequent dressing changes expose the wound and increase the risk for surgical site infection.²⁶ A barrier dressing left in place from time of surgery prevents bacteria from entering and contaminating a healing wound. A study by Clarke and colleagues²¹ demonstrated higher skin colonization rates for patients who had dressings changed on POD 1 than for patients who had their first dressing change on POD 6.

Our third study aim was to evaluate patient satisfaction with surgical dressings. The orthopedic literature has little on this topic.²³ Blisters and other wound complications can negatively affect satisfaction.^2,3 Our data showed significant improvement in satisfaction, particularly regarding sterility and hygiene.

Other surgical subspecialties have found similar improvement in patient satisfaction with occlusive barrier dressings. In an RCT of 88 pediatric patients, Rasmussen and colleagues²⁷ found that patients reported significantly less pain during changes of an occlusive adhesive dressing (Duoderm, ConvaTec) than during changes of a conventional Steristrip (3M) plus Cutiplast. According to the authors, the occlusive wound dressing seemed to minimize the physical and psychological trauma to the infant or child and lessen disruption of the child’s and the parents’ daily routines, because the children could be bathed immediately after surgery.

Our study did not specifically address cost. Cai and colleagues²⁵ estimated that, if the Aquacel dressing were routinely used in every hip and knee arthroplasty, it would add about $27 million in cost. However, this must be balanced by the cost of managing infection after TJA. In the United States, at an estimated $50,000 to $100,000 per case and an annual incidence of 1% to 2%, the low-end cost for the treatment of periprosthetic infection would be $500 million.²⁸ Cai and colleagues²⁵ found a 4-fold reduction in periprosthetic infection when use of occlusive dressings was implemented. In addition, wound complications remain the number one reason for hospital readmission after TJA.^12,13 Cost of hospital readmission, as well as financial penalties to institutions for unplanned readmission for wound complications, must be considered.

Conclusion

Our RCT results demonstrated that use of occlusive antimicrobial barrier dressings (vs standard surgical dressings) significantly reduced wound complications and dressing changes and improved overall patient satisfaction. These findings are similar to those in the literature on TJA and other surgical subspecialties. We conclude that occlusive surgical dressings reduce wound complications after TJA.

Wound complications (eg, delayed wound healing, blisters, prolonged drainage) have been reported in up to 30% of patients who undergo elective total joint arthroplasty (TJA).^1-6 Wound complications increase resource utilization, lengthen hospital stays, and increase costs.^7-9 Prolonged wound healing and persistent wound drainage are also harbingers of both superficial and deep surgical site infections.^5-11

In several studies, wound complications after TJA were the primary reason for hospital readmissions.^12-15 As part of the Patient Protection and Affordable Care Act, hospitals will be penalized by the Centers for Medicaid & Medicare Services for unplanned hospital readmissions within 30 days after TJA. It is imperative, then, to reduce the risk factors and complications associated with surgical site infections to decrease unplanned readmissions.

Historically, little attention has been given to the role of surgical dressings and the effect of dressings on wound healing. Although many subspecialties (eg, cardiothoracic surgery, general surgery) have reported benefits in using occlusive dressings, adoption in TJA has been slow.^16-18 At our institution about 5 years ago, we began using an occlusive silver-impregnated barrier dressing based on preliminary data from studies showing benefits of occlusive dressings in TJA.^19,20

We conducted a study to determine if use of occlusive antimicrobial barrier dressings decreases rates of wound complications in TJA. We had 3 research questions: Compared with standard surgical dressings, are occlusive dressings associated with decreased rates of wound complications after TJA? Is there a difference in number of dressing changes required between the 2 dressing types? Is satisfaction higher for patients with occlusive dressings than for patients with standard dressings?

Patients and Methods

This randomized controlled trial (RCT) was reviewed and approved by the Institutional Review Board at Carolinas Healthcare. Patients were randomized by the research staff using a parallel, 1:1 allocation method. The randomization table was generated using a random number generator.

An a priori sample size estimate was made using a 2-tailed Fisher exact test with a .05 level of significance. Based on a study by Clarke and colleagues,²¹ we estimated the incidence of wound problems at 3% in the occlusive dressing (study) group and 13% in the standard dressing (control) group. We determined that 260 participants (130 per group) would be needed to achieve 80% power. We considered a 15% attrition rate for a total enrollment goal of 300 study participants (150 per group).

Between December 2010 and January 2013, patients presenting for either primary total hip arthroplasty (THA) or primary total knee arthroplasty (TKA) were recruited to participate in the study. Eligibility criteria (Table 1) were reviewed, and patients were enrolled by the senior surgeons, Dr. Springer, Dr. Beaver, Dr. Griffin, and Dr. Mason. All eligible participants who provided informed consent were randomized to receive either an occlusive antimicrobial barrier dressing (Aquacel Ag, ConvaTec) or standard surgical dressing (Primapore, Smith & Nephew). The occlusive dressing (Figure 1) consists of an outer barrier layer of hydrocolloid and a central island of hydrofiber, which absorbs and locks in any wound exudate within the fibers and prevents the creation of an overly moist wound environment that can lead to skin maceration and wound breakdown. In addition, the hydrofibers are embedded with ionic silver, which is released only at the site of wound exudate, or drainage; thus, there is no continuous exposure of the entire wound to silver. The standard dressing (Figure 2) consists of a central island of gauze enclosed in low-allergy acrylic adhesive tape.

All surgical dressings were placed over a closed incision in a sterile environment in the operating room after the procedure. The groups’ wound closures were identical.

A posterior approach was used for all THAs. The deep fascia was closed with a running barbed suture (Quill, Angiotech), the deep subcutaneous tissue with No. 1 Vicryl suture (Ethicon), and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch (Ethicon) was placed in the subcuticular layer and was followed with a skin adhesive (Dermabond, Ethicon). A closed suction drain, removed on postoperative day (POD) 1, was used for all THAs.

A standard medial parapatellar arthrotomy was used for all TKAs. The arthrotomy was closed with a running barbed suture, the deep subcutaneous tissue with No. 1 Vicryl suture, and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch was placed in the subcuticular layer and was followed with a skin adhesive. A closed suction drain was also used. In addition, a compressive wrap was placed over the dressing in the operating room and was removed the next morning. During the hospital stay, the surgical site was evaluated daily with a standard wound evaluation form.

 In the standard dressing group, the bandage was removed for wound evaluation on POD 2, and the dressing was changed every other day during the hospital stay. The dressing was also changed as needed for wound drainage (Figure 3) or other minor wound-healing concerns.

In the occlusive dressing group, the dressing design allowed the dressing to remain in place for about 7 days. It was removed by a home health nurse during a visit closest to but not before the 7-day mark. In addition, it was changed at surgeon discretion if there were concerns about wound drainage or wound healing. For the occlusive barrier, wound drainage was evaluated by strike-through of drainage on the back side of the dressing (Figure 4). If more than 50% of the dressing was saturated, the bandage was changed and the wound evaluated. If there were no immediate concerns about wound complications (eg, infection, blistering), a new occlusive dressing was placed. Because the occlusive dressing was waterproof, patients in the study group were able to shower immediately after surgery. In the control group, patients were allowed to shower if the surgical dressing was kept dry, as the bandage was not waterproof.

Per the study protocol, all patients were discharged home and followed by a single home health agency. Mean hospital stay was 3 days (range, 0-8 days), which did not differ significantly between groups (P = .133). All home health nurses were trained in evaluation of postsurgical wounds and were aware of the study requirements. The nurses visited all patients 3 days a week until the scheduled 4-week postoperative follow-up with the treating physician or physician assistant. At each visit, the nurse evaluated the wound and surrounding skin using a standard wound document. Dressings were changed based on the criteria we have described. Concerns about wound status (eg, drainage, blistering, erythema) prompted removal of the dressing for further evaluation. The physician was notified of concerns about wound healing, which prompted an office visit for evaluation. The dressing remained in place for a minimum of 7 days but in all cases was removed as close to 7 days as possible, depending on the scheduled nursing visits. Once uneventful wound healing was complete, no further dressing was required. A final wound evaluation was conducted by the surgeon at the 4-week postoperative evaluation.

The primary outcome measure was wound complication (dichotomous variable). Wounds were assessed by describing the amount, type, and color of exudate (Figure 5). The appearance of the wound margins and the surrounding skin was also assessed. Because wounds could not be directly visualized in the occlusive dressing group, drainage (indicated by strike-through) was used as a measure of possible wound complications, prompting removal and full evaluation.

 Secondary endpoints included additional wound treatment or surgical procedures for wound complications, number of dressing changes, and patient satisfaction. Patients completed a satisfaction questionnaire at each wound assessment (Figure 6). Using a visual analog scale (VAS), they rated their satisfaction with their ability to perform activities of daily living (personal hygiene, change clothes, sit comfortably, sleep comfortably), drawing a line on the VAS at a point between 0 (totally unsatisfied) and 100 (totally satisfied) for each satisfaction measure. This line was measured and recorded by the study coordinator. The 4 satisfaction measures were averaged for a composite satisfaction measure.

All statistical analyses were conducted using SAS Version 9.2 (SAS Institute). Standard univariate descriptive statistics (means, standard deviations, frequencies, proportions) were calculated and reported. Differences in mean values for continuous data were assessed with independent t test or Wilcoxon rank sum test. Chi-square test and Fisher exact test were used to determine differences between groups for categorical or dichotomous variables. A significance level of .05 was used for all statistical tests.

Results

The 300 patients who consented to participate in the study were randomized to receive either occlusive dressing or standard dressing. After randomization, 38 patients (15 occlusive, 23 standard) were withdrawn from the study (Table 2), leaving a final dataset of 262 patients, 141 in the occlusive group (67 THAs, 74 TKAs) and 121 in the standard group (49 THAs, 72 TKAs). There were no differences in proportion of THAs or TKAs, age, sex, or body mass index between the occlusive and standard groups (Table 3).

There were statistically significantly (P = .015) fewer wound complications in the occlusive dressing group (10%) than in the standard dressing group (22%). Blisters at or around the wound site were reported in significantly (P = .026) fewer patients with occlusive dressing (1/141, 0.7%) than standard dressing (7/121, 6%). Additional wound care was required in 9 patients (7%) in the standard group and 6 patients (4%) in the occlusive group (P = .27). Two patients (1.7%) in the standard group were readmitted for treatment of wound dehiscence; no one in the occlusive group was readmitted to the hospital or had to return to the operating room for treatment of a wound complication. The difference was not statistically significant (P = .13). There were also no significant (P = .81) differences in rate of wound complications between THA and TKA patients.

There were statistically significantly (P < .0001) fewer dressing changes in the occlusive dressing group. Mean number of dressing changes was 0.14 (median, 0; interquartile range, 0-0) in the occlusive group and 2.8 (median, 2; interquartile range, 1-3) in the standard group.

Compared with patients in the standard dressing group, patients in the occlusive dressing group reported significantly higher satisfaction scores. Mean overall patient satisfaction score was 92 in the occlusive group and 81 in the standard group (P < .0001). Patients in the occlusive group were more satisfied with their ability to take care of their personal hygiene, to change clothes, and to sit and sleep comfortably (Table 4).

Discussion

Wound complications after TJA are common, occurring in up to 30% of patients,^1-6 and are associated with development of superficial and deep surgical site infections, increased resource utilization, and longer hospital stays.^5-11 Although the role of surgical dressings has received little attention in TJA practice, other subspecialties have found that occlusive barrier dressings can reduce wound complications and promote wound healing.^16,17 Mitotic cell division and leukocyte activity, which are critical in wound healing, increase under occlusive dressings. This cellular activity is disrupted with every dressing change, delaying wound healing (biological activity takes 3-4 hours to resume).²² In addition, occlusive dressings increase hypoxia, which promotes angiogenesis and accelerates wound healing.²³

Despite being a prospective RCT, this study had several limitations. Because of the need to evaluate wounds and obvious differences between the 2 dressings (eg, color, ability to shower), it was not possible to blind the patient or surgeon to the dressing used. When rating satisfaction, patients were not able to directly compare the 2 dressings. The primary endpoint of the study was the complication rate; however, the deep periprosthetic infection rate may be a superior endpoint and would require a much larger study. Although we assumed that wound complications may be harbingers for periprosthetic infections, no patient in either group developed periprosthetic infection. Therefore, we cannot conclude that surgical dressings play a role in reducing infections. In addition, as the standard dressing was changed on POD 2 (per standard protocol) and the occlusive dressing could remain in place for up to 7 days, there was a selection bias in the evaluation of the number of dressing changes. However, given the characteristics of the standard dressing (eg, tape, gauze, nonocclusive), leaving it in place after POD 2 is not optimal. Therefore, we would expect to see a difference in the number of dressing changes. We think this comparison remains valid, as occlusive dressings were changed when there were indications of wound problems (eg, excessive drainage [strike-through], surrounding erythema, blistering). With an average of less than 1 dressing change in the occlusive group, we think this is a surrogate for uneventful wound healing and decreased wound complication, and our data support this. It is also important to test both dressing durability and patient tolerance for wearing a single dressing for 7 days.

Our RCT results showed that, compared with a standard dressing, an occlusive antimicrobial dressing was associated with a significant decrease in overall wound complications and blisters. These findings are similar to those of other studies of occlusive dressings in a number of surgical subspecialties.^16,18 In an RCT of 200 patients who underwent elective and nonelective hip and knee surgery and were randomized to either absorbent perforated dressing with adhesive border (Cutiplast, Smith & Nephew) or Aquacel (ConvaTec) covered with vapor-permeable dressing (Tegaderm, 3M), Ravenscroft and colleagues²⁰ found that Aquacel-plus-Tegaderm was 5.8 times more likely than Cutiplast to produce an uncompromised wound. Similarly, in an RCT of hydrofiber (Aquacel) and central pad (Mepore, Mölnlycke) dressings after primary THA and TKA, Abuzakuk and colleagues¹⁹ found significantly fewer dressing changes (43% vs 77%) and blisters (13% vs 26%) in the hydrofiber group than in the pad group.

Hopper and colleagues²⁴ compared 50 consecutive patients treated with modern dressings (Aquacel) with 50 historical control patients treated with traditional surgical dressings (Mepore). Blisters developed in 20% of the patients in the traditional group and 4% of patients in the modern group (P = .028). The authors concluded that adverse outcomes of wound healing can be minimized with modern dressings.

A recent retrospective study by Cai and colleagues²⁵ evaluated the incidence of acute periprosthetic infection (≤3 months after surgery) with use of occlusive (Aquacel) and standard dressings. Incidence of acute periprosthetic infection was 0.44% in the occlusive group and 1.7% in the standard group (P = .005). Incidence of wound-healing problems was not evaluated.

Our second aim in the present study was to evaluate the number of dressing changes required. There were significantly fewer dressing changes in the occlusive dressing group than in the standard dressing group. Therefore, wear time (amount of time a single dressing remains in place) was substantially longer for the occlusive group. In the study by Hopper and colleagues,²⁴ wear time was significantly shorter for the traditional dressing than for the modern dressing (2 vs 7 days; P < .001), and the traditional dressing required more changes (3 vs 0; P < .001).

These findings are important for several reasons. Standard surgical dressings often require frequent changes. If left in place, they create an excessively moist wound environment that promotes blistering and delays wound healing. However, frequent dressing changes expose the wound and increase the risk for surgical site infection.²⁶ A barrier dressing left in place from time of surgery prevents bacteria from entering and contaminating a healing wound. A study by Clarke and colleagues²¹ demonstrated higher skin colonization rates for patients who had dressings changed on POD 1 than for patients who had their first dressing change on POD 6.

Our third study aim was to evaluate patient satisfaction with surgical dressings. The orthopedic literature has little on this topic.²³ Blisters and other wound complications can negatively affect satisfaction.^2,3 Our data showed significant improvement in satisfaction, particularly regarding sterility and hygiene.

Other surgical subspecialties have found similar improvement in patient satisfaction with occlusive barrier dressings. In an RCT of 88 pediatric patients, Rasmussen and colleagues²⁷ found that patients reported significantly less pain during changes of an occlusive adhesive dressing (Duoderm, ConvaTec) than during changes of a conventional Steristrip (3M) plus Cutiplast. According to the authors, the occlusive wound dressing seemed to minimize the physical and psychological trauma to the infant or child and lessen disruption of the child’s and the parents’ daily routines, because the children could be bathed immediately after surgery.

Our study did not specifically address cost. Cai and colleagues²⁵ estimated that, if the Aquacel dressing were routinely used in every hip and knee arthroplasty, it would add about $27 million in cost. However, this must be balanced by the cost of managing infection after TJA. In the United States, at an estimated $50,000 to $100,000 per case and an annual incidence of 1% to 2%, the low-end cost for the treatment of periprosthetic infection would be $500 million.²⁸ Cai and colleagues²⁵ found a 4-fold reduction in periprosthetic infection when use of occlusive dressings was implemented. In addition, wound complications remain the number one reason for hospital readmission after TJA.^12,13 Cost of hospital readmission, as well as financial penalties to institutions for unplanned readmission for wound complications, must be considered.

Conclusion

Our RCT results demonstrated that use of occlusive antimicrobial barrier dressings (vs standard surgical dressings) significantly reduced wound complications and dressing changes and improved overall patient satisfaction. These findings are similar to those in the literature on TJA and other surgical subspecialties. We conclude that occlusive surgical dressings reduce wound complications after TJA.

Wound complications (eg, delayed wound healing, blisters, prolonged drainage) have been reported in up to 30% of patients who undergo elective total joint arthroplasty (TJA).^1-6 Wound complications increase resource utilization, lengthen hospital stays, and increase costs.^7-9 Prolonged wound healing and persistent wound drainage are also harbingers of both superficial and deep surgical site infections.^5-11

In several studies, wound complications after TJA were the primary reason for hospital readmissions.^12-15 As part of the Patient Protection and Affordable Care Act, hospitals will be penalized by the Centers for Medicaid & Medicare Services for unplanned hospital readmissions within 30 days after TJA. It is imperative, then, to reduce the risk factors and complications associated with surgical site infections to decrease unplanned readmissions.

Historically, little attention has been given to the role of surgical dressings and the effect of dressings on wound healing. Although many subspecialties (eg, cardiothoracic surgery, general surgery) have reported benefits in using occlusive dressings, adoption in TJA has been slow.^16-18 At our institution about 5 years ago, we began using an occlusive silver-impregnated barrier dressing based on preliminary data from studies showing benefits of occlusive dressings in TJA.^19,20

We conducted a study to determine if use of occlusive antimicrobial barrier dressings decreases rates of wound complications in TJA. We had 3 research questions: Compared with standard surgical dressings, are occlusive dressings associated with decreased rates of wound complications after TJA? Is there a difference in number of dressing changes required between the 2 dressing types? Is satisfaction higher for patients with occlusive dressings than for patients with standard dressings?

Patients and Methods

This randomized controlled trial (RCT) was reviewed and approved by the Institutional Review Board at Carolinas Healthcare. Patients were randomized by the research staff using a parallel, 1:1 allocation method. The randomization table was generated using a random number generator.

An a priori sample size estimate was made using a 2-tailed Fisher exact test with a .05 level of significance. Based on a study by Clarke and colleagues,²¹ we estimated the incidence of wound problems at 3% in the occlusive dressing (study) group and 13% in the standard dressing (control) group. We determined that 260 participants (130 per group) would be needed to achieve 80% power. We considered a 15% attrition rate for a total enrollment goal of 300 study participants (150 per group).

Between December 2010 and January 2013, patients presenting for either primary total hip arthroplasty (THA) or primary total knee arthroplasty (TKA) were recruited to participate in the study. Eligibility criteria (Table 1) were reviewed, and patients were enrolled by the senior surgeons, Dr. Springer, Dr. Beaver, Dr. Griffin, and Dr. Mason. All eligible participants who provided informed consent were randomized to receive either an occlusive antimicrobial barrier dressing (Aquacel Ag, ConvaTec) or standard surgical dressing (Primapore, Smith & Nephew). The occlusive dressing (Figure 1) consists of an outer barrier layer of hydrocolloid and a central island of hydrofiber, which absorbs and locks in any wound exudate within the fibers and prevents the creation of an overly moist wound environment that can lead to skin maceration and wound breakdown. In addition, the hydrofibers are embedded with ionic silver, which is released only at the site of wound exudate, or drainage; thus, there is no continuous exposure of the entire wound to silver. The standard dressing (Figure 2) consists of a central island of gauze enclosed in low-allergy acrylic adhesive tape.

All surgical dressings were placed over a closed incision in a sterile environment in the operating room after the procedure. The groups’ wound closures were identical.

A posterior approach was used for all THAs. The deep fascia was closed with a running barbed suture (Quill, Angiotech), the deep subcutaneous tissue with No. 1 Vicryl suture (Ethicon), and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch (Ethicon) was placed in the subcuticular layer and was followed with a skin adhesive (Dermabond, Ethicon). A closed suction drain, removed on postoperative day (POD) 1, was used for all THAs.

A standard medial parapatellar arthrotomy was used for all TKAs. The arthrotomy was closed with a running barbed suture, the deep subcutaneous tissue with No. 1 Vicryl suture, and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch was placed in the subcuticular layer and was followed with a skin adhesive. A closed suction drain was also used. In addition, a compressive wrap was placed over the dressing in the operating room and was removed the next morning. During the hospital stay, the surgical site was evaluated daily with a standard wound evaluation form.

 In the standard dressing group, the bandage was removed for wound evaluation on POD 2, and the dressing was changed every other day during the hospital stay. The dressing was also changed as needed for wound drainage (Figure 3) or other minor wound-healing concerns.

In the occlusive dressing group, the dressing design allowed the dressing to remain in place for about 7 days. It was removed by a home health nurse during a visit closest to but not before the 7-day mark. In addition, it was changed at surgeon discretion if there were concerns about wound drainage or wound healing. For the occlusive barrier, wound drainage was evaluated by strike-through of drainage on the back side of the dressing (Figure 4). If more than 50% of the dressing was saturated, the bandage was changed and the wound evaluated. If there were no immediate concerns about wound complications (eg, infection, blistering), a new occlusive dressing was placed. Because the occlusive dressing was waterproof, patients in the study group were able to shower immediately after surgery. In the control group, patients were allowed to shower if the surgical dressing was kept dry, as the bandage was not waterproof.

Per the study protocol, all patients were discharged home and followed by a single home health agency. Mean hospital stay was 3 days (range, 0-8 days), which did not differ significantly between groups (P = .133). All home health nurses were trained in evaluation of postsurgical wounds and were aware of the study requirements. The nurses visited all patients 3 days a week until the scheduled 4-week postoperative follow-up with the treating physician or physician assistant. At each visit, the nurse evaluated the wound and surrounding skin using a standard wound document. Dressings were changed based on the criteria we have described. Concerns about wound status (eg, drainage, blistering, erythema) prompted removal of the dressing for further evaluation. The physician was notified of concerns about wound healing, which prompted an office visit for evaluation. The dressing remained in place for a minimum of 7 days but in all cases was removed as close to 7 days as possible, depending on the scheduled nursing visits. Once uneventful wound healing was complete, no further dressing was required. A final wound evaluation was conducted by the surgeon at the 4-week postoperative evaluation.

The primary outcome measure was wound complication (dichotomous variable). Wounds were assessed by describing the amount, type, and color of exudate (Figure 5). The appearance of the wound margins and the surrounding skin was also assessed. Because wounds could not be directly visualized in the occlusive dressing group, drainage (indicated by strike-through) was used as a measure of possible wound complications, prompting removal and full evaluation.

 Secondary endpoints included additional wound treatment or surgical procedures for wound complications, number of dressing changes, and patient satisfaction. Patients completed a satisfaction questionnaire at each wound assessment (Figure 6). Using a visual analog scale (VAS), they rated their satisfaction with their ability to perform activities of daily living (personal hygiene, change clothes, sit comfortably, sleep comfortably), drawing a line on the VAS at a point between 0 (totally unsatisfied) and 100 (totally satisfied) for each satisfaction measure. This line was measured and recorded by the study coordinator. The 4 satisfaction measures were averaged for a composite satisfaction measure.

All statistical analyses were conducted using SAS Version 9.2 (SAS Institute). Standard univariate descriptive statistics (means, standard deviations, frequencies, proportions) were calculated and reported. Differences in mean values for continuous data were assessed with independent t test or Wilcoxon rank sum test. Chi-square test and Fisher exact test were used to determine differences between groups for categorical or dichotomous variables. A significance level of .05 was used for all statistical tests.

Results

The 300 patients who consented to participate in the study were randomized to receive either occlusive dressing or standard dressing. After randomization, 38 patients (15 occlusive, 23 standard) were withdrawn from the study (Table 2), leaving a final dataset of 262 patients, 141 in the occlusive group (67 THAs, 74 TKAs) and 121 in the standard group (49 THAs, 72 TKAs). There were no differences in proportion of THAs or TKAs, age, sex, or body mass index between the occlusive and standard groups (Table 3).

There were statistically significantly (P = .015) fewer wound complications in the occlusive dressing group (10%) than in the standard dressing group (22%). Blisters at or around the wound site were reported in significantly (P = .026) fewer patients with occlusive dressing (1/141, 0.7%) than standard dressing (7/121, 6%). Additional wound care was required in 9 patients (7%) in the standard group and 6 patients (4%) in the occlusive group (P = .27). Two patients (1.7%) in the standard group were readmitted for treatment of wound dehiscence; no one in the occlusive group was readmitted to the hospital or had to return to the operating room for treatment of a wound complication. The difference was not statistically significant (P = .13). There were also no significant (P = .81) differences in rate of wound complications between THA and TKA patients.

There were statistically significantly (P < .0001) fewer dressing changes in the occlusive dressing group. Mean number of dressing changes was 0.14 (median, 0; interquartile range, 0-0) in the occlusive group and 2.8 (median, 2; interquartile range, 1-3) in the standard group.

Compared with patients in the standard dressing group, patients in the occlusive dressing group reported significantly higher satisfaction scores. Mean overall patient satisfaction score was 92 in the occlusive group and 81 in the standard group (P < .0001). Patients in the occlusive group were more satisfied with their ability to take care of their personal hygiene, to change clothes, and to sit and sleep comfortably (Table 4).

Discussion

Wound complications after TJA are common, occurring in up to 30% of patients,^1-6 and are associated with development of superficial and deep surgical site infections, increased resource utilization, and longer hospital stays.^5-11 Although the role of surgical dressings has received little attention in TJA practice, other subspecialties have found that occlusive barrier dressings can reduce wound complications and promote wound healing.^16,17 Mitotic cell division and leukocyte activity, which are critical in wound healing, increase under occlusive dressings. This cellular activity is disrupted with every dressing change, delaying wound healing (biological activity takes 3-4 hours to resume).²² In addition, occlusive dressings increase hypoxia, which promotes angiogenesis and accelerates wound healing.²³

Despite being a prospective RCT, this study had several limitations. Because of the need to evaluate wounds and obvious differences between the 2 dressings (eg, color, ability to shower), it was not possible to blind the patient or surgeon to the dressing used. When rating satisfaction, patients were not able to directly compare the 2 dressings. The primary endpoint of the study was the complication rate; however, the deep periprosthetic infection rate may be a superior endpoint and would require a much larger study. Although we assumed that wound complications may be harbingers for periprosthetic infections, no patient in either group developed periprosthetic infection. Therefore, we cannot conclude that surgical dressings play a role in reducing infections. In addition, as the standard dressing was changed on POD 2 (per standard protocol) and the occlusive dressing could remain in place for up to 7 days, there was a selection bias in the evaluation of the number of dressing changes. However, given the characteristics of the standard dressing (eg, tape, gauze, nonocclusive), leaving it in place after POD 2 is not optimal. Therefore, we would expect to see a difference in the number of dressing changes. We think this comparison remains valid, as occlusive dressings were changed when there were indications of wound problems (eg, excessive drainage [strike-through], surrounding erythema, blistering). With an average of less than 1 dressing change in the occlusive group, we think this is a surrogate for uneventful wound healing and decreased wound complication, and our data support this. It is also important to test both dressing durability and patient tolerance for wearing a single dressing for 7 days.

Our RCT results showed that, compared with a standard dressing, an occlusive antimicrobial dressing was associated with a significant decrease in overall wound complications and blisters. These findings are similar to those of other studies of occlusive dressings in a number of surgical subspecialties.^16,18 In an RCT of 200 patients who underwent elective and nonelective hip and knee surgery and were randomized to either absorbent perforated dressing with adhesive border (Cutiplast, Smith & Nephew) or Aquacel (ConvaTec) covered with vapor-permeable dressing (Tegaderm, 3M), Ravenscroft and colleagues²⁰ found that Aquacel-plus-Tegaderm was 5.8 times more likely than Cutiplast to produce an uncompromised wound. Similarly, in an RCT of hydrofiber (Aquacel) and central pad (Mepore, Mölnlycke) dressings after primary THA and TKA, Abuzakuk and colleagues¹⁹ found significantly fewer dressing changes (43% vs 77%) and blisters (13% vs 26%) in the hydrofiber group than in the pad group.

Hopper and colleagues²⁴ compared 50 consecutive patients treated with modern dressings (Aquacel) with 50 historical control patients treated with traditional surgical dressings (Mepore). Blisters developed in 20% of the patients in the traditional group and 4% of patients in the modern group (P = .028). The authors concluded that adverse outcomes of wound healing can be minimized with modern dressings.

A recent retrospective study by Cai and colleagues²⁵ evaluated the incidence of acute periprosthetic infection (≤3 months after surgery) with use of occlusive (Aquacel) and standard dressings. Incidence of acute periprosthetic infection was 0.44% in the occlusive group and 1.7% in the standard group (P = .005). Incidence of wound-healing problems was not evaluated.

Our second aim in the present study was to evaluate the number of dressing changes required. There were significantly fewer dressing changes in the occlusive dressing group than in the standard dressing group. Therefore, wear time (amount of time a single dressing remains in place) was substantially longer for the occlusive group. In the study by Hopper and colleagues,²⁴ wear time was significantly shorter for the traditional dressing than for the modern dressing (2 vs 7 days; P < .001), and the traditional dressing required more changes (3 vs 0; P < .001).

These findings are important for several reasons. Standard surgical dressings often require frequent changes. If left in place, they create an excessively moist wound environment that promotes blistering and delays wound healing. However, frequent dressing changes expose the wound and increase the risk for surgical site infection.²⁶ A barrier dressing left in place from time of surgery prevents bacteria from entering and contaminating a healing wound. A study by Clarke and colleagues²¹ demonstrated higher skin colonization rates for patients who had dressings changed on POD 1 than for patients who had their first dressing change on POD 6.

Our third study aim was to evaluate patient satisfaction with surgical dressings. The orthopedic literature has little on this topic.²³ Blisters and other wound complications can negatively affect satisfaction.^2,3 Our data showed significant improvement in satisfaction, particularly regarding sterility and hygiene.

Other surgical subspecialties have found similar improvement in patient satisfaction with occlusive barrier dressings. In an RCT of 88 pediatric patients, Rasmussen and colleagues²⁷ found that patients reported significantly less pain during changes of an occlusive adhesive dressing (Duoderm, ConvaTec) than during changes of a conventional Steristrip (3M) plus Cutiplast. According to the authors, the occlusive wound dressing seemed to minimize the physical and psychological trauma to the infant or child and lessen disruption of the child’s and the parents’ daily routines, because the children could be bathed immediately after surgery.

Our study did not specifically address cost. Cai and colleagues²⁵ estimated that, if the Aquacel dressing were routinely used in every hip and knee arthroplasty, it would add about $27 million in cost. However, this must be balanced by the cost of managing infection after TJA. In the United States, at an estimated $50,000 to $100,000 per case and an annual incidence of 1% to 2%, the low-end cost for the treatment of periprosthetic infection would be $500 million.²⁸ Cai and colleagues²⁵ found a 4-fold reduction in periprosthetic infection when use of occlusive dressings was implemented. In addition, wound complications remain the number one reason for hospital readmission after TJA.^12,13 Cost of hospital readmission, as well as financial penalties to institutions for unplanned readmission for wound complications, must be considered.

Conclusion

Our RCT results demonstrated that use of occlusive antimicrobial barrier dressings (vs standard surgical dressings) significantly reduced wound complications and dressing changes and improved overall patient satisfaction. These findings are similar to those in the literature on TJA and other surgical subspecialties. We conclude that occlusive surgical dressings reduce wound complications after TJA.

Femoral stem modularity in total hip arthroplasty (THA) has a checkered past. Developments such as the modular head–trunnion interface, which allows for placement of femoral heads of different sizes and offsets, and the modular midstem, which allows for version adjustments independent of patient anatomy (S-ROM, Depuy) and for bypassing proximal bone defects in the revision setting (Restoration Modular, Stryker; ZMR-XL, Zimmer), have proved very successful.^1-10 However, even these successful advances have been associated with failures at the modular junction.^11-13 Proximal femoral neck–stem modularity (PFNSM) has had mixed results, with notable failures and recalls associated with the neck–stem junction.^14,15 Failures at this junction have occurred secondary to corrosion and breakage of the modular neck.^16-18 Nevertheless, proximal modular stems remain available for implantation. One such system, the M/L Taper stem with Kinectiv technology (Zimmer), is an all-titanium construct that allows for adjustment of several variables (length, offset, version), providing numerous combinations beyond those of the original M/L Taper offerings. Advantages of these offerings include closer reconstruction of patient anatomy, stability improvements, and easing of the process of revision in polyethylene/femoral head exchanges or in infections in which single-staged irrigation and débridement and polyethylene/head exchange are chosen.

These theoretic advantages must be judged in the context of the possible disadvantages of the modular neck junction. The mechanical environment of the junction places it at risk for failure as well as for metallosis from fretting, crevice corrosion, and recurrent repassivation.¹⁹ Although the titanium necks are at less risk for degradation than their cobalt-chromium counterparts, they are at higher risk for breakage.^13,19 For one of the surgeons in our practice, the M/L Taper stem with Kinectiv technology is the stem of choice for primary THA.

We conducted a study to determine, in the setting of primary THA, how often a neck–stem combination choice resulted in a reconstructive geometry that would not have been possible had the surgeon opted for the traditional M/L Taper stem. Every Kinectiv stem has numerous neck options with a head center position that would not be possible with the nonmodular M/L Taper. However, in a high-volume community practice, how often is a modular neck that results in an otherwise unavailable head center being used for the reconstruction?

Materials and Methods

This study was approved by our local institutional review board. The Kinectiv stem is used by 1 of the 4 high-volume joint replacement surgeons in our practice (not one of the authors). From our community practice joint registry, we identified every stem–neck combination used since the Kinectiv stem became available in 2006.²⁰ Each case was performed using a posterior approach. A trabecular metal acetabular component (Zimmer) secured with 2 screws was used, and an M/L Taper stem with Kinectiv technology was implanted in each case.

Once the neck–stem combination was determined, its position on the head centers map was compared with that of the standard M/L Taper head centers (Figures 1, 2) for each stem size as the relationship of the Kinectiv head center varies with each stem size compared with the head center of the M/L Taper stems. If the head centers were in contact on the map, the geometry was considered identical. If the head centers were not in contact, we noted where the nearest standard M/L Taper head center lay in terms of length and offset. As the head centers are laid out in regular, 4-mm increments, this estimation was relatively easy. Any anteverted or retroverted neck was considered to have no adequate substitution in the standard M/L Taper stem offerings. This initial evaluation was performed by Dr. Carothers.

We then reviewed the head center comparisons independently. For every Kinectiv head center that did not contact an M/L Taper counterpart, the difference between those head centers was reviewed. Each of us noted whether the difference between the head centers was clinically relevant, as many of the head center positions are extremely close. The head centers that were so close as to be deemed clinically irrelevant were recorded.

Results

Between January 2008 and October 2013, 463 primary THAs were performed using the M/L Taper femoral stem with Kinectiv technology. Of the neck options used, 205 (44%) had a head center identical to that of a nonmodular M/L Taper stem. In another 56 cases (12%), all 3 reviewing surgeons agreed that the M/L Taper head center was so close to the Kinectiv head center as to be clinically indistinguishable. Of these 56 cases, 54 had a head center difference of less than 1 mm in length or offset; the other 2 had a 2-mm difference in offset.

Thus, a total of 261 stems (56%) had a standard M/L Taper option that offered an identical head center or one so close as to be clinically indistinguishable. Interestingly, in the group of 202 stems that did not have an identical head center and were not clinically indistinguishable, 132 (65%) of these modular stems were within 4 mm in length and 2 mm of offset of the closest Kinectiv head center. A verted neck was used in 12 cases (11 anteverted, 1 retroverted).

Nine of the 463 cases required revision surgery, 3 for recurrent instability. In 1 of these 3 cases, the acetabulum was revised for malposition, and the neck was converted from standard offset, +0 mm length (head center identical to nonmodular stem), to extended offset, +4 mm length (2 mm shorter with 1 mm less offset than closest nonmodular head center). The second case had complete deficiency of the abductor tendons and was converted to a constrained liner, though at the time of the THA a head center identical to that of the nonmodular stem was used. The third case was revised to convert a standard offset, +0 mm length, straight neck (head center identical to nonmodular stem), to extended offset, +4 mm length, anteverted neck (anteversion making this a unique head center position). Of the other 6 cases, 1 was treated for corrosion at the head–neck junction by changing the head from cobalt-chromium to ceramic (the junction was noted to be pristine), 1 underwent revision of the acetabular component for loosening, 2 femoral stems were revised for periprosthetic femur fracture, and 2 cases underwent 2-stage revision for late infection. There were no failures secondary to metallosis at the neck–stem junction and no modular breakages. The 3 cases of recurrent instability had no dislocation episodes after revision.

Discussion

PFNSM was developed to help more closely reconstruct patient anatomy. PFNSM allows for individualization of offset, length, and version—and thus for optimization of component interaction to avoid impingement and dislocation while promoting range of motion and normal gait.²¹ These benefits must be judged in light of the disadvantages of proximal stem modularity, including corrosion and breakage of the modular neck.^14-18

In the present study, conducted in a high-volume private practice setting, 44% of necks used in a proximally modular construct had a head center identical to that of a nonmodular alternative. In the opinion of the 3 authors (high-volume hip surgeons), an additional 12% of the modular stems had a head center so close to that of the nonmodular stem as to be clinically indistinguishable. In addition, 132 of the modular necks had a femoral head center within 4 mm in length and 2 mm of offset of the nonmodular stem. These findings call into question the theoretical benefits of regular use of this modular femoral stem for primary THA. Certainly there are extreme femoral neck–shaft angle cases in which the standard nonmodular stem may be inadequate and this proximal modularity would be helpful, but our study showed such cases are relatively less frequent. We caution against routine use of this proximal modularity in primary THA and suggest restricting it to cases in which the standard stem offerings are unacceptable. These findings are not surprising given that the standard M/L Taper stem is based on a historically successful model with neck angle and length options designed to meet the goals of restoring length, offset, range of motion, and stability. We would expect that a well-designed stem will meet these goals in the majority of cases.

Of our 463 cases with the modular neck, 9 required revision surgery. Of these 9 revisions, 2 were for recurrent dislocation in which the modular neck was revised to one that enhanced stability, and there were no further dislocations. The ability to change the geometry of the proximal femur resulted in a stability solution that avoided revision of the entire femoral component, as might otherwise be required. One case of acetabular loosening and 1 case that required placement of a constrained liner were potentially benefited by the modular neck in that the surgeries may have been expedited by being able to remove the neck to ease exposure for placement of the acetabular components. The other 5 revisions—2 for periprosthetic femur fracture, 2 two-stage revisions for infection, and 1 femoral head exchange for metallosis at the head–neck junction—saw no benefit from the modularity in the revision setting.

This study had several limitations. First, as it was primarily an evaluation of use of a modular femoral system, there was no attempt to account for the fact that acetabular component orientation can affect stability and, thus, the perceived need for additional offset or changes in version. The habit of all 3 of the reviewing surgeons is to consider the position of the acetabular component and to reposition the component, if necessary, to achieve appropriate stability. Therefore, the need for the modularity may be even less than suggested by this study. In addition, the idea that (in 12 cases) no standard stem option would be acceptable because of the use of a verted neck ignores the possibility that cup repositioning could have obviated the need for additional version. Furthermore, use of a 36-mm head results in an additional 3.5 mm of offset in the polyethylene liner, and this study did not account for the option of increasing head size—and for the potential increase in stability from a larger head and the increased offset gained from the liner.

A second limitation is that a significant number of Kinectiv stems (132) had a head center within 4 mm in length and 2 mm of offset of the nearest M/L Taper stem. We carefully template every primary THA to determine the plan that will optimize component size and position and restore length and offset. More options for achieving these goals are available when templating with the intention of using the Kinectiv modular neck. The neck cut and position of the stem proximally or distally in the proximal femur may not need to be so exact, as the additional options may be able to accommodate minor inaccuracies. Thus, the reported percentage of clinically indistinguishable head centers (12%) may underestimate the actual number of modular stems that could have been replaced with a nonmodular stem.

Third, this study did not evaluate the effect of the modular junction on ease of irrigation and débridement with head/neck and polyethylene exchange in cases of infection, or on ease of head/neck and polyethylene exchange for revision. In addition, the study did not evaluate other cases of instability involving a nonmodular stem that otherwise could have been solved with simple revision of the head/neck combination, avoiding revision of the entire stem and/or the acetabular component. We reported revisions for infection and for instability, but comprehensive assessment and comparison were beyond the scope of this study. Certainly ease of revision of the head and neck is a factor that could favor use of the modularity.

Fourth, this was not a clinical outcome study comparing 2 different femoral stems. We sought only to determine how often a modular neck was chosen that resulted in a head center that would have been unavailable to the non-modular stem suggesting that the patient was receiving a reconstructive benefit in exchange for the modularity. However, 2 recent reports have noted no clinical benefit at 2-year follow-up with use of the modular neck compared with the nonmodular stem.^22,23

Though the M/L Taper with Kinectiv technology has, thus far, performed well, PFNSM should be used with caution in light of recently reported failures at the neck–stem junction.14,16-18 Our study results suggest that most (≥56%) of the modular stems used could have been reconstructed as acceptably with a nonmodular stem, and therefore a reconstructive benefit was not realized in trade for the potential risks of proximal modularity. Only 2 of the 9 revision cases saw a clear advantage in being able to change the modular neck geometry in the revision setting. Given the recently reported failures and the high-profile recall of a modular stem,14 we recommend restricting the modular stem to cases that cannot be adequately reconstructed with the nonmodular option.

Femoral stem modularity in total hip arthroplasty (THA) has a checkered past. Developments such as the modular head–trunnion interface, which allows for placement of femoral heads of different sizes and offsets, and the modular midstem, which allows for version adjustments independent of patient anatomy (S-ROM, Depuy) and for bypassing proximal bone defects in the revision setting (Restoration Modular, Stryker; ZMR-XL, Zimmer), have proved very successful.^1-10 However, even these successful advances have been associated with failures at the modular junction.^11-13 Proximal femoral neck–stem modularity (PFNSM) has had mixed results, with notable failures and recalls associated with the neck–stem junction.^14,15 Failures at this junction have occurred secondary to corrosion and breakage of the modular neck.^16-18 Nevertheless, proximal modular stems remain available for implantation. One such system, the M/L Taper stem with Kinectiv technology (Zimmer), is an all-titanium construct that allows for adjustment of several variables (length, offset, version), providing numerous combinations beyond those of the original M/L Taper offerings. Advantages of these offerings include closer reconstruction of patient anatomy, stability improvements, and easing of the process of revision in polyethylene/femoral head exchanges or in infections in which single-staged irrigation and débridement and polyethylene/head exchange are chosen.

These theoretic advantages must be judged in the context of the possible disadvantages of the modular neck junction. The mechanical environment of the junction places it at risk for failure as well as for metallosis from fretting, crevice corrosion, and recurrent repassivation.¹⁹ Although the titanium necks are at less risk for degradation than their cobalt-chromium counterparts, they are at higher risk for breakage.^13,19 For one of the surgeons in our practice, the M/L Taper stem with Kinectiv technology is the stem of choice for primary THA.

We conducted a study to determine, in the setting of primary THA, how often a neck–stem combination choice resulted in a reconstructive geometry that would not have been possible had the surgeon opted for the traditional M/L Taper stem. Every Kinectiv stem has numerous neck options with a head center position that would not be possible with the nonmodular M/L Taper. However, in a high-volume community practice, how often is a modular neck that results in an otherwise unavailable head center being used for the reconstruction?

Materials and Methods

This study was approved by our local institutional review board. The Kinectiv stem is used by 1 of the 4 high-volume joint replacement surgeons in our practice (not one of the authors). From our community practice joint registry, we identified every stem–neck combination used since the Kinectiv stem became available in 2006.²⁰ Each case was performed using a posterior approach. A trabecular metal acetabular component (Zimmer) secured with 2 screws was used, and an M/L Taper stem with Kinectiv technology was implanted in each case.

Once the neck–stem combination was determined, its position on the head centers map was compared with that of the standard M/L Taper head centers (Figures 1, 2) for each stem size as the relationship of the Kinectiv head center varies with each stem size compared with the head center of the M/L Taper stems. If the head centers were in contact on the map, the geometry was considered identical. If the head centers were not in contact, we noted where the nearest standard M/L Taper head center lay in terms of length and offset. As the head centers are laid out in regular, 4-mm increments, this estimation was relatively easy. Any anteverted or retroverted neck was considered to have no adequate substitution in the standard M/L Taper stem offerings. This initial evaluation was performed by Dr. Carothers.

We then reviewed the head center comparisons independently. For every Kinectiv head center that did not contact an M/L Taper counterpart, the difference between those head centers was reviewed. Each of us noted whether the difference between the head centers was clinically relevant, as many of the head center positions are extremely close. The head centers that were so close as to be deemed clinically irrelevant were recorded.

Results

Between January 2008 and October 2013, 463 primary THAs were performed using the M/L Taper femoral stem with Kinectiv technology. Of the neck options used, 205 (44%) had a head center identical to that of a nonmodular M/L Taper stem. In another 56 cases (12%), all 3 reviewing surgeons agreed that the M/L Taper head center was so close to the Kinectiv head center as to be clinically indistinguishable. Of these 56 cases, 54 had a head center difference of less than 1 mm in length or offset; the other 2 had a 2-mm difference in offset.

Thus, a total of 261 stems (56%) had a standard M/L Taper option that offered an identical head center or one so close as to be clinically indistinguishable. Interestingly, in the group of 202 stems that did not have an identical head center and were not clinically indistinguishable, 132 (65%) of these modular stems were within 4 mm in length and 2 mm of offset of the closest Kinectiv head center. A verted neck was used in 12 cases (11 anteverted, 1 retroverted).

Nine of the 463 cases required revision surgery, 3 for recurrent instability. In 1 of these 3 cases, the acetabulum was revised for malposition, and the neck was converted from standard offset, +0 mm length (head center identical to nonmodular stem), to extended offset, +4 mm length (2 mm shorter with 1 mm less offset than closest nonmodular head center). The second case had complete deficiency of the abductor tendons and was converted to a constrained liner, though at the time of the THA a head center identical to that of the nonmodular stem was used. The third case was revised to convert a standard offset, +0 mm length, straight neck (head center identical to nonmodular stem), to extended offset, +4 mm length, anteverted neck (anteversion making this a unique head center position). Of the other 6 cases, 1 was treated for corrosion at the head–neck junction by changing the head from cobalt-chromium to ceramic (the junction was noted to be pristine), 1 underwent revision of the acetabular component for loosening, 2 femoral stems were revised for periprosthetic femur fracture, and 2 cases underwent 2-stage revision for late infection. There were no failures secondary to metallosis at the neck–stem junction and no modular breakages. The 3 cases of recurrent instability had no dislocation episodes after revision.

Discussion

PFNSM was developed to help more closely reconstruct patient anatomy. PFNSM allows for individualization of offset, length, and version—and thus for optimization of component interaction to avoid impingement and dislocation while promoting range of motion and normal gait.²¹ These benefits must be judged in light of the disadvantages of proximal stem modularity, including corrosion and breakage of the modular neck.^14-18

In the present study, conducted in a high-volume private practice setting, 44% of necks used in a proximally modular construct had a head center identical to that of a nonmodular alternative. In the opinion of the 3 authors (high-volume hip surgeons), an additional 12% of the modular stems had a head center so close to that of the nonmodular stem as to be clinically indistinguishable. In addition, 132 of the modular necks had a femoral head center within 4 mm in length and 2 mm of offset of the nonmodular stem. These findings call into question the theoretical benefits of regular use of this modular femoral stem for primary THA. Certainly there are extreme femoral neck–shaft angle cases in which the standard nonmodular stem may be inadequate and this proximal modularity would be helpful, but our study showed such cases are relatively less frequent. We caution against routine use of this proximal modularity in primary THA and suggest restricting it to cases in which the standard stem offerings are unacceptable. These findings are not surprising given that the standard M/L Taper stem is based on a historically successful model with neck angle and length options designed to meet the goals of restoring length, offset, range of motion, and stability. We would expect that a well-designed stem will meet these goals in the majority of cases.

Of our 463 cases with the modular neck, 9 required revision surgery. Of these 9 revisions, 2 were for recurrent dislocation in which the modular neck was revised to one that enhanced stability, and there were no further dislocations. The ability to change the geometry of the proximal femur resulted in a stability solution that avoided revision of the entire femoral component, as might otherwise be required. One case of acetabular loosening and 1 case that required placement of a constrained liner were potentially benefited by the modular neck in that the surgeries may have been expedited by being able to remove the neck to ease exposure for placement of the acetabular components. The other 5 revisions—2 for periprosthetic femur fracture, 2 two-stage revisions for infection, and 1 femoral head exchange for metallosis at the head–neck junction—saw no benefit from the modularity in the revision setting.

This study had several limitations. First, as it was primarily an evaluation of use of a modular femoral system, there was no attempt to account for the fact that acetabular component orientation can affect stability and, thus, the perceived need for additional offset or changes in version. The habit of all 3 of the reviewing surgeons is to consider the position of the acetabular component and to reposition the component, if necessary, to achieve appropriate stability. Therefore, the need for the modularity may be even less than suggested by this study. In addition, the idea that (in 12 cases) no standard stem option would be acceptable because of the use of a verted neck ignores the possibility that cup repositioning could have obviated the need for additional version. Furthermore, use of a 36-mm head results in an additional 3.5 mm of offset in the polyethylene liner, and this study did not account for the option of increasing head size—and for the potential increase in stability from a larger head and the increased offset gained from the liner.

A second limitation is that a significant number of Kinectiv stems (132) had a head center within 4 mm in length and 2 mm of offset of the nearest M/L Taper stem. We carefully template every primary THA to determine the plan that will optimize component size and position and restore length and offset. More options for achieving these goals are available when templating with the intention of using the Kinectiv modular neck. The neck cut and position of the stem proximally or distally in the proximal femur may not need to be so exact, as the additional options may be able to accommodate minor inaccuracies. Thus, the reported percentage of clinically indistinguishable head centers (12%) may underestimate the actual number of modular stems that could have been replaced with a nonmodular stem.

Third, this study did not evaluate the effect of the modular junction on ease of irrigation and débridement with head/neck and polyethylene exchange in cases of infection, or on ease of head/neck and polyethylene exchange for revision. In addition, the study did not evaluate other cases of instability involving a nonmodular stem that otherwise could have been solved with simple revision of the head/neck combination, avoiding revision of the entire stem and/or the acetabular component. We reported revisions for infection and for instability, but comprehensive assessment and comparison were beyond the scope of this study. Certainly ease of revision of the head and neck is a factor that could favor use of the modularity.

Fourth, this was not a clinical outcome study comparing 2 different femoral stems. We sought only to determine how often a modular neck was chosen that resulted in a head center that would have been unavailable to the non-modular stem suggesting that the patient was receiving a reconstructive benefit in exchange for the modularity. However, 2 recent reports have noted no clinical benefit at 2-year follow-up with use of the modular neck compared with the nonmodular stem.^22,23

Though the M/L Taper with Kinectiv technology has, thus far, performed well, PFNSM should be used with caution in light of recently reported failures at the neck–stem junction.14,16-18 Our study results suggest that most (≥56%) of the modular stems used could have been reconstructed as acceptably with a nonmodular stem, and therefore a reconstructive benefit was not realized in trade for the potential risks of proximal modularity. Only 2 of the 9 revision cases saw a clear advantage in being able to change the modular neck geometry in the revision setting. Given the recently reported failures and the high-profile recall of a modular stem,14 we recommend restricting the modular stem to cases that cannot be adequately reconstructed with the nonmodular option.

Femoral stem modularity in total hip arthroplasty (THA) has a checkered past. Developments such as the modular head–trunnion interface, which allows for placement of femoral heads of different sizes and offsets, and the modular midstem, which allows for version adjustments independent of patient anatomy (S-ROM, Depuy) and for bypassing proximal bone defects in the revision setting (Restoration Modular, Stryker; ZMR-XL, Zimmer), have proved very successful.^1-10 However, even these successful advances have been associated with failures at the modular junction.^11-13 Proximal femoral neck–stem modularity (PFNSM) has had mixed results, with notable failures and recalls associated with the neck–stem junction.^14,15 Failures at this junction have occurred secondary to corrosion and breakage of the modular neck.^16-18 Nevertheless, proximal modular stems remain available for implantation. One such system, the M/L Taper stem with Kinectiv technology (Zimmer), is an all-titanium construct that allows for adjustment of several variables (length, offset, version), providing numerous combinations beyond those of the original M/L Taper offerings. Advantages of these offerings include closer reconstruction of patient anatomy, stability improvements, and easing of the process of revision in polyethylene/femoral head exchanges or in infections in which single-staged irrigation and débridement and polyethylene/head exchange are chosen.

These theoretic advantages must be judged in the context of the possible disadvantages of the modular neck junction. The mechanical environment of the junction places it at risk for failure as well as for metallosis from fretting, crevice corrosion, and recurrent repassivation.¹⁹ Although the titanium necks are at less risk for degradation than their cobalt-chromium counterparts, they are at higher risk for breakage.^13,19 For one of the surgeons in our practice, the M/L Taper stem with Kinectiv technology is the stem of choice for primary THA.

We conducted a study to determine, in the setting of primary THA, how often a neck–stem combination choice resulted in a reconstructive geometry that would not have been possible had the surgeon opted for the traditional M/L Taper stem. Every Kinectiv stem has numerous neck options with a head center position that would not be possible with the nonmodular M/L Taper. However, in a high-volume community practice, how often is a modular neck that results in an otherwise unavailable head center being used for the reconstruction?

Materials and Methods

This study was approved by our local institutional review board. The Kinectiv stem is used by 1 of the 4 high-volume joint replacement surgeons in our practice (not one of the authors). From our community practice joint registry, we identified every stem–neck combination used since the Kinectiv stem became available in 2006.²⁰ Each case was performed using a posterior approach. A trabecular metal acetabular component (Zimmer) secured with 2 screws was used, and an M/L Taper stem with Kinectiv technology was implanted in each case.

Once the neck–stem combination was determined, its position on the head centers map was compared with that of the standard M/L Taper head centers (Figures 1, 2) for each stem size as the relationship of the Kinectiv head center varies with each stem size compared with the head center of the M/L Taper stems. If the head centers were in contact on the map, the geometry was considered identical. If the head centers were not in contact, we noted where the nearest standard M/L Taper head center lay in terms of length and offset. As the head centers are laid out in regular, 4-mm increments, this estimation was relatively easy. Any anteverted or retroverted neck was considered to have no adequate substitution in the standard M/L Taper stem offerings. This initial evaluation was performed by Dr. Carothers.

We then reviewed the head center comparisons independently. For every Kinectiv head center that did not contact an M/L Taper counterpart, the difference between those head centers was reviewed. Each of us noted whether the difference between the head centers was clinically relevant, as many of the head center positions are extremely close. The head centers that were so close as to be deemed clinically irrelevant were recorded.

Results

Between January 2008 and October 2013, 463 primary THAs were performed using the M/L Taper femoral stem with Kinectiv technology. Of the neck options used, 205 (44%) had a head center identical to that of a nonmodular M/L Taper stem. In another 56 cases (12%), all 3 reviewing surgeons agreed that the M/L Taper head center was so close to the Kinectiv head center as to be clinically indistinguishable. Of these 56 cases, 54 had a head center difference of less than 1 mm in length or offset; the other 2 had a 2-mm difference in offset.

Thus, a total of 261 stems (56%) had a standard M/L Taper option that offered an identical head center or one so close as to be clinically indistinguishable. Interestingly, in the group of 202 stems that did not have an identical head center and were not clinically indistinguishable, 132 (65%) of these modular stems were within 4 mm in length and 2 mm of offset of the closest Kinectiv head center. A verted neck was used in 12 cases (11 anteverted, 1 retroverted).

Nine of the 463 cases required revision surgery, 3 for recurrent instability. In 1 of these 3 cases, the acetabulum was revised for malposition, and the neck was converted from standard offset, +0 mm length (head center identical to nonmodular stem), to extended offset, +4 mm length (2 mm shorter with 1 mm less offset than closest nonmodular head center). The second case had complete deficiency of the abductor tendons and was converted to a constrained liner, though at the time of the THA a head center identical to that of the nonmodular stem was used. The third case was revised to convert a standard offset, +0 mm length, straight neck (head center identical to nonmodular stem), to extended offset, +4 mm length, anteverted neck (anteversion making this a unique head center position). Of the other 6 cases, 1 was treated for corrosion at the head–neck junction by changing the head from cobalt-chromium to ceramic (the junction was noted to be pristine), 1 underwent revision of the acetabular component for loosening, 2 femoral stems were revised for periprosthetic femur fracture, and 2 cases underwent 2-stage revision for late infection. There were no failures secondary to metallosis at the neck–stem junction and no modular breakages. The 3 cases of recurrent instability had no dislocation episodes after revision.

Discussion

PFNSM was developed to help more closely reconstruct patient anatomy. PFNSM allows for individualization of offset, length, and version—and thus for optimization of component interaction to avoid impingement and dislocation while promoting range of motion and normal gait.²¹ These benefits must be judged in light of the disadvantages of proximal stem modularity, including corrosion and breakage of the modular neck.^14-18

In the present study, conducted in a high-volume private practice setting, 44% of necks used in a proximally modular construct had a head center identical to that of a nonmodular alternative. In the opinion of the 3 authors (high-volume hip surgeons), an additional 12% of the modular stems had a head center so close to that of the nonmodular stem as to be clinically indistinguishable. In addition, 132 of the modular necks had a femoral head center within 4 mm in length and 2 mm of offset of the nonmodular stem. These findings call into question the theoretical benefits of regular use of this modular femoral stem for primary THA. Certainly there are extreme femoral neck–shaft angle cases in which the standard nonmodular stem may be inadequate and this proximal modularity would be helpful, but our study showed such cases are relatively less frequent. We caution against routine use of this proximal modularity in primary THA and suggest restricting it to cases in which the standard stem offerings are unacceptable. These findings are not surprising given that the standard M/L Taper stem is based on a historically successful model with neck angle and length options designed to meet the goals of restoring length, offset, range of motion, and stability. We would expect that a well-designed stem will meet these goals in the majority of cases.

Of our 463 cases with the modular neck, 9 required revision surgery. Of these 9 revisions, 2 were for recurrent dislocation in which the modular neck was revised to one that enhanced stability, and there were no further dislocations. The ability to change the geometry of the proximal femur resulted in a stability solution that avoided revision of the entire femoral component, as might otherwise be required. One case of acetabular loosening and 1 case that required placement of a constrained liner were potentially benefited by the modular neck in that the surgeries may have been expedited by being able to remove the neck to ease exposure for placement of the acetabular components. The other 5 revisions—2 for periprosthetic femur fracture, 2 two-stage revisions for infection, and 1 femoral head exchange for metallosis at the head–neck junction—saw no benefit from the modularity in the revision setting.

This study had several limitations. First, as it was primarily an evaluation of use of a modular femoral system, there was no attempt to account for the fact that acetabular component orientation can affect stability and, thus, the perceived need for additional offset or changes in version. The habit of all 3 of the reviewing surgeons is to consider the position of the acetabular component and to reposition the component, if necessary, to achieve appropriate stability. Therefore, the need for the modularity may be even less than suggested by this study. In addition, the idea that (in 12 cases) no standard stem option would be acceptable because of the use of a verted neck ignores the possibility that cup repositioning could have obviated the need for additional version. Furthermore, use of a 36-mm head results in an additional 3.5 mm of offset in the polyethylene liner, and this study did not account for the option of increasing head size—and for the potential increase in stability from a larger head and the increased offset gained from the liner.

A second limitation is that a significant number of Kinectiv stems (132) had a head center within 4 mm in length and 2 mm of offset of the nearest M/L Taper stem. We carefully template every primary THA to determine the plan that will optimize component size and position and restore length and offset. More options for achieving these goals are available when templating with the intention of using the Kinectiv modular neck. The neck cut and position of the stem proximally or distally in the proximal femur may not need to be so exact, as the additional options may be able to accommodate minor inaccuracies. Thus, the reported percentage of clinically indistinguishable head centers (12%) may underestimate the actual number of modular stems that could have been replaced with a nonmodular stem.

Third, this study did not evaluate the effect of the modular junction on ease of irrigation and débridement with head/neck and polyethylene exchange in cases of infection, or on ease of head/neck and polyethylene exchange for revision. In addition, the study did not evaluate other cases of instability involving a nonmodular stem that otherwise could have been solved with simple revision of the head/neck combination, avoiding revision of the entire stem and/or the acetabular component. We reported revisions for infection and for instability, but comprehensive assessment and comparison were beyond the scope of this study. Certainly ease of revision of the head and neck is a factor that could favor use of the modularity.

Fourth, this was not a clinical outcome study comparing 2 different femoral stems. We sought only to determine how often a modular neck was chosen that resulted in a head center that would have been unavailable to the non-modular stem suggesting that the patient was receiving a reconstructive benefit in exchange for the modularity. However, 2 recent reports have noted no clinical benefit at 2-year follow-up with use of the modular neck compared with the nonmodular stem.^22,23

Though the M/L Taper with Kinectiv technology has, thus far, performed well, PFNSM should be used with caution in light of recently reported failures at the neck–stem junction.14,16-18 Our study results suggest that most (≥56%) of the modular stems used could have been reconstructed as acceptably with a nonmodular stem, and therefore a reconstructive benefit was not realized in trade for the potential risks of proximal modularity. Only 2 of the 9 revision cases saw a clear advantage in being able to change the modular neck geometry in the revision setting. Given the recently reported failures and the high-profile recall of a modular stem,14 we recommend restricting the modular stem to cases that cannot be adequately reconstructed with the nonmodular option.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15 CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.

Results

Overall, 393 patients underwent revision arthroplasty for the diagnoses (ICD-9 codes) indicated (Figure). One hundred eighty-nine patients (48.1%) had CT performed before revision. Of these 189 patients, 85 were excluded for diagnoses that were evident on either plain radiography or CT, that necessitated urgent revision, or for procedures beyond the scope of the study (Table 1). CT showed a loose cup in 28 patients; 6 of these cups were also seen on CT. Thirteen patients were diagnosed with a loose femoral stem, 10 with a periprosthetic infection, and 8 with a periprosthetic fracture.

One hundred four patients (54 men, 50 women) met the study inclusion criteria. Mean age was 65.1 years. Of these 104 patients, 87 (83.7%) had a stable acetabular shell at time of revision surgery; the other 17 (16.3%) were diagnosed with RSL of the acetabular shell. Osteolysis was the most common diagnosis (89.4%) in the overall population, and pain was the most common complaint at time of presentation (66.6%). Lack of symptoms was the second most common presentation at time of revision (19.2%) (Table 2). Patients without symptoms underwent revision surgery because of concern about impending compromise of the bone–implant interface and progressive osteolysis.

The 2 groups (stable vs unstable acetabular shells) were not significantly different with respect to age (P = .961) or sex distribution (P = .185). All patients in the RSL group were diagnosed with osteolysis radiographically, and 15 (88%) of 17 patients presented with pain as the primary complaint, compared with only 54 (62%) of 87 patients in the group with stable shells. Patients with RSL were significantly more likely to present with pain as the primary complaint (P = .0487). Nineteen patients in the stable implant group and only 1 patient in the RSL group were asymptomatic, but this was not statistically significant (P = .185) when compared against all other diagnoses.

Discussion

We defined RSL as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Patients with RSL and the surgeons who treat them are in a difficult position. In the setting of osteolysis, patients can be treated with serial radiographic imaging and clinical monitoring to determine if and when revision arthroplasty should be performed.¹⁷ However, given the complexity and risks associated with revision THA, surgeons should be aware that the acetabular shell may necessitate revision even if it does not appear to be frankly unstable on radiographic imaging.¹⁸

Of the 393 patients who underwent revision THA at our institution, 48.1% were evaluated with CT. Eighty-five of the 189 patients who underwent CT were diagnosed with radiographic loosening, or were diagnosed as needing urgent revision THA in the setting of loose components, periprosthetic infection, periprosthetic fracture, or catastrophic implant failure. Of the remaining 104 patients, 17 (16.3%) met the diagnosis of RSL of the acetabular component. The most common complaint was pain, and the most common diagnoses were osteolysis and polyethylene wear. Age and sex were not associated with increased likelihood of RSL.

Our study has several limitations. We defined the radiographic diagnosis of loose acetabular components as components showing frank migration, tilting, or a 2-mm concentric lucency on plain radiography or CT. Although these are common definitions of loose acetabular components, more sensitive radiographic measures have been described.¹⁶ We also excluded patients with recurrent dislocations and metal-on-metal prostheses, as these cases increase the metal artifact on CT and limit the ability to evaluate the bone–implant interface. Metal artifact remains an ongoing challenge to use of CT for post-THA imaging. However, tailored imaging protocols are helping to eliminate metal artifact. Bone scan was not used to evaluate for possible component loosening. Although sensitivity and specificity are about 67% and 76%, respectively,²⁰ Temmerman and colleagues²¹ also found poor intraobserver reliability (0.53) for bone scans in the setting of uncemented acetabular components. Last, our study did not evaluate the bony ingrowth patterns that corresponded to stable or unstable fixation and did not evaluate the volumetric size or anatomical location of the osteolytic lesions on CT. Careful assessment of these variables is clinically relevant when trying to determine if revision arthroplasty is warranted.

Although we used relatively simple radiographic criteria to define loose components, more sensitive and specific techniques have been described for both plain radiography and CT. Moore and colleagues²² described 5 radiographic signs of bony ingrowth; when 3 or more were present, sensitivity was 89.6% and specificity 76.9%. Mehin and colleagues²³ suggested that osteolysis involving more than 50% of the circumference of the shell on a standard pelvic radiograph might require revision arthroplasty. However, more recent studies have found that anteroposterior and lateral radiographs are less able to evaluate the anterior and posterior rims of the bone–implant interface, and it is this ingrowth area that may be the most crucial for stable osseointegration.^12,16

CT has expanded our ability to evaluate the bone–implant interface in 3 dimensions. Egawa and colleagues¹⁶ described using CT to evaluate the surface area involved with osteolysis and found that less than 40% involvement of the surface area generally corresponded to well-fixed components. Furthermore, they found that osteolysis generally creates lesions inferior and superior to the acetabular component and less often involves the anterior and posterior rims, which may be more important for stable fixation. The authors noted that volumetric analysis and CT were not as cost-effective as plain radiography and were more time- and skill-intensive.

Osteolysis itself remains a common indication for revision THA. However, the most appropriate procedure remains controversial. Mallory and colleagues²⁴ recommended explanting all acetabular shells in the setting of revision arthroplasty. They indicated that full assessment of the bony pelvis and any lytic defects was possible only with the wide exposure gained by acetabular component removal. More recent studies have begun to justify isolated component revision in the setting of well-fixed acetabular shells. Studies by Maloney and colleagues,¹⁰ Park and colleagues,¹⁵ and Beaulé and colleagues²⁵ have shown excellent outcomes with retention of well-fixed acetabular shells and removal of the wear generator in the setting of osteolysis. Haidukewych¹⁷ wrote that the goals in addressing osteolysis in revision THA are to eliminate the wear generator, débride osteolytic lesions, and restore bone stock. Surgeons should weigh the benefits of component retention and isolated liner exchange against the morbidity associated with explantation and preparation for implanting a new component. Good outcomes have been achieved with isolated component exchange, but surgeons should be aware that instability remains the most common complication after isolated liner exchange.⁸

The majority of our patients with RSL presented with complaints of pain and the diagnosis of osteolysis. One patient who had the diagnosis but was clinically asymptomatic was found to have a loose acetabular shell at time of revision surgery. Given the increased morbidity associated with acetabular component revision, this patient’s condition represents a dangerous combination of RSL and clinically asymptomatic component loosening. By raising awareness about RSL and its incidence, we should be able to increase our ability to detect RSL. A surgeon who detects RSL before gross migration or movement of the acetabular component may be better able to plan for revision arthroplasty before a catastrophic event that may necessitate a larger, more complex procedure. With the number of patients who require revision THA continuing to rise, surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15 CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.

Results

Overall, 393 patients underwent revision arthroplasty for the diagnoses (ICD-9 codes) indicated (Figure). One hundred eighty-nine patients (48.1%) had CT performed before revision. Of these 189 patients, 85 were excluded for diagnoses that were evident on either plain radiography or CT, that necessitated urgent revision, or for procedures beyond the scope of the study (Table 1). CT showed a loose cup in 28 patients; 6 of these cups were also seen on CT. Thirteen patients were diagnosed with a loose femoral stem, 10 with a periprosthetic infection, and 8 with a periprosthetic fracture.

One hundred four patients (54 men, 50 women) met the study inclusion criteria. Mean age was 65.1 years. Of these 104 patients, 87 (83.7%) had a stable acetabular shell at time of revision surgery; the other 17 (16.3%) were diagnosed with RSL of the acetabular shell. Osteolysis was the most common diagnosis (89.4%) in the overall population, and pain was the most common complaint at time of presentation (66.6%). Lack of symptoms was the second most common presentation at time of revision (19.2%) (Table 2). Patients without symptoms underwent revision surgery because of concern about impending compromise of the bone–implant interface and progressive osteolysis.

The 2 groups (stable vs unstable acetabular shells) were not significantly different with respect to age (P = .961) or sex distribution (P = .185). All patients in the RSL group were diagnosed with osteolysis radiographically, and 15 (88%) of 17 patients presented with pain as the primary complaint, compared with only 54 (62%) of 87 patients in the group with stable shells. Patients with RSL were significantly more likely to present with pain as the primary complaint (P = .0487). Nineteen patients in the stable implant group and only 1 patient in the RSL group were asymptomatic, but this was not statistically significant (P = .185) when compared against all other diagnoses.

Discussion

We defined RSL as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Patients with RSL and the surgeons who treat them are in a difficult position. In the setting of osteolysis, patients can be treated with serial radiographic imaging and clinical monitoring to determine if and when revision arthroplasty should be performed.¹⁷ However, given the complexity and risks associated with revision THA, surgeons should be aware that the acetabular shell may necessitate revision even if it does not appear to be frankly unstable on radiographic imaging.¹⁸

Of the 393 patients who underwent revision THA at our institution, 48.1% were evaluated with CT. Eighty-five of the 189 patients who underwent CT were diagnosed with radiographic loosening, or were diagnosed as needing urgent revision THA in the setting of loose components, periprosthetic infection, periprosthetic fracture, or catastrophic implant failure. Of the remaining 104 patients, 17 (16.3%) met the diagnosis of RSL of the acetabular component. The most common complaint was pain, and the most common diagnoses were osteolysis and polyethylene wear. Age and sex were not associated with increased likelihood of RSL.

Our study has several limitations. We defined the radiographic diagnosis of loose acetabular components as components showing frank migration, tilting, or a 2-mm concentric lucency on plain radiography or CT. Although these are common definitions of loose acetabular components, more sensitive radiographic measures have been described.¹⁶ We also excluded patients with recurrent dislocations and metal-on-metal prostheses, as these cases increase the metal artifact on CT and limit the ability to evaluate the bone–implant interface. Metal artifact remains an ongoing challenge to use of CT for post-THA imaging. However, tailored imaging protocols are helping to eliminate metal artifact. Bone scan was not used to evaluate for possible component loosening. Although sensitivity and specificity are about 67% and 76%, respectively,²⁰ Temmerman and colleagues²¹ also found poor intraobserver reliability (0.53) for bone scans in the setting of uncemented acetabular components. Last, our study did not evaluate the bony ingrowth patterns that corresponded to stable or unstable fixation and did not evaluate the volumetric size or anatomical location of the osteolytic lesions on CT. Careful assessment of these variables is clinically relevant when trying to determine if revision arthroplasty is warranted.

Although we used relatively simple radiographic criteria to define loose components, more sensitive and specific techniques have been described for both plain radiography and CT. Moore and colleagues²² described 5 radiographic signs of bony ingrowth; when 3 or more were present, sensitivity was 89.6% and specificity 76.9%. Mehin and colleagues²³ suggested that osteolysis involving more than 50% of the circumference of the shell on a standard pelvic radiograph might require revision arthroplasty. However, more recent studies have found that anteroposterior and lateral radiographs are less able to evaluate the anterior and posterior rims of the bone–implant interface, and it is this ingrowth area that may be the most crucial for stable osseointegration.^12,16

CT has expanded our ability to evaluate the bone–implant interface in 3 dimensions. Egawa and colleagues¹⁶ described using CT to evaluate the surface area involved with osteolysis and found that less than 40% involvement of the surface area generally corresponded to well-fixed components. Furthermore, they found that osteolysis generally creates lesions inferior and superior to the acetabular component and less often involves the anterior and posterior rims, which may be more important for stable fixation. The authors noted that volumetric analysis and CT were not as cost-effective as plain radiography and were more time- and skill-intensive.

Osteolysis itself remains a common indication for revision THA. However, the most appropriate procedure remains controversial. Mallory and colleagues²⁴ recommended explanting all acetabular shells in the setting of revision arthroplasty. They indicated that full assessment of the bony pelvis and any lytic defects was possible only with the wide exposure gained by acetabular component removal. More recent studies have begun to justify isolated component revision in the setting of well-fixed acetabular shells. Studies by Maloney and colleagues,¹⁰ Park and colleagues,¹⁵ and Beaulé and colleagues²⁵ have shown excellent outcomes with retention of well-fixed acetabular shells and removal of the wear generator in the setting of osteolysis. Haidukewych¹⁷ wrote that the goals in addressing osteolysis in revision THA are to eliminate the wear generator, débride osteolytic lesions, and restore bone stock. Surgeons should weigh the benefits of component retention and isolated liner exchange against the morbidity associated with explantation and preparation for implanting a new component. Good outcomes have been achieved with isolated component exchange, but surgeons should be aware that instability remains the most common complication after isolated liner exchange.⁸

The majority of our patients with RSL presented with complaints of pain and the diagnosis of osteolysis. One patient who had the diagnosis but was clinically asymptomatic was found to have a loose acetabular shell at time of revision surgery. Given the increased morbidity associated with acetabular component revision, this patient’s condition represents a dangerous combination of RSL and clinically asymptomatic component loosening. By raising awareness about RSL and its incidence, we should be able to increase our ability to detect RSL. A surgeon who detects RSL before gross migration or movement of the acetabular component may be better able to plan for revision arthroplasty before a catastrophic event that may necessitate a larger, more complex procedure. With the number of patients who require revision THA continuing to rise, surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15 CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.

Results

Overall, 393 patients underwent revision arthroplasty for the diagnoses (ICD-9 codes) indicated (Figure). One hundred eighty-nine patients (48.1%) had CT performed before revision. Of these 189 patients, 85 were excluded for diagnoses that were evident on either plain radiography or CT, that necessitated urgent revision, or for procedures beyond the scope of the study (Table 1). CT showed a loose cup in 28 patients; 6 of these cups were also seen on CT. Thirteen patients were diagnosed with a loose femoral stem, 10 with a periprosthetic infection, and 8 with a periprosthetic fracture.

One hundred four patients (54 men, 50 women) met the study inclusion criteria. Mean age was 65.1 years. Of these 104 patients, 87 (83.7%) had a stable acetabular shell at time of revision surgery; the other 17 (16.3%) were diagnosed with RSL of the acetabular shell. Osteolysis was the most common diagnosis (89.4%) in the overall population, and pain was the most common complaint at time of presentation (66.6%). Lack of symptoms was the second most common presentation at time of revision (19.2%) (Table 2). Patients without symptoms underwent revision surgery because of concern about impending compromise of the bone–implant interface and progressive osteolysis.

The 2 groups (stable vs unstable acetabular shells) were not significantly different with respect to age (P = .961) or sex distribution (P = .185). All patients in the RSL group were diagnosed with osteolysis radiographically, and 15 (88%) of 17 patients presented with pain as the primary complaint, compared with only 54 (62%) of 87 patients in the group with stable shells. Patients with RSL were significantly more likely to present with pain as the primary complaint (P = .0487). Nineteen patients in the stable implant group and only 1 patient in the RSL group were asymptomatic, but this was not statistically significant (P = .185) when compared against all other diagnoses.

Discussion

We defined RSL as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Patients with RSL and the surgeons who treat them are in a difficult position. In the setting of osteolysis, patients can be treated with serial radiographic imaging and clinical monitoring to determine if and when revision arthroplasty should be performed.¹⁷ However, given the complexity and risks associated with revision THA, surgeons should be aware that the acetabular shell may necessitate revision even if it does not appear to be frankly unstable on radiographic imaging.¹⁸

Of the 393 patients who underwent revision THA at our institution, 48.1% were evaluated with CT. Eighty-five of the 189 patients who underwent CT were diagnosed with radiographic loosening, or were diagnosed as needing urgent revision THA in the setting of loose components, periprosthetic infection, periprosthetic fracture, or catastrophic implant failure. Of the remaining 104 patients, 17 (16.3%) met the diagnosis of RSL of the acetabular component. The most common complaint was pain, and the most common diagnoses were osteolysis and polyethylene wear. Age and sex were not associated with increased likelihood of RSL.

Our study has several limitations. We defined the radiographic diagnosis of loose acetabular components as components showing frank migration, tilting, or a 2-mm concentric lucency on plain radiography or CT. Although these are common definitions of loose acetabular components, more sensitive radiographic measures have been described.¹⁶ We also excluded patients with recurrent dislocations and metal-on-metal prostheses, as these cases increase the metal artifact on CT and limit the ability to evaluate the bone–implant interface. Metal artifact remains an ongoing challenge to use of CT for post-THA imaging. However, tailored imaging protocols are helping to eliminate metal artifact. Bone scan was not used to evaluate for possible component loosening. Although sensitivity and specificity are about 67% and 76%, respectively,²⁰ Temmerman and colleagues²¹ also found poor intraobserver reliability (0.53) for bone scans in the setting of uncemented acetabular components. Last, our study did not evaluate the bony ingrowth patterns that corresponded to stable or unstable fixation and did not evaluate the volumetric size or anatomical location of the osteolytic lesions on CT. Careful assessment of these variables is clinically relevant when trying to determine if revision arthroplasty is warranted.

Although we used relatively simple radiographic criteria to define loose components, more sensitive and specific techniques have been described for both plain radiography and CT. Moore and colleagues²² described 5 radiographic signs of bony ingrowth; when 3 or more were present, sensitivity was 89.6% and specificity 76.9%. Mehin and colleagues²³ suggested that osteolysis involving more than 50% of the circumference of the shell on a standard pelvic radiograph might require revision arthroplasty. However, more recent studies have found that anteroposterior and lateral radiographs are less able to evaluate the anterior and posterior rims of the bone–implant interface, and it is this ingrowth area that may be the most crucial for stable osseointegration.^12,16

CT has expanded our ability to evaluate the bone–implant interface in 3 dimensions. Egawa and colleagues¹⁶ described using CT to evaluate the surface area involved with osteolysis and found that less than 40% involvement of the surface area generally corresponded to well-fixed components. Furthermore, they found that osteolysis generally creates lesions inferior and superior to the acetabular component and less often involves the anterior and posterior rims, which may be more important for stable fixation. The authors noted that volumetric analysis and CT were not as cost-effective as plain radiography and were more time- and skill-intensive.

Osteolysis itself remains a common indication for revision THA. However, the most appropriate procedure remains controversial. Mallory and colleagues²⁴ recommended explanting all acetabular shells in the setting of revision arthroplasty. They indicated that full assessment of the bony pelvis and any lytic defects was possible only with the wide exposure gained by acetabular component removal. More recent studies have begun to justify isolated component revision in the setting of well-fixed acetabular shells. Studies by Maloney and colleagues,¹⁰ Park and colleagues,¹⁵ and Beaulé and colleagues²⁵ have shown excellent outcomes with retention of well-fixed acetabular shells and removal of the wear generator in the setting of osteolysis. Haidukewych¹⁷ wrote that the goals in addressing osteolysis in revision THA are to eliminate the wear generator, débride osteolytic lesions, and restore bone stock. Surgeons should weigh the benefits of component retention and isolated liner exchange against the morbidity associated with explantation and preparation for implanting a new component. Good outcomes have been achieved with isolated component exchange, but surgeons should be aware that instability remains the most common complication after isolated liner exchange.⁸

The majority of our patients with RSL presented with complaints of pain and the diagnosis of osteolysis. One patient who had the diagnosis but was clinically asymptomatic was found to have a loose acetabular shell at time of revision surgery. Given the increased morbidity associated with acetabular component revision, this patient’s condition represents a dangerous combination of RSL and clinically asymptomatic component loosening. By raising awareness about RSL and its incidence, we should be able to increase our ability to detect RSL. A surgeon who detects RSL before gross migration or movement of the acetabular component may be better able to plan for revision arthroplasty before a catastrophic event that may necessitate a larger, more complex procedure. With the number of patients who require revision THA continuing to rise, surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.

Total joint arthroplasty (TJA) is a clinically effective, cost-effective treatment for symptomatic arthritis.^1,2 After TJA, patients report reduced pain, restored range of motion, high satisfaction, and ability to return to a more active lifestyle.^3-7 The number of total hip arthroplasties (THAs) performed in the United States is expected to reach 572,000 by 2030, a 174% increase, and the number of total knee arthroplasties (TKAs) 3.5 million, nearly a 7-fold increase.^8,9 Since 2005, the cost of THA has risen more than 4 times, to $13.43 billion, and the cost of TKA has risen more than 5 times, to $40.8 billion.^8,9 Given the demand and price tag, TJA is the single largest cost in the Medicare budget.¹⁰

Given its potential to improve care and reduce costs, reducing readmission rates in the surgical setting is a priority for physicians and policymakers.¹¹ Readmissions for TJA are highly scrutinized as a performance indicator—the Centers for Medicare & Medicaid Services (CMS) started including them in its readmissions penalty program in 2013—and were recently validated as a measure of surgical quality.^12-14 Accurate assessments of readmissions after TJA are unclear, with rates ranging from 1% to 8.5% between 7 and 90 days after surgery.^2,15-17 The early success of TJA as an elective (and more frequently outpatient) procedure has paradoxically translated to less tolerance for readmissions. Post-TJA complications resulting in readmission are subject to financial penalties, and there is an implicit judgment of inadequate surgical management.¹²

Not only is the readmission rate poorly characterized, but there is no consensus on the leading reasons for readmissions after primary elective unilateral TJAs. The range of rates, reasons, and follow-up periods reported in the literature is wide.^18,19 CMS plans to monitor readmissions over 7 to 90 days after surgery (the period depends on the complication), whereas a significant portion of the orthopedic literature documents 90-day rates.¹⁹ In 2012, the Yale New Haven Health Services Corporation/Center for Outcomes Research and Evaluation prepared for CMS a comprehensive report identifying rates of post-TJA complications and readmissions.²⁰ The report, however, is limited to US hospitals and Medicare patients and therefore may overstate the rates, given this population’s documented comorbidities and the reimbursement variations between Medicare and commercial insurance.²¹ Lack of consensus on readmissions after primary elective unilateral TJAs requires that we synthesize available data to answer several questions: What is the overall readmission rate 30 and 90 days after TJA? What are the primary reasons for readmission 30 and 90 days after TJA? What are the cause-specific readmission rates? We performed a systematic review and a meta-analysis to answer these questions and to add clarity to the literature in order to help guide policy.

Materials and Methods

We performed a systematic review in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.²² Two reviewers independently completed structured searches of the Medline and Cochrane Central Register of Controlled Trials databases. Search terms were: (total hip replacement OR hip arthroplasty OR total hip arthroplasty OR total knee replacement OR knee arthroplasty OR total knee arthroplasty) AND (readmission OR complication OR discharge). They updated the search June 1, 2013. Four limits were applied: publication between January 1, 1982 and December 12, 2012; human subjects only; age 19+ years; and English-language articles. Study eligibility was determined by using standardized criteria as defined by the inclusion and exclusion criteria described in 3 stages: title review, abstract review, and full-article review. The reviewers also performed ancestry searches, including searches for major review articles and bibliographies of all retrieved studies, to identify additional studies not identified in the keyword searches. Discrepancies were resolved by author consensus.

Inclusion criteria were original studies that presented level I to III evidence and that were identified in structured online searches; published in English between January 1, 1982 and December 31, 2012; involved patients older than 19 years; and reported both readmission rates and reasons at follow-up 30 or 90 days after elective primary unilateral TJA, regardless of indication. Exclusion criteria were studies that reported data from hip fracture, knee fracture, and pelvis fracture cases; those that reported data from hemiarthroplasty, Birmingham hip resurfacing procedures, other resurfacing procedures, simultaneous bilateral hip or knee arthroplasties, unicompartmental knee arthroplasty, patellofemoral arthroplasty, metastatic or bone cancer, or revision hip or knee arthroplasty; those that did not report extractable reasons for readmission; those that reported complications but did not specify readmission rates; and those that reported readmission data only from after the 90-day follow-up window. In cases in which multiple studies reported data from the same patient population, only the largest or most recent report was used.

Two reviewers extracted the quantitative data from eligible studies. The 2 primary outcomes of interests were all-cause readmission rates, and reasons for readmission 30 and 90 days after TJA. Other extracted data were evidence level; publication journal, year, and country; data source (academic institution, Medicare); study design; number of patients; patient characteristics; surgical approach; follow-up period; overall readmission rate; anticoagulant use; tourniquet use; and compression stocking use. In addition, all post-TJA readmissions were assumed to be unplanned, except for staged sequential bilateral arthroplasty for osteoarthritis (excluded from analysis).

Readmission reasons were divided into 4 major categories as defined by the literature and the authors: thromboembolic disease, joint-specific reasons, surgical site infection, and surgical sequelae. The diagnoses in these categories are listed in Table 1. Other extracted reasons were cardiac dysrhythmia and pneumonia.

In cases in which there were at least 2 comparable studies, a meta-analysis was performed to obtain pooled estimates of the proportion of patients readmitted at 30 or 90 days. We calculated a Higgins I² measure for between-study heterogeneity and random-effects analysis, using the method of DerSimonian and Laird²³ if I² was greater than 0.5. Pooled estimates were obtained for both overall and cause-specific reasons for readmission for all reasons reported in at least 3 studies. Small-study or publication bias was assessed using funnel plot asymmetry when at least 5 studies were analyzed as recommended.²⁴ The meta-analytic findings for both overall and cause-specific readmission are presented as pooled proportions with 95% confidence intervals (CIs). All meta-analyses were performed using Stata 10.0.

Results

Fifteen unique TJA studies (12 THA, 10 TKA) met the criteria for the meta-analysis.^20,25-38Figure 1 depicts the PRISMA flowchart for study identification.²²

Of the 12 studies eligible for the THA analysis (Table 2), 6 were conducted in the United States,^{20,26,27,30,33,34} 5 in Europe,^{25,28,29,32,35} and 1 in Canada.³¹ Seven of the 12 studies reported readmission rates at 30 days, and 7 reported rates at 90 days (2 reported rates at both follow-ups). We analyzed a total of 113,396 patients at the 30-day window and 192,380 patients at the 90-day window. Mean age was 74.2 years. The included studies were variable and sparse in their reporting of specific characteristics (Table 3).

Of the 10 studies (2 prospective, 8 retrospective) eligible for the TKA analysis (Table 4), 6 were conducted in the United States,^{20,26,27,34,36,37} 3 in Europe,^25,29,35 and 1 in Asia.³⁸ Four of the 10 studies reported readmission rates at 30 days, and 7 reported rates at 90 days (1 reported rates at both follow-ups).²⁷ We analyzed a total of 3,278,635 patients at the 30-day window and 272,419 patients at the 90-day window. Mean age was 74.3 years. The included studies were quite variable and sparse in their reporting of specific characteristics (Table 5).

We performed random-effects meta-analyses of all unplanned readmissions at both 30 and 90 days (all I²s > 0.5). Among 5 THA studies that reported overall rates at 30 days,^{20,27,28,32,33} the estimated overall unplanned rate among the 120,272 index surgeries was 5.6% (95% CI, 3.2%-8.0%). Among 5 THA studies that reported overall rates at 90 days,^20,25-27,31 the estimated overall unplanned rate among the 192,380 index surgeries was 7.7% (95% CI, 3.2%-12.2%) (I² = 1.00). Among 3 TKA studies that reported overall rates at 30 days,^27,37,38 the estimated overall unplanned rate among the 3,278,635 index surgeries was 3.3% (95% CI, 0.7%-5.9%). Among 5 TKA studies that reported overall rates at 90 days,^20,25-27,36 the estimated overall unplanned rate among the 272,419 index surgeries was 9.7% (95% CI, 7.1%-12.4%) (I² = 0.97).

30-Day Readmission Rates

The most common reason for readmission 30 days after THA discharge was joint-specific. This reason accounted for 39.3% of all unplanned readmissions among studies that reported joint-specific causes, with an estimated pooled rate of 2.2% (95% CI, 0.0%-4.6%; P < .001; I² = 1.00) among 4 studies. The second and third most common reasons were surgical sequelae (1.6%; 95% CI, 0.8%-2.5%; P < .001; I² = 0.95) and thromboembolic disease (1.5%; 95% CI, 1.0%-1.9%; P < .001; I² = 0.95). See Figure 2 for 30-day THA readmission rates. The fourth most common readmission reason was surgical site infection (0.6%; 95% CI, 0.2%-1.1%; P < .001; I² = 0.94). Only these 4 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and bleeding were reported in only 1 study each.

The most common reason for readmission 30 days after TKA discharge was surgical site infection. This reason accounted for 12.1% of all unplanned readmissions among studies that reported surgical site infections, with an estimated pooled rate of 0.4% (95% CI, 0.3%-0.6%; P < .001; I² = 0.61) among 3 studies. The second and third most common reasons were joint-specific and thromboembolic disease, both occurring 0.3% of the time. Joint-specific reasons were reported in 2 studies (95% CI, 0.0%-0.8%; P = .259; I² = 0.94). Thromboembolic disease was reported in 4 studies (95% CI, 0.0%-0.7%; P = .067; I² = 0.98) (Figure 3). Only these 3 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and “sequelae” were reported in only 1 study each.

90-Day Readmission Rates

Consistent with the 30-day THA results, the most common reason for readmission 90 days after THA discharge was joint-specific. This reason accounted for 31.2% of all unplanned readmissions among studies that reported joint-specific causes, with an estimated pooled rate of 2.4% (95% CI, 0.0%-4.9%; P < .001; I² = 1.00) among 5 studies. The second and third most common reasons were surgical sequelae (1.6%; 95% CI, 1.0%-2.2%; P < .003; I² = 0.83) and thromboembolic disease (1.0%; 95% CI, 0.7%-1.4%; P < .001; I² = 0.97). See Figure 4 for 90-day THA readmission rates. The fourth most common readmission reason was surgical site infection (0.6%; 95% CI, 0.2%-1.0%; P < .001; I² = 0.99). Only these 4 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and bleeding were reported by only 1 study each.

Consistent with the 30-day TKA results, the most common reason for readmission 90 days after TKA discharge was surgical site infection. This reason accounted for 9.3% of all unplanned readmissions among studies that reported surgical site infections, with an estimated pooled rate of 0.9% (95% CI, 0.4%-1.4%; P < .001; I² = 0.93) among 5 studies. The second and third most common reasons were joint-specific and thromboembolic disease, both occurring 0.7% of the time. Joint-specific reasons were reported in 5 studies (95% CI, 0.2%-1.1%; P =.003; I² = 0.94). Thromboembolic disease was reported in 7 studies (95% CI, 0.3%-1.1%; P < .001; I² = 0.97) (Figure 5). Bleeding was reported in 3 studies, with a pooled rate of 0.4% (95% CI, 0.0%-0.9%; P = .128; I² = 0.83). Cardiac dysrhythmia was reported in 2 studies, with an estimated pooled rate of 0.3% (95% CI, 0.2%-0.5%; P < .001). Only these 5 reasons could be pooled, as pneumonia and “sequelae” were reported in only 1 study each.

Discussion

This study is the first systematic review and meta-analysis of the literature to identify overall and cause-specific readmission rates after TJA.

For THA, 30- and 90-day readmission rates were 5.6% and 7.7%, respectively. Joint-specific causes were the most common reason for readmission at both 30 and 90 days after THA. For TKA, 30- and 90-day rates were 3.3% and 9.7%, respectively. Surgical site infection was the most common reason for readmission at both 30 and 90 days after TKA.

Hospital readmissions are an important area of scrutiny for Medicare and the health care systems broadly. Readmissions after surgery are deemed quality indicators potentially suggesting incomplete management of active issues and inadequate preparation for discharge.³⁹ Unplanned readmissions also place a significant economic burden on Medicare: $17.5 billion in 2010.⁴⁰ Given their association with quality of overall surgical care, improved readmission rates have the potential to improve the standard of care and reduce costs.

Higher readmission rates will significantly affect hospitals as CMS shifts to bundling payments for acute-care episodes, such as TJA.^41-43 Further, private and public health care payers are increasingly using unplanned 30- and 90-day readmission rates as a marker of quality of care. However, there is little agreement about readmission rates and reasons, let alone what follow-up window should be used to define orthopedic readmissions. One study involving the MEDPAR (Medicare Provider Analysis and Review) database found that a common reason for readmission after major hip or knee surgery was “aftercare” for surgical sequelae (10.3%)¹⁵; another study found a 15% increase in post-THA hospitalizations, most commonly for a mechanical complication (joint-related).⁴⁴ There are no prior complete systematic reviews or meta-analyses of overall rates of readmissions after primary unilateral TJAs, or of the reasons for these readmissions. The closest such report, the Yale report to CMS, was skewed to a proportion of US hospitals treating a population prone to significant comorbidities.²⁰

Although the strength of this study lies in its rigorous identification and extraction of data, notable clarifications must be made when synthesizing the information. First, the definitions of various thromboembolic events varied greatly. Some studies reported deep vein thrombosis (DVT) and pulmonary embolism (PE) separately, whereas others reported only DVT or only PE. Some studies reported rates of readmission for “thromboembolic disorder,” and one²⁵ reported rates for DVT, PE, and thromboembolic disorder. To pool these related events, we created a composite definition that included DVT, PE, and thromboembolic disorders, which we termed thromboembolic disease. We also created a composite measure for joint-specific reasons for readmission. This category included joint infection that definitely required reentry into the joint, but using this category may have led to underestimation of surgical site infection rates, which were defined separately. Third, there was significant variation in documentation of surgical site infection among the studies included in this review. Some studies specified superficial wounds, whereas others did not categorize complications as superficial, deep, or intracapsular, which would qualify as a “joint-specific” cause. Despite this variation, surgical site infection after TJA was found to be the most common reason for readmission.

Our systematic review and meta-analysis were limited, as any others are, by the quality of studies investigated. Few studies reported cause-specific rates and reasons for readmission. Given the small sample, formal tests for small-study or publication bias could not be performed. Some studies included tremendous amounts of data, and International Classification of Diseases, Ninth Revision (ICD-9) codes were used without physician review of readmission diagnoses. In the absence of oversight, many readmissions could have been misinterpreted and incorrectly logged, or simply miscoded. Saucedo and colleagues^27,45 found that readmission diagnostic codes were often unverified. Numerous other studies corroborated this lack of correlation with physician-derived readmission diagnoses in just 25% of cases.^46-54 Another study limitation is the unknown number of patients who had TJA but presented and were subsequently readmitted to a different hospital. Last, as this review included patients who had surgery performed within a 30-year period, it could not address the shifts in postoperative management that occurred in that time, particularly with respect to anticoagulation. This limitation was partially addressed in THA by dividing final studies into 3 decades. Of these studies, only 1 was from the first decade, 3 were from the second, and the rest were from the third. Of the 3 from the second decade, only the study by Warwick and colleagues²⁹ (1995) explicitly did not use anticoagulation, but compression stockings were used, and consequently there was a 4.0% rate of readmission for thromboembolic disease alone, compared with the study by White and colleagues³⁴ (1998), which explicitly used anticoagulation and boasted a 1.7% rate of readmission for thromboembolic disease. This isolated comparison illustrates the effect of routine anticoagulation and the changes in surgical standards over the 3 decades.

The numbers from this systematic review and meta-analysis represent an international benchmark for TJA as a procedure. Knowing the top reasons for readmission will lead to more focus on joint-related and medical issues (surgical site infection, thromboembolic disease) before discharge to avoid readmission after elective unilateral primary TJA. Although readmission rates have received attention in the United States as a primary means of combating soaring health care costs, knowing the rates for a common procedure applies broadly as an indicator for standard of care worldwide, according to the World Health Organization.⁵⁵ This study is the first systematic review and meta-analysis of documented readmission rates and reasons for readmission to identify overall and cause-specific rates after TJA. The hope is that our findings will add clarity to the literature and help guide the decisions of physicians and policymakers.

Conclusion

Readmission rates are an increasingly important metric in the United States and around the world, yet there is no consensus regarding overall readmission rates and reasons for readmission after primary unilateral TJAs. Our systematic review and meta-analysis of the literature found overall unplanned readmission rates of 5.6% (30 days) and 7.7% (90 days) for THA and 3.3% (30 days) and 9.7% (90 days) for TKA. At both 30 and 90 days, the most common readmission reasons were joint-specific (THA) and surgical site infection (TKA). New investigations should be directed toward developing countermeasures to lower the rates of readmission.

Total joint arthroplasty (TJA) is a clinically effective, cost-effective treatment for symptomatic arthritis.^1,2 After TJA, patients report reduced pain, restored range of motion, high satisfaction, and ability to return to a more active lifestyle.^3-7 The number of total hip arthroplasties (THAs) performed in the United States is expected to reach 572,000 by 2030, a 174% increase, and the number of total knee arthroplasties (TKAs) 3.5 million, nearly a 7-fold increase.^8,9 Since 2005, the cost of THA has risen more than 4 times, to $13.43 billion, and the cost of TKA has risen more than 5 times, to $40.8 billion.^8,9 Given the demand and price tag, TJA is the single largest cost in the Medicare budget.¹⁰

Given its potential to improve care and reduce costs, reducing readmission rates in the surgical setting is a priority for physicians and policymakers.¹¹ Readmissions for TJA are highly scrutinized as a performance indicator—the Centers for Medicare & Medicaid Services (CMS) started including them in its readmissions penalty program in 2013—and were recently validated as a measure of surgical quality.^12-14 Accurate assessments of readmissions after TJA are unclear, with rates ranging from 1% to 8.5% between 7 and 90 days after surgery.^2,15-17 The early success of TJA as an elective (and more frequently outpatient) procedure has paradoxically translated to less tolerance for readmissions. Post-TJA complications resulting in readmission are subject to financial penalties, and there is an implicit judgment of inadequate surgical management.¹²

Not only is the readmission rate poorly characterized, but there is no consensus on the leading reasons for readmissions after primary elective unilateral TJAs. The range of rates, reasons, and follow-up periods reported in the literature is wide.^18,19 CMS plans to monitor readmissions over 7 to 90 days after surgery (the period depends on the complication), whereas a significant portion of the orthopedic literature documents 90-day rates.¹⁹ In 2012, the Yale New Haven Health Services Corporation/Center for Outcomes Research and Evaluation prepared for CMS a comprehensive report identifying rates of post-TJA complications and readmissions.²⁰ The report, however, is limited to US hospitals and Medicare patients and therefore may overstate the rates, given this population’s documented comorbidities and the reimbursement variations between Medicare and commercial insurance.²¹ Lack of consensus on readmissions after primary elective unilateral TJAs requires that we synthesize available data to answer several questions: What is the overall readmission rate 30 and 90 days after TJA? What are the primary reasons for readmission 30 and 90 days after TJA? What are the cause-specific readmission rates? We performed a systematic review and a meta-analysis to answer these questions and to add clarity to the literature in order to help guide policy.

Materials and Methods

We performed a systematic review in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.²² Two reviewers independently completed structured searches of the Medline and Cochrane Central Register of Controlled Trials databases. Search terms were: (total hip replacement OR hip arthroplasty OR total hip arthroplasty OR total knee replacement OR knee arthroplasty OR total knee arthroplasty) AND (readmission OR complication OR discharge). They updated the search June 1, 2013. Four limits were applied: publication between January 1, 1982 and December 12, 2012; human subjects only; age 19+ years; and English-language articles. Study eligibility was determined by using standardized criteria as defined by the inclusion and exclusion criteria described in 3 stages: title review, abstract review, and full-article review. The reviewers also performed ancestry searches, including searches for major review articles and bibliographies of all retrieved studies, to identify additional studies not identified in the keyword searches. Discrepancies were resolved by author consensus.

Inclusion criteria were original studies that presented level I to III evidence and that were identified in structured online searches; published in English between January 1, 1982 and December 31, 2012; involved patients older than 19 years; and reported both readmission rates and reasons at follow-up 30 or 90 days after elective primary unilateral TJA, regardless of indication. Exclusion criteria were studies that reported data from hip fracture, knee fracture, and pelvis fracture cases; those that reported data from hemiarthroplasty, Birmingham hip resurfacing procedures, other resurfacing procedures, simultaneous bilateral hip or knee arthroplasties, unicompartmental knee arthroplasty, patellofemoral arthroplasty, metastatic or bone cancer, or revision hip or knee arthroplasty; those that did not report extractable reasons for readmission; those that reported complications but did not specify readmission rates; and those that reported readmission data only from after the 90-day follow-up window. In cases in which multiple studies reported data from the same patient population, only the largest or most recent report was used.

Two reviewers extracted the quantitative data from eligible studies. The 2 primary outcomes of interests were all-cause readmission rates, and reasons for readmission 30 and 90 days after TJA. Other extracted data were evidence level; publication journal, year, and country; data source (academic institution, Medicare); study design; number of patients; patient characteristics; surgical approach; follow-up period; overall readmission rate; anticoagulant use; tourniquet use; and compression stocking use. In addition, all post-TJA readmissions were assumed to be unplanned, except for staged sequential bilateral arthroplasty for osteoarthritis (excluded from analysis).

Readmission reasons were divided into 4 major categories as defined by the literature and the authors: thromboembolic disease, joint-specific reasons, surgical site infection, and surgical sequelae. The diagnoses in these categories are listed in Table 1. Other extracted reasons were cardiac dysrhythmia and pneumonia.

In cases in which there were at least 2 comparable studies, a meta-analysis was performed to obtain pooled estimates of the proportion of patients readmitted at 30 or 90 days. We calculated a Higgins I² measure for between-study heterogeneity and random-effects analysis, using the method of DerSimonian and Laird²³ if I² was greater than 0.5. Pooled estimates were obtained for both overall and cause-specific reasons for readmission for all reasons reported in at least 3 studies. Small-study or publication bias was assessed using funnel plot asymmetry when at least 5 studies were analyzed as recommended.²⁴ The meta-analytic findings for both overall and cause-specific readmission are presented as pooled proportions with 95% confidence intervals (CIs). All meta-analyses were performed using Stata 10.0.

Results

Fifteen unique TJA studies (12 THA, 10 TKA) met the criteria for the meta-analysis.^20,25-38Figure 1 depicts the PRISMA flowchart for study identification.²²

Of the 12 studies eligible for the THA analysis (Table 2), 6 were conducted in the United States,^{20,26,27,30,33,34} 5 in Europe,^{25,28,29,32,35} and 1 in Canada.³¹ Seven of the 12 studies reported readmission rates at 30 days, and 7 reported rates at 90 days (2 reported rates at both follow-ups). We analyzed a total of 113,396 patients at the 30-day window and 192,380 patients at the 90-day window. Mean age was 74.2 years. The included studies were variable and sparse in their reporting of specific characteristics (Table 3).

Of the 10 studies (2 prospective, 8 retrospective) eligible for the TKA analysis (Table 4), 6 were conducted in the United States,^{20,26,27,34,36,37} 3 in Europe,^25,29,35 and 1 in Asia.³⁸ Four of the 10 studies reported readmission rates at 30 days, and 7 reported rates at 90 days (1 reported rates at both follow-ups).²⁷ We analyzed a total of 3,278,635 patients at the 30-day window and 272,419 patients at the 90-day window. Mean age was 74.3 years. The included studies were quite variable and sparse in their reporting of specific characteristics (Table 5).

We performed random-effects meta-analyses of all unplanned readmissions at both 30 and 90 days (all I²s > 0.5). Among 5 THA studies that reported overall rates at 30 days,^{20,27,28,32,33} the estimated overall unplanned rate among the 120,272 index surgeries was 5.6% (95% CI, 3.2%-8.0%). Among 5 THA studies that reported overall rates at 90 days,^20,25-27,31 the estimated overall unplanned rate among the 192,380 index surgeries was 7.7% (95% CI, 3.2%-12.2%) (I² = 1.00). Among 3 TKA studies that reported overall rates at 30 days,^27,37,38 the estimated overall unplanned rate among the 3,278,635 index surgeries was 3.3% (95% CI, 0.7%-5.9%). Among 5 TKA studies that reported overall rates at 90 days,^20,25-27,36 the estimated overall unplanned rate among the 272,419 index surgeries was 9.7% (95% CI, 7.1%-12.4%) (I² = 0.97).

30-Day Readmission Rates

The most common reason for readmission 30 days after THA discharge was joint-specific. This reason accounted for 39.3% of all unplanned readmissions among studies that reported joint-specific causes, with an estimated pooled rate of 2.2% (95% CI, 0.0%-4.6%; P < .001; I² = 1.00) among 4 studies. The second and third most common reasons were surgical sequelae (1.6%; 95% CI, 0.8%-2.5%; P < .001; I² = 0.95) and thromboembolic disease (1.5%; 95% CI, 1.0%-1.9%; P < .001; I² = 0.95). See Figure 2 for 30-day THA readmission rates. The fourth most common readmission reason was surgical site infection (0.6%; 95% CI, 0.2%-1.1%; P < .001; I² = 0.94). Only these 4 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and bleeding were reported in only 1 study each.

The most common reason for readmission 30 days after TKA discharge was surgical site infection. This reason accounted for 12.1% of all unplanned readmissions among studies that reported surgical site infections, with an estimated pooled rate of 0.4% (95% CI, 0.3%-0.6%; P < .001; I² = 0.61) among 3 studies. The second and third most common reasons were joint-specific and thromboembolic disease, both occurring 0.3% of the time. Joint-specific reasons were reported in 2 studies (95% CI, 0.0%-0.8%; P = .259; I² = 0.94). Thromboembolic disease was reported in 4 studies (95% CI, 0.0%-0.7%; P = .067; I² = 0.98) (Figure 3). Only these 3 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and “sequelae” were reported in only 1 study each.

90-Day Readmission Rates

Consistent with the 30-day THA results, the most common reason for readmission 90 days after THA discharge was joint-specific. This reason accounted for 31.2% of all unplanned readmissions among studies that reported joint-specific causes, with an estimated pooled rate of 2.4% (95% CI, 0.0%-4.9%; P < .001; I² = 1.00) among 5 studies. The second and third most common reasons were surgical sequelae (1.6%; 95% CI, 1.0%-2.2%; P < .003; I² = 0.83) and thromboembolic disease (1.0%; 95% CI, 0.7%-1.4%; P < .001; I² = 0.97). See Figure 4 for 90-day THA readmission rates. The fourth most common readmission reason was surgical site infection (0.6%; 95% CI, 0.2%-1.0%; P < .001; I² = 0.99). Only these 4 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and bleeding were reported by only 1 study each.

Consistent with the 30-day TKA results, the most common reason for readmission 90 days after TKA discharge was surgical site infection. This reason accounted for 9.3% of all unplanned readmissions among studies that reported surgical site infections, with an estimated pooled rate of 0.9% (95% CI, 0.4%-1.4%; P < .001; I² = 0.93) among 5 studies. The second and third most common reasons were joint-specific and thromboembolic disease, both occurring 0.7% of the time. Joint-specific reasons were reported in 5 studies (95% CI, 0.2%-1.1%; P =.003; I² = 0.94). Thromboembolic disease was reported in 7 studies (95% CI, 0.3%-1.1%; P < .001; I² = 0.97) (Figure 5). Bleeding was reported in 3 studies, with a pooled rate of 0.4% (95% CI, 0.0%-0.9%; P = .128; I² = 0.83). Cardiac dysrhythmia was reported in 2 studies, with an estimated pooled rate of 0.3% (95% CI, 0.2%-0.5%; P < .001). Only these 5 reasons could be pooled, as pneumonia and “sequelae” were reported in only 1 study each.

Discussion

This study is the first systematic review and meta-analysis of the literature to identify overall and cause-specific readmission rates after TJA.

For THA, 30- and 90-day readmission rates were 5.6% and 7.7%, respectively. Joint-specific causes were the most common reason for readmission at both 30 and 90 days after THA. For TKA, 30- and 90-day rates were 3.3% and 9.7%, respectively. Surgical site infection was the most common reason for readmission at both 30 and 90 days after TKA.

Hospital readmissions are an important area of scrutiny for Medicare and the health care systems broadly. Readmissions after surgery are deemed quality indicators potentially suggesting incomplete management of active issues and inadequate preparation for discharge.³⁹ Unplanned readmissions also place a significant economic burden on Medicare: $17.5 billion in 2010.⁴⁰ Given their association with quality of overall surgical care, improved readmission rates have the potential to improve the standard of care and reduce costs.

Higher readmission rates will significantly affect hospitals as CMS shifts to bundling payments for acute-care episodes, such as TJA.^41-43 Further, private and public health care payers are increasingly using unplanned 30- and 90-day readmission rates as a marker of quality of care. However, there is little agreement about readmission rates and reasons, let alone what follow-up window should be used to define orthopedic readmissions. One study involving the MEDPAR (Medicare Provider Analysis and Review) database found that a common reason for readmission after major hip or knee surgery was “aftercare” for surgical sequelae (10.3%)¹⁵; another study found a 15% increase in post-THA hospitalizations, most commonly for a mechanical complication (joint-related).⁴⁴ There are no prior complete systematic reviews or meta-analyses of overall rates of readmissions after primary unilateral TJAs, or of the reasons for these readmissions. The closest such report, the Yale report to CMS, was skewed to a proportion of US hospitals treating a population prone to significant comorbidities.²⁰

Although the strength of this study lies in its rigorous identification and extraction of data, notable clarifications must be made when synthesizing the information. First, the definitions of various thromboembolic events varied greatly. Some studies reported deep vein thrombosis (DVT) and pulmonary embolism (PE) separately, whereas others reported only DVT or only PE. Some studies reported rates of readmission for “thromboembolic disorder,” and one²⁵ reported rates for DVT, PE, and thromboembolic disorder. To pool these related events, we created a composite definition that included DVT, PE, and thromboembolic disorders, which we termed thromboembolic disease. We also created a composite measure for joint-specific reasons for readmission. This category included joint infection that definitely required reentry into the joint, but using this category may have led to underestimation of surgical site infection rates, which were defined separately. Third, there was significant variation in documentation of surgical site infection among the studies included in this review. Some studies specified superficial wounds, whereas others did not categorize complications as superficial, deep, or intracapsular, which would qualify as a “joint-specific” cause. Despite this variation, surgical site infection after TJA was found to be the most common reason for readmission.

Our systematic review and meta-analysis were limited, as any others are, by the quality of studies investigated. Few studies reported cause-specific rates and reasons for readmission. Given the small sample, formal tests for small-study or publication bias could not be performed. Some studies included tremendous amounts of data, and International Classification of Diseases, Ninth Revision (ICD-9) codes were used without physician review of readmission diagnoses. In the absence of oversight, many readmissions could have been misinterpreted and incorrectly logged, or simply miscoded. Saucedo and colleagues^27,45 found that readmission diagnostic codes were often unverified. Numerous other studies corroborated this lack of correlation with physician-derived readmission diagnoses in just 25% of cases.^46-54 Another study limitation is the unknown number of patients who had TJA but presented and were subsequently readmitted to a different hospital. Last, as this review included patients who had surgery performed within a 30-year period, it could not address the shifts in postoperative management that occurred in that time, particularly with respect to anticoagulation. This limitation was partially addressed in THA by dividing final studies into 3 decades. Of these studies, only 1 was from the first decade, 3 were from the second, and the rest were from the third. Of the 3 from the second decade, only the study by Warwick and colleagues²⁹ (1995) explicitly did not use anticoagulation, but compression stockings were used, and consequently there was a 4.0% rate of readmission for thromboembolic disease alone, compared with the study by White and colleagues³⁴ (1998), which explicitly used anticoagulation and boasted a 1.7% rate of readmission for thromboembolic disease. This isolated comparison illustrates the effect of routine anticoagulation and the changes in surgical standards over the 3 decades.

The numbers from this systematic review and meta-analysis represent an international benchmark for TJA as a procedure. Knowing the top reasons for readmission will lead to more focus on joint-related and medical issues (surgical site infection, thromboembolic disease) before discharge to avoid readmission after elective unilateral primary TJA. Although readmission rates have received attention in the United States as a primary means of combating soaring health care costs, knowing the rates for a common procedure applies broadly as an indicator for standard of care worldwide, according to the World Health Organization.⁵⁵ This study is the first systematic review and meta-analysis of documented readmission rates and reasons for readmission to identify overall and cause-specific rates after TJA. The hope is that our findings will add clarity to the literature and help guide the decisions of physicians and policymakers.

Conclusion

Readmission rates are an increasingly important metric in the United States and around the world, yet there is no consensus regarding overall readmission rates and reasons for readmission after primary unilateral TJAs. Our systematic review and meta-analysis of the literature found overall unplanned readmission rates of 5.6% (30 days) and 7.7% (90 days) for THA and 3.3% (30 days) and 9.7% (90 days) for TKA. At both 30 and 90 days, the most common readmission reasons were joint-specific (THA) and surgical site infection (TKA). New investigations should be directed toward developing countermeasures to lower the rates of readmission.

Total joint arthroplasty (TJA) is a clinically effective, cost-effective treatment for symptomatic arthritis.^1,2 After TJA, patients report reduced pain, restored range of motion, high satisfaction, and ability to return to a more active lifestyle.^3-7 The number of total hip arthroplasties (THAs) performed in the United States is expected to reach 572,000 by 2030, a 174% increase, and the number of total knee arthroplasties (TKAs) 3.5 million, nearly a 7-fold increase.^8,9 Since 2005, the cost of THA has risen more than 4 times, to $13.43 billion, and the cost of TKA has risen more than 5 times, to $40.8 billion.^8,9 Given the demand and price tag, TJA is the single largest cost in the Medicare budget.¹⁰

Given its potential to improve care and reduce costs, reducing readmission rates in the surgical setting is a priority for physicians and policymakers.¹¹ Readmissions for TJA are highly scrutinized as a performance indicator—the Centers for Medicare & Medicaid Services (CMS) started including them in its readmissions penalty program in 2013—and were recently validated as a measure of surgical quality.^12-14 Accurate assessments of readmissions after TJA are unclear, with rates ranging from 1% to 8.5% between 7 and 90 days after surgery.^2,15-17 The early success of TJA as an elective (and more frequently outpatient) procedure has paradoxically translated to less tolerance for readmissions. Post-TJA complications resulting in readmission are subject to financial penalties, and there is an implicit judgment of inadequate surgical management.¹²

Not only is the readmission rate poorly characterized, but there is no consensus on the leading reasons for readmissions after primary elective unilateral TJAs. The range of rates, reasons, and follow-up periods reported in the literature is wide.^18,19 CMS plans to monitor readmissions over 7 to 90 days after surgery (the period depends on the complication), whereas a significant portion of the orthopedic literature documents 90-day rates.¹⁹ In 2012, the Yale New Haven Health Services Corporation/Center for Outcomes Research and Evaluation prepared for CMS a comprehensive report identifying rates of post-TJA complications and readmissions.²⁰ The report, however, is limited to US hospitals and Medicare patients and therefore may overstate the rates, given this population’s documented comorbidities and the reimbursement variations between Medicare and commercial insurance.²¹ Lack of consensus on readmissions after primary elective unilateral TJAs requires that we synthesize available data to answer several questions: What is the overall readmission rate 30 and 90 days after TJA? What are the primary reasons for readmission 30 and 90 days after TJA? What are the cause-specific readmission rates? We performed a systematic review and a meta-analysis to answer these questions and to add clarity to the literature in order to help guide policy.

Materials and Methods

We performed a systematic review in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.²² Two reviewers independently completed structured searches of the Medline and Cochrane Central Register of Controlled Trials databases. Search terms were: (total hip replacement OR hip arthroplasty OR total hip arthroplasty OR total knee replacement OR knee arthroplasty OR total knee arthroplasty) AND (readmission OR complication OR discharge). They updated the search June 1, 2013. Four limits were applied: publication between January 1, 1982 and December 12, 2012; human subjects only; age 19+ years; and English-language articles. Study eligibility was determined by using standardized criteria as defined by the inclusion and exclusion criteria described in 3 stages: title review, abstract review, and full-article review. The reviewers also performed ancestry searches, including searches for major review articles and bibliographies of all retrieved studies, to identify additional studies not identified in the keyword searches. Discrepancies were resolved by author consensus.

Inclusion criteria were original studies that presented level I to III evidence and that were identified in structured online searches; published in English between January 1, 1982 and December 31, 2012; involved patients older than 19 years; and reported both readmission rates and reasons at follow-up 30 or 90 days after elective primary unilateral TJA, regardless of indication. Exclusion criteria were studies that reported data from hip fracture, knee fracture, and pelvis fracture cases; those that reported data from hemiarthroplasty, Birmingham hip resurfacing procedures, other resurfacing procedures, simultaneous bilateral hip or knee arthroplasties, unicompartmental knee arthroplasty, patellofemoral arthroplasty, metastatic or bone cancer, or revision hip or knee arthroplasty; those that did not report extractable reasons for readmission; those that reported complications but did not specify readmission rates; and those that reported readmission data only from after the 90-day follow-up window. In cases in which multiple studies reported data from the same patient population, only the largest or most recent report was used.

Two reviewers extracted the quantitative data from eligible studies. The 2 primary outcomes of interests were all-cause readmission rates, and reasons for readmission 30 and 90 days after TJA. Other extracted data were evidence level; publication journal, year, and country; data source (academic institution, Medicare); study design; number of patients; patient characteristics; surgical approach; follow-up period; overall readmission rate; anticoagulant use; tourniquet use; and compression stocking use. In addition, all post-TJA readmissions were assumed to be unplanned, except for staged sequential bilateral arthroplasty for osteoarthritis (excluded from analysis).

Readmission reasons were divided into 4 major categories as defined by the literature and the authors: thromboembolic disease, joint-specific reasons, surgical site infection, and surgical sequelae. The diagnoses in these categories are listed in Table 1. Other extracted reasons were cardiac dysrhythmia and pneumonia.

In cases in which there were at least 2 comparable studies, a meta-analysis was performed to obtain pooled estimates of the proportion of patients readmitted at 30 or 90 days. We calculated a Higgins I² measure for between-study heterogeneity and random-effects analysis, using the method of DerSimonian and Laird²³ if I² was greater than 0.5. Pooled estimates were obtained for both overall and cause-specific reasons for readmission for all reasons reported in at least 3 studies. Small-study or publication bias was assessed using funnel plot asymmetry when at least 5 studies were analyzed as recommended.²⁴ The meta-analytic findings for both overall and cause-specific readmission are presented as pooled proportions with 95% confidence intervals (CIs). All meta-analyses were performed using Stata 10.0.

Results

Fifteen unique TJA studies (12 THA, 10 TKA) met the criteria for the meta-analysis.^20,25-38Figure 1 depicts the PRISMA flowchart for study identification.²²

Of the 12 studies eligible for the THA analysis (Table 2), 6 were conducted in the United States,^{20,26,27,30,33,34} 5 in Europe,^{25,28,29,32,35} and 1 in Canada.³¹ Seven of the 12 studies reported readmission rates at 30 days, and 7 reported rates at 90 days (2 reported rates at both follow-ups). We analyzed a total of 113,396 patients at the 30-day window and 192,380 patients at the 90-day window. Mean age was 74.2 years. The included studies were variable and sparse in their reporting of specific characteristics (Table 3).

Of the 10 studies (2 prospective, 8 retrospective) eligible for the TKA analysis (Table 4), 6 were conducted in the United States,^{20,26,27,34,36,37} 3 in Europe,^25,29,35 and 1 in Asia.³⁸ Four of the 10 studies reported readmission rates at 30 days, and 7 reported rates at 90 days (1 reported rates at both follow-ups).²⁷ We analyzed a total of 3,278,635 patients at the 30-day window and 272,419 patients at the 90-day window. Mean age was 74.3 years. The included studies were quite variable and sparse in their reporting of specific characteristics (Table 5).

We performed random-effects meta-analyses of all unplanned readmissions at both 30 and 90 days (all I²s > 0.5). Among 5 THA studies that reported overall rates at 30 days,^{20,27,28,32,33} the estimated overall unplanned rate among the 120,272 index surgeries was 5.6% (95% CI, 3.2%-8.0%). Among 5 THA studies that reported overall rates at 90 days,^20,25-27,31 the estimated overall unplanned rate among the 192,380 index surgeries was 7.7% (95% CI, 3.2%-12.2%) (I² = 1.00). Among 3 TKA studies that reported overall rates at 30 days,^27,37,38 the estimated overall unplanned rate among the 3,278,635 index surgeries was 3.3% (95% CI, 0.7%-5.9%). Among 5 TKA studies that reported overall rates at 90 days,^20,25-27,36 the estimated overall unplanned rate among the 272,419 index surgeries was 9.7% (95% CI, 7.1%-12.4%) (I² = 0.97).

30-Day Readmission Rates

The most common reason for readmission 30 days after THA discharge was joint-specific. This reason accounted for 39.3% of all unplanned readmissions among studies that reported joint-specific causes, with an estimated pooled rate of 2.2% (95% CI, 0.0%-4.6%; P < .001; I² = 1.00) among 4 studies. The second and third most common reasons were surgical sequelae (1.6%; 95% CI, 0.8%-2.5%; P < .001; I² = 0.95) and thromboembolic disease (1.5%; 95% CI, 1.0%-1.9%; P < .001; I² = 0.95). See Figure 2 for 30-day THA readmission rates. The fourth most common readmission reason was surgical site infection (0.6%; 95% CI, 0.2%-1.1%; P < .001; I² = 0.94). Only these 4 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and bleeding were reported in only 1 study each.

The most common reason for readmission 30 days after TKA discharge was surgical site infection. This reason accounted for 12.1% of all unplanned readmissions among studies that reported surgical site infections, with an estimated pooled rate of 0.4% (95% CI, 0.3%-0.6%; P < .001; I² = 0.61) among 3 studies. The second and third most common reasons were joint-specific and thromboembolic disease, both occurring 0.3% of the time. Joint-specific reasons were reported in 2 studies (95% CI, 0.0%-0.8%; P = .259; I² = 0.94). Thromboembolic disease was reported in 4 studies (95% CI, 0.0%-0.7%; P = .067; I² = 0.98) (Figure 3). Only these 3 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and “sequelae” were reported in only 1 study each.

90-Day Readmission Rates

Consistent with the 30-day THA results, the most common reason for readmission 90 days after THA discharge was joint-specific. This reason accounted for 31.2% of all unplanned readmissions among studies that reported joint-specific causes, with an estimated pooled rate of 2.4% (95% CI, 0.0%-4.9%; P < .001; I² = 1.00) among 5 studies. The second and third most common reasons were surgical sequelae (1.6%; 95% CI, 1.0%-2.2%; P < .003; I² = 0.83) and thromboembolic disease (1.0%; 95% CI, 0.7%-1.4%; P < .001; I² = 0.97). See Figure 4 for 90-day THA readmission rates. The fourth most common readmission reason was surgical site infection (0.6%; 95% CI, 0.2%-1.0%; P < .001; I² = 0.99). Only these 4 reasons could be pooled, as cardiac dysrhythmia, pneumonia, and bleeding were reported by only 1 study each.

Consistent with the 30-day TKA results, the most common reason for readmission 90 days after TKA discharge was surgical site infection. This reason accounted for 9.3% of all unplanned readmissions among studies that reported surgical site infections, with an estimated pooled rate of 0.9% (95% CI, 0.4%-1.4%; P < .001; I² = 0.93) among 5 studies. The second and third most common reasons were joint-specific and thromboembolic disease, both occurring 0.7% of the time. Joint-specific reasons were reported in 5 studies (95% CI, 0.2%-1.1%; P =.003; I² = 0.94). Thromboembolic disease was reported in 7 studies (95% CI, 0.3%-1.1%; P < .001; I² = 0.97) (Figure 5). Bleeding was reported in 3 studies, with a pooled rate of 0.4% (95% CI, 0.0%-0.9%; P = .128; I² = 0.83). Cardiac dysrhythmia was reported in 2 studies, with an estimated pooled rate of 0.3% (95% CI, 0.2%-0.5%; P < .001). Only these 5 reasons could be pooled, as pneumonia and “sequelae” were reported in only 1 study each.

Discussion

This study is the first systematic review and meta-analysis of the literature to identify overall and cause-specific readmission rates after TJA.

For THA, 30- and 90-day readmission rates were 5.6% and 7.7%, respectively. Joint-specific causes were the most common reason for readmission at both 30 and 90 days after THA. For TKA, 30- and 90-day rates were 3.3% and 9.7%, respectively. Surgical site infection was the most common reason for readmission at both 30 and 90 days after TKA.

Hospital readmissions are an important area of scrutiny for Medicare and the health care systems broadly. Readmissions after surgery are deemed quality indicators potentially suggesting incomplete management of active issues and inadequate preparation for discharge.³⁹ Unplanned readmissions also place a significant economic burden on Medicare: $17.5 billion in 2010.⁴⁰ Given their association with quality of overall surgical care, improved readmission rates have the potential to improve the standard of care and reduce costs.

Higher readmission rates will significantly affect hospitals as CMS shifts to bundling payments for acute-care episodes, such as TJA.^41-43 Further, private and public health care payers are increasingly using unplanned 30- and 90-day readmission rates as a marker of quality of care. However, there is little agreement about readmission rates and reasons, let alone what follow-up window should be used to define orthopedic readmissions. One study involving the MEDPAR (Medicare Provider Analysis and Review) database found that a common reason for readmission after major hip or knee surgery was “aftercare” for surgical sequelae (10.3%)¹⁵; another study found a 15% increase in post-THA hospitalizations, most commonly for a mechanical complication (joint-related).⁴⁴ There are no prior complete systematic reviews or meta-analyses of overall rates of readmissions after primary unilateral TJAs, or of the reasons for these readmissions. The closest such report, the Yale report to CMS, was skewed to a proportion of US hospitals treating a population prone to significant comorbidities.²⁰

Although the strength of this study lies in its rigorous identification and extraction of data, notable clarifications must be made when synthesizing the information. First, the definitions of various thromboembolic events varied greatly. Some studies reported deep vein thrombosis (DVT) and pulmonary embolism (PE) separately, whereas others reported only DVT or only PE. Some studies reported rates of readmission for “thromboembolic disorder,” and one²⁵ reported rates for DVT, PE, and thromboembolic disorder. To pool these related events, we created a composite definition that included DVT, PE, and thromboembolic disorders, which we termed thromboembolic disease. We also created a composite measure for joint-specific reasons for readmission. This category included joint infection that definitely required reentry into the joint, but using this category may have led to underestimation of surgical site infection rates, which were defined separately. Third, there was significant variation in documentation of surgical site infection among the studies included in this review. Some studies specified superficial wounds, whereas others did not categorize complications as superficial, deep, or intracapsular, which would qualify as a “joint-specific” cause. Despite this variation, surgical site infection after TJA was found to be the most common reason for readmission.

Our systematic review and meta-analysis were limited, as any others are, by the quality of studies investigated. Few studies reported cause-specific rates and reasons for readmission. Given the small sample, formal tests for small-study or publication bias could not be performed. Some studies included tremendous amounts of data, and International Classification of Diseases, Ninth Revision (ICD-9) codes were used without physician review of readmission diagnoses. In the absence of oversight, many readmissions could have been misinterpreted and incorrectly logged, or simply miscoded. Saucedo and colleagues^27,45 found that readmission diagnostic codes were often unverified. Numerous other studies corroborated this lack of correlation with physician-derived readmission diagnoses in just 25% of cases.^46-54 Another study limitation is the unknown number of patients who had TJA but presented and were subsequently readmitted to a different hospital. Last, as this review included patients who had surgery performed within a 30-year period, it could not address the shifts in postoperative management that occurred in that time, particularly with respect to anticoagulation. This limitation was partially addressed in THA by dividing final studies into 3 decades. Of these studies, only 1 was from the first decade, 3 were from the second, and the rest were from the third. Of the 3 from the second decade, only the study by Warwick and colleagues²⁹ (1995) explicitly did not use anticoagulation, but compression stockings were used, and consequently there was a 4.0% rate of readmission for thromboembolic disease alone, compared with the study by White and colleagues³⁴ (1998), which explicitly used anticoagulation and boasted a 1.7% rate of readmission for thromboembolic disease. This isolated comparison illustrates the effect of routine anticoagulation and the changes in surgical standards over the 3 decades.

The numbers from this systematic review and meta-analysis represent an international benchmark for TJA as a procedure. Knowing the top reasons for readmission will lead to more focus on joint-related and medical issues (surgical site infection, thromboembolic disease) before discharge to avoid readmission after elective unilateral primary TJA. Although readmission rates have received attention in the United States as a primary means of combating soaring health care costs, knowing the rates for a common procedure applies broadly as an indicator for standard of care worldwide, according to the World Health Organization.⁵⁵ This study is the first systematic review and meta-analysis of documented readmission rates and reasons for readmission to identify overall and cause-specific rates after TJA. The hope is that our findings will add clarity to the literature and help guide the decisions of physicians and policymakers.

Conclusion

Readmission rates are an increasingly important metric in the United States and around the world, yet there is no consensus regarding overall readmission rates and reasons for readmission after primary unilateral TJAs. Our systematic review and meta-analysis of the literature found overall unplanned readmission rates of 5.6% (30 days) and 7.7% (90 days) for THA and 3.3% (30 days) and 9.7% (90 days) for TKA. At both 30 and 90 days, the most common readmission reasons were joint-specific (THA) and surgical site infection (TKA). New investigations should be directed toward developing countermeasures to lower the rates of readmission.

The anterior cruciate ligament (ACL) restrains anterior translation of the tibia on the femur and controls rotation of the knee. The natural primary healing potential of the ACL has been extremely poor in clinical and experimental studies, and primary suture repair has not provided stability to the joint in most patients.^1-8 This has led surgeons to reconstruct the ACL, rather than to attempt nonoperative treatment. Anterior cruciate ligament reconstruction is recommended to help patients maintain activities that place shear and torque forces on the knee or to ameliorate persistent pain due to instability.⁹ Reconstruction of the ACL in adults is one of the most common procedures performed by orthopedic surgeons. However, reconstruction in the ACL-deficient adolescent remains a controversial subject, with debates surrounding operative timing and surgical technique.

This case report presents a skeletally immature patient who suffered a complete traumatic rupture of his ACL, which intrinsically healed. The patient had a protracted treatment course, complicated by an open tibial fracture with delayed union. He responded to a progressive rehabilitation program and has made a good functional recovery. Review of the literature has demonstrated limited evidence of intrinsic ACL healing, none of which has been shown to occur in a skeletally immature patient. The patient’s mother provided written informed consent for print and electronic publication of this case report.

Case Report

A 12-year-old boy was brought to our level I trauma center by ambulance after being hit by a car while riding a motorized scooter. He presented with a grade IIIB open tibial fracture and a distal fibula fracture of his left lower extremity and was taken to the operating room that night for irrigation and débridement, percutaneous fixation of the fibula, and intramedullary flexible nail fixation of the tibia. On postoperative day 1, he had increasing pain and, once his splint was removed, his compartments were found to be very tense. He was taken emergently to the operating room for 4 compartment fasciotomies of the left lower extremity with wound vacuum-assisted closure (VAC) placement. This was changed on hospital day 4 and was removed with definitive closure on day 7. Examination under anesthesia prior to the final wound VAC change was performed given the patient’s complaints during physical therapy. This showed anterior and posterior ligamentous instability of the knee, and he was placed in a knee immobilizer. He was discharged on hospital day 11.

At 2-week follow-up, the patient was doing well, except that he was nonadherent with the knee immobilizer and unable to fully extend his left knee. On examination, a posterior drawer sign was noted; therefore, the patient was referred for magnetic resonance imaging (MRI) to evaluate his ligaments. His MRI, 9 weeks after injury, showed: (1) complete tears of both the anterior and posterior cruciate ligaments (PCLs) (Figures 1A, 1B); (2) medial meniscus and lateral meniscus tears; (3) 2.0-cm plate-like avulsion fracture of the posterolateral femoral metaphysis involving the insertion of the lateral head of the gastrocnemius muscle, fibular collateral ligament, and popliteus muscle (Figure 2); and (4) left posterior lateral tibial plateau contusion.

The patient was started on a 6-week course of physical therapy with active and active-assisted extension exercises. At follow-up approximately 3½ months after injury, he was found to have a 35º flexion contracture with pain at the end extension. Unfortunately, his tibial fracture showed minimal signs of healing, and the decision was made to delay surgical intervention on the knee until the tibial fracture had healed. He was given a knee orthotic to wear at night to help regain his knee extension.

Six months after injury, the patient underwent open removal of the avulsed bony fragment, posterior knee capsule release, and autograft of the delayed union tibial fracture. He was placed in a straight leg cast postoperatively and was discharged home on postoperative day 2. He transitioned to a knee immobilizer after 2 weeks. Six weeks after the last surgery, he had range of motion of 0º to 130º. Ligamentous examination at this time showed anterior and posterior drawer signs, positive Lachman test, and dial test with 90º of external rotation. He was placed in physical therapy for a total of 10 weeks to work on his quadriceps muscle strength and 15º extension lag.

On 13-month postinjury radiographs, the patient was noted to have adequate healing of his tibial fracture, and ligamentous reconstruction was discussed. At this time, the patient did not have any instability or pain in the knee. Examination demonstrated a very mild effusion of the left knee. Range of motion determined by goniometer was from -3º to 140º, and Lachman test was positive but with solid 2+ endpoint. He also had a positive posterior drawer sign with no endpoint, positive sag sign of his tibia, and positive active quadriceps test of the left leg. His dial test showed some increased external rotation at 90º but was equivocal at 30º when compared with the contralateral knee, demonstrating involvement of the posterolateral corner.

Sixteen months after injury, repeat MRI to further evaluate the posterolateral corner showed: (1) complete medial and lateral meniscal healing without evidence of residual or recurrent tear, and (2) interval healing of the remote ACL and PCL tears with intact insertions (Figures 3A, 3B). This scan showed an end-to-end continuous ACL with homogeneous signal and disappearance of the secondary signs. Physical examination at this time showed a very firm endpoint on Lachman test but some laxity with his posterior drawer. Given these findings, the patient was given a brace and continued in physical therapy to strengthen his quadriceps muscle. By 20 months after injury, he had returned to competitive hockey and had no complaints of pain or instability. His physical examination showed full range of motion in a ligamentously stable knee with firm endpoint. The patient’s condition was unchanged at 29-month follow-up.

Discussion

There is a body of evidence that states a completely ruptured ACL does not heal.^3,6,10 In animal models, the ACL has been shown to have poor healing potential.^3,11 Some studies have suggested this is secondary to poor blood supply. Blood supply to the ACL is derived from a periligamentous, then endoligamentous, arterial network with a less vascularized area in the middle third of the ACL. Additionally, there is no blood supply from the tibia or femur, meaning the areas of attachment of the ligament are poorly vascularized.¹² With a minimal blood supply to the ACL, the supply of undifferentiated mesenchymal cells from the surrounding tissue during the initial healing process is limited. In vitro cell cultures of these cells have showed a reduced potential for proliferation and migration.⁹ Cells of the ACL have a lower response to growth factors than human medial collateral ligament cells, further suggesting a decreased reparative capacity.⁷ Joint fluid has been shown to inhibit the proliferation of these cells, further reducing their regenerative potential.¹³ Additionally, biomechanical factors that alter signaling pathways, sites of ligament reattachment, and injury to proprioceptive structures have been shown to negatively influence the healing response.^14-18

Review of the literature on healing of ACLs includes 2 case reports, totaling 3 patients, and 3 level IV therapeutic studies involving 74 patients total.^10,19-22 In most cases, the authors of these studies have indicated a nonoperative treatment protocol with bracing and a specific rehabilitation program. Malanga and colleagues¹⁰ demonstrated that an ACL torn from its attachment on the femur, with the majority of the ligament in good condition and no compromise in the length, healed back onto the femur. Kurosaka and coauthors²⁰ described case reports of isolated distal or proximal midsubstance tears that have healed spontaneously. However, none of the patients described in the literature were under the age of 20 years.

Treatment for pediatric patients with open physes causes some debate. Nonoperative management of ACL deficiency in adolescents is generally not recommended because the continued instability of the joint leads to intra-articular injury, functional impairment, and joint degeneration.^23-25 A recent systematic review found only 1 study that showed no increase in secondary intra-articular injury when surgery was delayed until skeletal maturity.²⁶ 

Our patient was a 12-year-old boy whose traumatic knee injury with multiple ruptured ligaments healed over the course of 20 months. It is likely that bracing associated with the patient’s second surgery and delayed union of his tibial fracture allowed healing tissue to be protected from excessive stress until it remodeled with sufficient strength. Most would assume that healing would occur early, during the first 6 to 9 months; however, our patient regained his stability between 8 and 13 months. It is possible that the hostile healing environment of the ACL, including the low blood supply, poor response to growth factors, and biomechanical environment, as described previously, played a factor in this delay.^7,9,12,13

It is important to recognize that our patient tore his ACL during a traumatic motorized scooter rollover collision, not the more common noncontact twisting injury. Additionally, given the patient’s knee surgery that was performed 6 months after the initial injury, it is possible that intra-articular scar formation contributed to his healing capacity. While this patient did not undergo arthroscopy to visualize the tear in the ACL, or its reconstitution, recent evidence suggests that the accuracy of MRI in diagnosing pediatric ACL injuries is excellent.^27,28 The diagnostic accuracy with new MRI machines has sensitivity and specificity approaching 100%.²⁹ Additionally, the patient’s subjective and objective improvements argue for a change in anatomy over a change in the quality of his examination.

Conclusion

The goal of ACL reconstruction in adolescents is to provide long-term stability to the knee while minimizing the risk of growth disturbance. This goal was achieved in our patient through the in situ healing of his ACL. Intrinsic reconstitution of a torn ACL is rare, and it is difficult to speculate which patients may have some healing potential. While this patient was an extreme example, his case demonstrated that protection of the knee from undue stress could favorably alter the environment of the knee to allow for healing of ACL tears. Such information could be valuable in managing select pediatric patients with open physes and ACL injuries nonoperatively, sparing them from the risks associated with surgical treatment. While we do not recommend nonoperative treatment for patients with acute tears of the ACL, we believe more investigation into the healing potential of the ACL, and potential pathways to augment this, is warranted.

The anterior cruciate ligament (ACL) restrains anterior translation of the tibia on the femur and controls rotation of the knee. The natural primary healing potential of the ACL has been extremely poor in clinical and experimental studies, and primary suture repair has not provided stability to the joint in most patients.^1-8 This has led surgeons to reconstruct the ACL, rather than to attempt nonoperative treatment. Anterior cruciate ligament reconstruction is recommended to help patients maintain activities that place shear and torque forces on the knee or to ameliorate persistent pain due to instability.⁹ Reconstruction of the ACL in adults is one of the most common procedures performed by orthopedic surgeons. However, reconstruction in the ACL-deficient adolescent remains a controversial subject, with debates surrounding operative timing and surgical technique.

This case report presents a skeletally immature patient who suffered a complete traumatic rupture of his ACL, which intrinsically healed. The patient had a protracted treatment course, complicated by an open tibial fracture with delayed union. He responded to a progressive rehabilitation program and has made a good functional recovery. Review of the literature has demonstrated limited evidence of intrinsic ACL healing, none of which has been shown to occur in a skeletally immature patient. The patient’s mother provided written informed consent for print and electronic publication of this case report.

Case Report

A 12-year-old boy was brought to our level I trauma center by ambulance after being hit by a car while riding a motorized scooter. He presented with a grade IIIB open tibial fracture and a distal fibula fracture of his left lower extremity and was taken to the operating room that night for irrigation and débridement, percutaneous fixation of the fibula, and intramedullary flexible nail fixation of the tibia. On postoperative day 1, he had increasing pain and, once his splint was removed, his compartments were found to be very tense. He was taken emergently to the operating room for 4 compartment fasciotomies of the left lower extremity with wound vacuum-assisted closure (VAC) placement. This was changed on hospital day 4 and was removed with definitive closure on day 7. Examination under anesthesia prior to the final wound VAC change was performed given the patient’s complaints during physical therapy. This showed anterior and posterior ligamentous instability of the knee, and he was placed in a knee immobilizer. He was discharged on hospital day 11.

At 2-week follow-up, the patient was doing well, except that he was nonadherent with the knee immobilizer and unable to fully extend his left knee. On examination, a posterior drawer sign was noted; therefore, the patient was referred for magnetic resonance imaging (MRI) to evaluate his ligaments. His MRI, 9 weeks after injury, showed: (1) complete tears of both the anterior and posterior cruciate ligaments (PCLs) (Figures 1A, 1B); (2) medial meniscus and lateral meniscus tears; (3) 2.0-cm plate-like avulsion fracture of the posterolateral femoral metaphysis involving the insertion of the lateral head of the gastrocnemius muscle, fibular collateral ligament, and popliteus muscle (Figure 2); and (4) left posterior lateral tibial plateau contusion.

The patient was started on a 6-week course of physical therapy with active and active-assisted extension exercises. At follow-up approximately 3½ months after injury, he was found to have a 35º flexion contracture with pain at the end extension. Unfortunately, his tibial fracture showed minimal signs of healing, and the decision was made to delay surgical intervention on the knee until the tibial fracture had healed. He was given a knee orthotic to wear at night to help regain his knee extension.

Six months after injury, the patient underwent open removal of the avulsed bony fragment, posterior knee capsule release, and autograft of the delayed union tibial fracture. He was placed in a straight leg cast postoperatively and was discharged home on postoperative day 2. He transitioned to a knee immobilizer after 2 weeks. Six weeks after the last surgery, he had range of motion of 0º to 130º. Ligamentous examination at this time showed anterior and posterior drawer signs, positive Lachman test, and dial test with 90º of external rotation. He was placed in physical therapy for a total of 10 weeks to work on his quadriceps muscle strength and 15º extension lag.

On 13-month postinjury radiographs, the patient was noted to have adequate healing of his tibial fracture, and ligamentous reconstruction was discussed. At this time, the patient did not have any instability or pain in the knee. Examination demonstrated a very mild effusion of the left knee. Range of motion determined by goniometer was from -3º to 140º, and Lachman test was positive but with solid 2+ endpoint. He also had a positive posterior drawer sign with no endpoint, positive sag sign of his tibia, and positive active quadriceps test of the left leg. His dial test showed some increased external rotation at 90º but was equivocal at 30º when compared with the contralateral knee, demonstrating involvement of the posterolateral corner.

Sixteen months after injury, repeat MRI to further evaluate the posterolateral corner showed: (1) complete medial and lateral meniscal healing without evidence of residual or recurrent tear, and (2) interval healing of the remote ACL and PCL tears with intact insertions (Figures 3A, 3B). This scan showed an end-to-end continuous ACL with homogeneous signal and disappearance of the secondary signs. Physical examination at this time showed a very firm endpoint on Lachman test but some laxity with his posterior drawer. Given these findings, the patient was given a brace and continued in physical therapy to strengthen his quadriceps muscle. By 20 months after injury, he had returned to competitive hockey and had no complaints of pain or instability. His physical examination showed full range of motion in a ligamentously stable knee with firm endpoint. The patient’s condition was unchanged at 29-month follow-up.

Discussion

There is a body of evidence that states a completely ruptured ACL does not heal.^3,6,10 In animal models, the ACL has been shown to have poor healing potential.^3,11 Some studies have suggested this is secondary to poor blood supply. Blood supply to the ACL is derived from a periligamentous, then endoligamentous, arterial network with a less vascularized area in the middle third of the ACL. Additionally, there is no blood supply from the tibia or femur, meaning the areas of attachment of the ligament are poorly vascularized.¹² With a minimal blood supply to the ACL, the supply of undifferentiated mesenchymal cells from the surrounding tissue during the initial healing process is limited. In vitro cell cultures of these cells have showed a reduced potential for proliferation and migration.⁹ Cells of the ACL have a lower response to growth factors than human medial collateral ligament cells, further suggesting a decreased reparative capacity.⁷ Joint fluid has been shown to inhibit the proliferation of these cells, further reducing their regenerative potential.¹³ Additionally, biomechanical factors that alter signaling pathways, sites of ligament reattachment, and injury to proprioceptive structures have been shown to negatively influence the healing response.^14-18

Review of the literature on healing of ACLs includes 2 case reports, totaling 3 patients, and 3 level IV therapeutic studies involving 74 patients total.^10,19-22 In most cases, the authors of these studies have indicated a nonoperative treatment protocol with bracing and a specific rehabilitation program. Malanga and colleagues¹⁰ demonstrated that an ACL torn from its attachment on the femur, with the majority of the ligament in good condition and no compromise in the length, healed back onto the femur. Kurosaka and coauthors²⁰ described case reports of isolated distal or proximal midsubstance tears that have healed spontaneously. However, none of the patients described in the literature were under the age of 20 years.

Treatment for pediatric patients with open physes causes some debate. Nonoperative management of ACL deficiency in adolescents is generally not recommended because the continued instability of the joint leads to intra-articular injury, functional impairment, and joint degeneration.^23-25 A recent systematic review found only 1 study that showed no increase in secondary intra-articular injury when surgery was delayed until skeletal maturity.²⁶ 

Our patient was a 12-year-old boy whose traumatic knee injury with multiple ruptured ligaments healed over the course of 20 months. It is likely that bracing associated with the patient’s second surgery and delayed union of his tibial fracture allowed healing tissue to be protected from excessive stress until it remodeled with sufficient strength. Most would assume that healing would occur early, during the first 6 to 9 months; however, our patient regained his stability between 8 and 13 months. It is possible that the hostile healing environment of the ACL, including the low blood supply, poor response to growth factors, and biomechanical environment, as described previously, played a factor in this delay.^7,9,12,13

It is important to recognize that our patient tore his ACL during a traumatic motorized scooter rollover collision, not the more common noncontact twisting injury. Additionally, given the patient’s knee surgery that was performed 6 months after the initial injury, it is possible that intra-articular scar formation contributed to his healing capacity. While this patient did not undergo arthroscopy to visualize the tear in the ACL, or its reconstitution, recent evidence suggests that the accuracy of MRI in diagnosing pediatric ACL injuries is excellent.^27,28 The diagnostic accuracy with new MRI machines has sensitivity and specificity approaching 100%.²⁹ Additionally, the patient’s subjective and objective improvements argue for a change in anatomy over a change in the quality of his examination.

Conclusion

The goal of ACL reconstruction in adolescents is to provide long-term stability to the knee while minimizing the risk of growth disturbance. This goal was achieved in our patient through the in situ healing of his ACL. Intrinsic reconstitution of a torn ACL is rare, and it is difficult to speculate which patients may have some healing potential. While this patient was an extreme example, his case demonstrated that protection of the knee from undue stress could favorably alter the environment of the knee to allow for healing of ACL tears. Such information could be valuable in managing select pediatric patients with open physes and ACL injuries nonoperatively, sparing them from the risks associated with surgical treatment. While we do not recommend nonoperative treatment for patients with acute tears of the ACL, we believe more investigation into the healing potential of the ACL, and potential pathways to augment this, is warranted.

The anterior cruciate ligament (ACL) restrains anterior translation of the tibia on the femur and controls rotation of the knee. The natural primary healing potential of the ACL has been extremely poor in clinical and experimental studies, and primary suture repair has not provided stability to the joint in most patients.^1-8 This has led surgeons to reconstruct the ACL, rather than to attempt nonoperative treatment. Anterior cruciate ligament reconstruction is recommended to help patients maintain activities that place shear and torque forces on the knee or to ameliorate persistent pain due to instability.⁹ Reconstruction of the ACL in adults is one of the most common procedures performed by orthopedic surgeons. However, reconstruction in the ACL-deficient adolescent remains a controversial subject, with debates surrounding operative timing and surgical technique.

This case report presents a skeletally immature patient who suffered a complete traumatic rupture of his ACL, which intrinsically healed. The patient had a protracted treatment course, complicated by an open tibial fracture with delayed union. He responded to a progressive rehabilitation program and has made a good functional recovery. Review of the literature has demonstrated limited evidence of intrinsic ACL healing, none of which has been shown to occur in a skeletally immature patient. The patient’s mother provided written informed consent for print and electronic publication of this case report.

Case Report

A 12-year-old boy was brought to our level I trauma center by ambulance after being hit by a car while riding a motorized scooter. He presented with a grade IIIB open tibial fracture and a distal fibula fracture of his left lower extremity and was taken to the operating room that night for irrigation and débridement, percutaneous fixation of the fibula, and intramedullary flexible nail fixation of the tibia. On postoperative day 1, he had increasing pain and, once his splint was removed, his compartments were found to be very tense. He was taken emergently to the operating room for 4 compartment fasciotomies of the left lower extremity with wound vacuum-assisted closure (VAC) placement. This was changed on hospital day 4 and was removed with definitive closure on day 7. Examination under anesthesia prior to the final wound VAC change was performed given the patient’s complaints during physical therapy. This showed anterior and posterior ligamentous instability of the knee, and he was placed in a knee immobilizer. He was discharged on hospital day 11.

At 2-week follow-up, the patient was doing well, except that he was nonadherent with the knee immobilizer and unable to fully extend his left knee. On examination, a posterior drawer sign was noted; therefore, the patient was referred for magnetic resonance imaging (MRI) to evaluate his ligaments. His MRI, 9 weeks after injury, showed: (1) complete tears of both the anterior and posterior cruciate ligaments (PCLs) (Figures 1A, 1B); (2) medial meniscus and lateral meniscus tears; (3) 2.0-cm plate-like avulsion fracture of the posterolateral femoral metaphysis involving the insertion of the lateral head of the gastrocnemius muscle, fibular collateral ligament, and popliteus muscle (Figure 2); and (4) left posterior lateral tibial plateau contusion.

The patient was started on a 6-week course of physical therapy with active and active-assisted extension exercises. At follow-up approximately 3½ months after injury, he was found to have a 35º flexion contracture with pain at the end extension. Unfortunately, his tibial fracture showed minimal signs of healing, and the decision was made to delay surgical intervention on the knee until the tibial fracture had healed. He was given a knee orthotic to wear at night to help regain his knee extension.

Six months after injury, the patient underwent open removal of the avulsed bony fragment, posterior knee capsule release, and autograft of the delayed union tibial fracture. He was placed in a straight leg cast postoperatively and was discharged home on postoperative day 2. He transitioned to a knee immobilizer after 2 weeks. Six weeks after the last surgery, he had range of motion of 0º to 130º. Ligamentous examination at this time showed anterior and posterior drawer signs, positive Lachman test, and dial test with 90º of external rotation. He was placed in physical therapy for a total of 10 weeks to work on his quadriceps muscle strength and 15º extension lag.

On 13-month postinjury radiographs, the patient was noted to have adequate healing of his tibial fracture, and ligamentous reconstruction was discussed. At this time, the patient did not have any instability or pain in the knee. Examination demonstrated a very mild effusion of the left knee. Range of motion determined by goniometer was from -3º to 140º, and Lachman test was positive but with solid 2+ endpoint. He also had a positive posterior drawer sign with no endpoint, positive sag sign of his tibia, and positive active quadriceps test of the left leg. His dial test showed some increased external rotation at 90º but was equivocal at 30º when compared with the contralateral knee, demonstrating involvement of the posterolateral corner.

Sixteen months after injury, repeat MRI to further evaluate the posterolateral corner showed: (1) complete medial and lateral meniscal healing without evidence of residual or recurrent tear, and (2) interval healing of the remote ACL and PCL tears with intact insertions (Figures 3A, 3B). This scan showed an end-to-end continuous ACL with homogeneous signal and disappearance of the secondary signs. Physical examination at this time showed a very firm endpoint on Lachman test but some laxity with his posterior drawer. Given these findings, the patient was given a brace and continued in physical therapy to strengthen his quadriceps muscle. By 20 months after injury, he had returned to competitive hockey and had no complaints of pain or instability. His physical examination showed full range of motion in a ligamentously stable knee with firm endpoint. The patient’s condition was unchanged at 29-month follow-up.

Discussion

There is a body of evidence that states a completely ruptured ACL does not heal.^3,6,10 In animal models, the ACL has been shown to have poor healing potential.^3,11 Some studies have suggested this is secondary to poor blood supply. Blood supply to the ACL is derived from a periligamentous, then endoligamentous, arterial network with a less vascularized area in the middle third of the ACL. Additionally, there is no blood supply from the tibia or femur, meaning the areas of attachment of the ligament are poorly vascularized.¹² With a minimal blood supply to the ACL, the supply of undifferentiated mesenchymal cells from the surrounding tissue during the initial healing process is limited. In vitro cell cultures of these cells have showed a reduced potential for proliferation and migration.⁹ Cells of the ACL have a lower response to growth factors than human medial collateral ligament cells, further suggesting a decreased reparative capacity.⁷ Joint fluid has been shown to inhibit the proliferation of these cells, further reducing their regenerative potential.¹³ Additionally, biomechanical factors that alter signaling pathways, sites of ligament reattachment, and injury to proprioceptive structures have been shown to negatively influence the healing response.^14-18

Review of the literature on healing of ACLs includes 2 case reports, totaling 3 patients, and 3 level IV therapeutic studies involving 74 patients total.^10,19-22 In most cases, the authors of these studies have indicated a nonoperative treatment protocol with bracing and a specific rehabilitation program. Malanga and colleagues¹⁰ demonstrated that an ACL torn from its attachment on the femur, with the majority of the ligament in good condition and no compromise in the length, healed back onto the femur. Kurosaka and coauthors²⁰ described case reports of isolated distal or proximal midsubstance tears that have healed spontaneously. However, none of the patients described in the literature were under the age of 20 years.

Treatment for pediatric patients with open physes causes some debate. Nonoperative management of ACL deficiency in adolescents is generally not recommended because the continued instability of the joint leads to intra-articular injury, functional impairment, and joint degeneration.^23-25 A recent systematic review found only 1 study that showed no increase in secondary intra-articular injury when surgery was delayed until skeletal maturity.²⁶ 

Our patient was a 12-year-old boy whose traumatic knee injury with multiple ruptured ligaments healed over the course of 20 months. It is likely that bracing associated with the patient’s second surgery and delayed union of his tibial fracture allowed healing tissue to be protected from excessive stress until it remodeled with sufficient strength. Most would assume that healing would occur early, during the first 6 to 9 months; however, our patient regained his stability between 8 and 13 months. It is possible that the hostile healing environment of the ACL, including the low blood supply, poor response to growth factors, and biomechanical environment, as described previously, played a factor in this delay.^7,9,12,13

It is important to recognize that our patient tore his ACL during a traumatic motorized scooter rollover collision, not the more common noncontact twisting injury. Additionally, given the patient’s knee surgery that was performed 6 months after the initial injury, it is possible that intra-articular scar formation contributed to his healing capacity. While this patient did not undergo arthroscopy to visualize the tear in the ACL, or its reconstitution, recent evidence suggests that the accuracy of MRI in diagnosing pediatric ACL injuries is excellent.^27,28 The diagnostic accuracy with new MRI machines has sensitivity and specificity approaching 100%.²⁹ Additionally, the patient’s subjective and objective improvements argue for a change in anatomy over a change in the quality of his examination.

Conclusion

The goal of ACL reconstruction in adolescents is to provide long-term stability to the knee while minimizing the risk of growth disturbance. This goal was achieved in our patient through the in situ healing of his ACL. Intrinsic reconstitution of a torn ACL is rare, and it is difficult to speculate which patients may have some healing potential. While this patient was an extreme example, his case demonstrated that protection of the knee from undue stress could favorably alter the environment of the knee to allow for healing of ACL tears. Such information could be valuable in managing select pediatric patients with open physes and ACL injuries nonoperatively, sparing them from the risks associated with surgical treatment. While we do not recommend nonoperative treatment for patients with acute tears of the ACL, we believe more investigation into the healing potential of the ACL, and potential pathways to augment this, is warranted.

Fracture blisters are a relatively uncommon complication of high-energy fractures, with an incidence of 2.9%.¹ In the lower extremity, fracture blisters almost always occur distal to the knee.¹ Histologically, the blisters represent an injury to the dermoepidermal junction.² On physical examination, there are tense blood- and/or clear fluid–filled bullae overlying markedly swollen and edematous soft tissue,¹ resembling a second-degree burn.³ Infection may develop after fracture blisters,¹ and this is perhaps the most dreaded complication of total knee arthroplasty (TKA). The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 71-year-old man with end-stage osteoarthritis of the right knee underwent an elective TKA with cemented components (Legion PS; Smith & Nephew). His medical history included venous insufficiency, type 2 diabetes mellitus, chronic obstructive sleep apnea, hypertension, morbid obesity (body mass index, 50), and a previous uneventful left TKA. Tourniquet time was 78 minutes and estimated blood loss was 100 mL. An intra-articular drain was used and was removed on the first postoperative day. After wound closure, a soft splint bandage consisting of 2 to 3 layers of cotton and bias wrap was applied. Deep vein thrombosis (DVT) prophylaxis with enoxaparin 40 mg once daily was started on the first postoperative day.

Upon removal of the surgical dressings on the second postoperative day, the anterior leg was found to have a combination of tense clear fluid– and blood-filled blisters on markedly swollen and erythematous skin. The incision was minimally involved (Figure A). There was diffuse 2+ pitting edema with hyperesthesia in the affected skin distal to the knee. Prior to these findings, the patient had complained of increasing pain in his operative leg, but there was no escalation in analgesic requirements. There was no evidence of compartment syndrome on serial examinations. An ultrasound of the lower extremity was negative for DVT. Plain films did not show iatrogenic fractures. There was no intraoperative vascular injury, and the foot pulses remained unchanged between the time the patient was in the preoperative holding unit, the postanesthesia care unit, and the orthopedic ward. The operative leg was treated with elevation and loosely applied Kerlix roll gauze (Kendall, Covidien), but active blister formation continued for another 2 days. A 10-day prophylactic course of trimethoprim/sulfamethoxazole was initiated on the third postoperative day after the blisters started to rupture. The patient was allowed to bear weight as tolerated, but his physical therapy (PT) course was limited by pain and fear “of losing his leg.” He declined several PT sessions and was hesitant to use continuous passive motion. The patient was discharged to a short-term rehabilitation facility with weekly outpatient follow-up. On the second postoperative week, his fluid-filled blisters completely reepithelialized, but the blood-filled blisters required an additional week for reepithelialization (Figure B). While the patient’s knee was stiff because of limited PT participation, it was not until the second postoperative week when most of the fracture blisters had healed that he was able to resume an intensive knee exercise program, avoiding the need for manipulation under anesthesia.

Discussion

Giordano and colleagues² identified 2 types of fracture blisters: clear fluid– and blood-filled. While both types involved disruption of the dermoepidermal junction, greater disruption and complete absence of dermal epithelial cells was observed in the hemorrhagic type. Clinical follow-up of the patients in the study by Giordano and colleagues² showed that the mean time for reepithelialization was 12 days for fluid-filled blisters and 16 days for blood-filled blisters. These findings are similar to what we observed in our case report. In particular, the fluid-filled blisters healed in 2 weeks, whereas the blood-filled blisters required 3 weeks to heal.

The etiology of the fracture blisters in this patient is likely multifactorial and related to age, obesity, venous insufficiency, and diabetes mellitus. Farage and colleagues⁴ described a series of progressive degenerative changes in the aging skin, including vascular atrophy and degradation of dermal connective tissue, leading to compromised skin competence. The integrity of the dermis can be further reduced in patients with diabetes through glycosylation of collagen fibrils.⁵ Compared with age-matched normal controls, patients with insulin-dependent diabetes have a reduced threshold to suction-induced blister formation.⁶ Obesity is another potential contributing factor, with multiple studies showing significantly impaired venous flow in obese patients.^7,8 Taken together, soft-tissue swelling after surgery in the setting of chronic venous insufficiency and compromised skin due to advanced age and diabetes may lead to markedly elevated interstitial pressure. One mechanism to relieve such abnormally high pressure is the formation of fracture blisters.¹

Surgical risk factors that could have contributed to the complication in this case include the surgical skin preparation solution (ChloraPrep; CareFusion), use of adhesive antimicrobial drape (Ioban, 3M), tourniquet time, dressing choice, and DVT prophylaxis regimen. While the skin preparation solution is an unlikely culprit since the presentation is not consistent with contact dermatitis, inappropriate strapping or removal of the adhesive drape could result in stretch injury of the skin, shearing the dermoepidermal junction and causing tension blisters.⁹ There were no intraoperative complications and the tourniquet time was appropriate (78 minutes). Postoperatively, no compressive or adhesive dressings were used. With regards to DVT prophylaxis, the patient received a single dose of enoxaparin on the first postoperative day. While heparin-induced hemorrhagic blisters have been reported,¹⁰ I do not feel that the use of enoxaparin was a contributing factor. Heparin-induced blisters have been described as systemic blisters,¹⁰ whereas the blisters in this case were confined to the operative extremity. The patient was not taking any nutritional supplements (eg, fish oil, vitamin E) that could have increased his risk of bleeding. Throughout his hospital stay, he was hemodynamically stable and did not require blood transfusion.

Management of fracture blisters is controversial, and there is no consensus on appropriate soft-tissue handling. In this patient, the blisters were left intact. Blister fluid has been shown to be sterile, containing growth factors, opsonins, and activated neutrophils that aid in healing and infection prevention.¹ Giordano and Koval¹¹ found no difference in the outcome of 3 soft-tissue treatment techniques: (1) aspiration of the blister, (2) deroofing of the blister followed by application of a topical antibiotic cream or coverage with nonadherent dressing, or (3) keeping the blister intact and covered with loose dressing or exposed to air. In contrast, Strauss and colleagues¹² found that deroofing the fracture blister to healthy tissue followed by twice-daily application of silver sulfadiazine antibiotic cream promoted reepithelialization and resulted in better cosmetic appearance and higher patient satisfaction. 

The optimal dressing for fracture blisters remains elusive. Madden and colleagues¹³ showed that the use of occlusive nonadherent dressing was associated with significantly faster healing and less pain compared with semiocclusive, antibiotic-impregnated dressings. In another study, Varela and colleagues¹ found no differences in blister healing between patients treated with either (1) dry dressing and casting, (2) Silvadene dressing (King Pharmaceuticals), or (3) whirlpool débridement and Silvadene dressing.

Infection is perhaps the most dreaded complication of fracture blisters after TKA. Varela and colleagues¹ showed that, while the fluid in intact blisters was a sterile transudate, polymicrobial colonization with skin flora often occurred soon after blister rupture and persisted until reepithelialization. Our patient received a 10-day course of prophylactic antibiotics and no superficial or deep infection developed; however, the real contribution of antibiotic prophylaxis to the absence of infection cannot be established based solely on 1 case.

Pain is another concern associated with fracture blisters. Our patient had significant pain that limited his ability to participate in PT, resulting in limited knee range of motion and eventual discharge to a short-term rehabilitation facility. Fortunately, after resolution of the fracture blisters, he was able to participate in an aggressive rehabilitation program. By 6 weeks after surgery, he had significant improvement in his knee motion, avoiding the need for manipulation under anesthesia.

Conclusion

This case represents the first reported fracture blisters after primary TKA. The risk of deep surgical site infection, a devastating complication after TKA, is perhaps the most frightening concern of this rare complication. While the etiology and the management are controversial, there is evidence to recommend prophylactic antibiotics after blister rupture and skin desquamation. The decision to withhold DVT prophylaxis should be based on individual patient risk factors and blister type (blood-filled vs clear fluid–filled). Patients should be encouraged to continue knee exercises during reepithelialization to avoid stiffness.

Fracture blisters are a relatively uncommon complication of high-energy fractures, with an incidence of 2.9%.¹ In the lower extremity, fracture blisters almost always occur distal to the knee.¹ Histologically, the blisters represent an injury to the dermoepidermal junction.² On physical examination, there are tense blood- and/or clear fluid–filled bullae overlying markedly swollen and edematous soft tissue,¹ resembling a second-degree burn.³ Infection may develop after fracture blisters,¹ and this is perhaps the most dreaded complication of total knee arthroplasty (TKA). The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 71-year-old man with end-stage osteoarthritis of the right knee underwent an elective TKA with cemented components (Legion PS; Smith & Nephew). His medical history included venous insufficiency, type 2 diabetes mellitus, chronic obstructive sleep apnea, hypertension, morbid obesity (body mass index, 50), and a previous uneventful left TKA. Tourniquet time was 78 minutes and estimated blood loss was 100 mL. An intra-articular drain was used and was removed on the first postoperative day. After wound closure, a soft splint bandage consisting of 2 to 3 layers of cotton and bias wrap was applied. Deep vein thrombosis (DVT) prophylaxis with enoxaparin 40 mg once daily was started on the first postoperative day.

Upon removal of the surgical dressings on the second postoperative day, the anterior leg was found to have a combination of tense clear fluid– and blood-filled blisters on markedly swollen and erythematous skin. The incision was minimally involved (Figure A). There was diffuse 2+ pitting edema with hyperesthesia in the affected skin distal to the knee. Prior to these findings, the patient had complained of increasing pain in his operative leg, but there was no escalation in analgesic requirements. There was no evidence of compartment syndrome on serial examinations. An ultrasound of the lower extremity was negative for DVT. Plain films did not show iatrogenic fractures. There was no intraoperative vascular injury, and the foot pulses remained unchanged between the time the patient was in the preoperative holding unit, the postanesthesia care unit, and the orthopedic ward. The operative leg was treated with elevation and loosely applied Kerlix roll gauze (Kendall, Covidien), but active blister formation continued for another 2 days. A 10-day prophylactic course of trimethoprim/sulfamethoxazole was initiated on the third postoperative day after the blisters started to rupture. The patient was allowed to bear weight as tolerated, but his physical therapy (PT) course was limited by pain and fear “of losing his leg.” He declined several PT sessions and was hesitant to use continuous passive motion. The patient was discharged to a short-term rehabilitation facility with weekly outpatient follow-up. On the second postoperative week, his fluid-filled blisters completely reepithelialized, but the blood-filled blisters required an additional week for reepithelialization (Figure B). While the patient’s knee was stiff because of limited PT participation, it was not until the second postoperative week when most of the fracture blisters had healed that he was able to resume an intensive knee exercise program, avoiding the need for manipulation under anesthesia.

Discussion

Giordano and colleagues² identified 2 types of fracture blisters: clear fluid– and blood-filled. While both types involved disruption of the dermoepidermal junction, greater disruption and complete absence of dermal epithelial cells was observed in the hemorrhagic type. Clinical follow-up of the patients in the study by Giordano and colleagues² showed that the mean time for reepithelialization was 12 days for fluid-filled blisters and 16 days for blood-filled blisters. These findings are similar to what we observed in our case report. In particular, the fluid-filled blisters healed in 2 weeks, whereas the blood-filled blisters required 3 weeks to heal.

The etiology of the fracture blisters in this patient is likely multifactorial and related to age, obesity, venous insufficiency, and diabetes mellitus. Farage and colleagues⁴ described a series of progressive degenerative changes in the aging skin, including vascular atrophy and degradation of dermal connective tissue, leading to compromised skin competence. The integrity of the dermis can be further reduced in patients with diabetes through glycosylation of collagen fibrils.⁵ Compared with age-matched normal controls, patients with insulin-dependent diabetes have a reduced threshold to suction-induced blister formation.⁶ Obesity is another potential contributing factor, with multiple studies showing significantly impaired venous flow in obese patients.^7,8 Taken together, soft-tissue swelling after surgery in the setting of chronic venous insufficiency and compromised skin due to advanced age and diabetes may lead to markedly elevated interstitial pressure. One mechanism to relieve such abnormally high pressure is the formation of fracture blisters.¹

Surgical risk factors that could have contributed to the complication in this case include the surgical skin preparation solution (ChloraPrep; CareFusion), use of adhesive antimicrobial drape (Ioban, 3M), tourniquet time, dressing choice, and DVT prophylaxis regimen. While the skin preparation solution is an unlikely culprit since the presentation is not consistent with contact dermatitis, inappropriate strapping or removal of the adhesive drape could result in stretch injury of the skin, shearing the dermoepidermal junction and causing tension blisters.⁹ There were no intraoperative complications and the tourniquet time was appropriate (78 minutes). Postoperatively, no compressive or adhesive dressings were used. With regards to DVT prophylaxis, the patient received a single dose of enoxaparin on the first postoperative day. While heparin-induced hemorrhagic blisters have been reported,¹⁰ I do not feel that the use of enoxaparin was a contributing factor. Heparin-induced blisters have been described as systemic blisters,¹⁰ whereas the blisters in this case were confined to the operative extremity. The patient was not taking any nutritional supplements (eg, fish oil, vitamin E) that could have increased his risk of bleeding. Throughout his hospital stay, he was hemodynamically stable and did not require blood transfusion.

Management of fracture blisters is controversial, and there is no consensus on appropriate soft-tissue handling. In this patient, the blisters were left intact. Blister fluid has been shown to be sterile, containing growth factors, opsonins, and activated neutrophils that aid in healing and infection prevention.¹ Giordano and Koval¹¹ found no difference in the outcome of 3 soft-tissue treatment techniques: (1) aspiration of the blister, (2) deroofing of the blister followed by application of a topical antibiotic cream or coverage with nonadherent dressing, or (3) keeping the blister intact and covered with loose dressing or exposed to air. In contrast, Strauss and colleagues¹² found that deroofing the fracture blister to healthy tissue followed by twice-daily application of silver sulfadiazine antibiotic cream promoted reepithelialization and resulted in better cosmetic appearance and higher patient satisfaction. 

The optimal dressing for fracture blisters remains elusive. Madden and colleagues¹³ showed that the use of occlusive nonadherent dressing was associated with significantly faster healing and less pain compared with semiocclusive, antibiotic-impregnated dressings. In another study, Varela and colleagues¹ found no differences in blister healing between patients treated with either (1) dry dressing and casting, (2) Silvadene dressing (King Pharmaceuticals), or (3) whirlpool débridement and Silvadene dressing.

Infection is perhaps the most dreaded complication of fracture blisters after TKA. Varela and colleagues¹ showed that, while the fluid in intact blisters was a sterile transudate, polymicrobial colonization with skin flora often occurred soon after blister rupture and persisted until reepithelialization. Our patient received a 10-day course of prophylactic antibiotics and no superficial or deep infection developed; however, the real contribution of antibiotic prophylaxis to the absence of infection cannot be established based solely on 1 case.

Pain is another concern associated with fracture blisters. Our patient had significant pain that limited his ability to participate in PT, resulting in limited knee range of motion and eventual discharge to a short-term rehabilitation facility. Fortunately, after resolution of the fracture blisters, he was able to participate in an aggressive rehabilitation program. By 6 weeks after surgery, he had significant improvement in his knee motion, avoiding the need for manipulation under anesthesia.

Conclusion

This case represents the first reported fracture blisters after primary TKA. The risk of deep surgical site infection, a devastating complication after TKA, is perhaps the most frightening concern of this rare complication. While the etiology and the management are controversial, there is evidence to recommend prophylactic antibiotics after blister rupture and skin desquamation. The decision to withhold DVT prophylaxis should be based on individual patient risk factors and blister type (blood-filled vs clear fluid–filled). Patients should be encouraged to continue knee exercises during reepithelialization to avoid stiffness.

Fracture blisters are a relatively uncommon complication of high-energy fractures, with an incidence of 2.9%.¹ In the lower extremity, fracture blisters almost always occur distal to the knee.¹ Histologically, the blisters represent an injury to the dermoepidermal junction.² On physical examination, there are tense blood- and/or clear fluid–filled bullae overlying markedly swollen and edematous soft tissue,¹ resembling a second-degree burn.³ Infection may develop after fracture blisters,¹ and this is perhaps the most dreaded complication of total knee arthroplasty (TKA). The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 71-year-old man with end-stage osteoarthritis of the right knee underwent an elective TKA with cemented components (Legion PS; Smith & Nephew). His medical history included venous insufficiency, type 2 diabetes mellitus, chronic obstructive sleep apnea, hypertension, morbid obesity (body mass index, 50), and a previous uneventful left TKA. Tourniquet time was 78 minutes and estimated blood loss was 100 mL. An intra-articular drain was used and was removed on the first postoperative day. After wound closure, a soft splint bandage consisting of 2 to 3 layers of cotton and bias wrap was applied. Deep vein thrombosis (DVT) prophylaxis with enoxaparin 40 mg once daily was started on the first postoperative day.

Upon removal of the surgical dressings on the second postoperative day, the anterior leg was found to have a combination of tense clear fluid– and blood-filled blisters on markedly swollen and erythematous skin. The incision was minimally involved (Figure A). There was diffuse 2+ pitting edema with hyperesthesia in the affected skin distal to the knee. Prior to these findings, the patient had complained of increasing pain in his operative leg, but there was no escalation in analgesic requirements. There was no evidence of compartment syndrome on serial examinations. An ultrasound of the lower extremity was negative for DVT. Plain films did not show iatrogenic fractures. There was no intraoperative vascular injury, and the foot pulses remained unchanged between the time the patient was in the preoperative holding unit, the postanesthesia care unit, and the orthopedic ward. The operative leg was treated with elevation and loosely applied Kerlix roll gauze (Kendall, Covidien), but active blister formation continued for another 2 days. A 10-day prophylactic course of trimethoprim/sulfamethoxazole was initiated on the third postoperative day after the blisters started to rupture. The patient was allowed to bear weight as tolerated, but his physical therapy (PT) course was limited by pain and fear “of losing his leg.” He declined several PT sessions and was hesitant to use continuous passive motion. The patient was discharged to a short-term rehabilitation facility with weekly outpatient follow-up. On the second postoperative week, his fluid-filled blisters completely reepithelialized, but the blood-filled blisters required an additional week for reepithelialization (Figure B). While the patient’s knee was stiff because of limited PT participation, it was not until the second postoperative week when most of the fracture blisters had healed that he was able to resume an intensive knee exercise program, avoiding the need for manipulation under anesthesia.

Discussion

Giordano and colleagues² identified 2 types of fracture blisters: clear fluid– and blood-filled. While both types involved disruption of the dermoepidermal junction, greater disruption and complete absence of dermal epithelial cells was observed in the hemorrhagic type. Clinical follow-up of the patients in the study by Giordano and colleagues² showed that the mean time for reepithelialization was 12 days for fluid-filled blisters and 16 days for blood-filled blisters. These findings are similar to what we observed in our case report. In particular, the fluid-filled blisters healed in 2 weeks, whereas the blood-filled blisters required 3 weeks to heal.

The etiology of the fracture blisters in this patient is likely multifactorial and related to age, obesity, venous insufficiency, and diabetes mellitus. Farage and colleagues⁴ described a series of progressive degenerative changes in the aging skin, including vascular atrophy and degradation of dermal connective tissue, leading to compromised skin competence. The integrity of the dermis can be further reduced in patients with diabetes through glycosylation of collagen fibrils.⁵ Compared with age-matched normal controls, patients with insulin-dependent diabetes have a reduced threshold to suction-induced blister formation.⁶ Obesity is another potential contributing factor, with multiple studies showing significantly impaired venous flow in obese patients.^7,8 Taken together, soft-tissue swelling after surgery in the setting of chronic venous insufficiency and compromised skin due to advanced age and diabetes may lead to markedly elevated interstitial pressure. One mechanism to relieve such abnormally high pressure is the formation of fracture blisters.¹

Surgical risk factors that could have contributed to the complication in this case include the surgical skin preparation solution (ChloraPrep; CareFusion), use of adhesive antimicrobial drape (Ioban, 3M), tourniquet time, dressing choice, and DVT prophylaxis regimen. While the skin preparation solution is an unlikely culprit since the presentation is not consistent with contact dermatitis, inappropriate strapping or removal of the adhesive drape could result in stretch injury of the skin, shearing the dermoepidermal junction and causing tension blisters.⁹ There were no intraoperative complications and the tourniquet time was appropriate (78 minutes). Postoperatively, no compressive or adhesive dressings were used. With regards to DVT prophylaxis, the patient received a single dose of enoxaparin on the first postoperative day. While heparin-induced hemorrhagic blisters have been reported,¹⁰ I do not feel that the use of enoxaparin was a contributing factor. Heparin-induced blisters have been described as systemic blisters,¹⁰ whereas the blisters in this case were confined to the operative extremity. The patient was not taking any nutritional supplements (eg, fish oil, vitamin E) that could have increased his risk of bleeding. Throughout his hospital stay, he was hemodynamically stable and did not require blood transfusion.

Management of fracture blisters is controversial, and there is no consensus on appropriate soft-tissue handling. In this patient, the blisters were left intact. Blister fluid has been shown to be sterile, containing growth factors, opsonins, and activated neutrophils that aid in healing and infection prevention.¹ Giordano and Koval¹¹ found no difference in the outcome of 3 soft-tissue treatment techniques: (1) aspiration of the blister, (2) deroofing of the blister followed by application of a topical antibiotic cream or coverage with nonadherent dressing, or (3) keeping the blister intact and covered with loose dressing or exposed to air. In contrast, Strauss and colleagues¹² found that deroofing the fracture blister to healthy tissue followed by twice-daily application of silver sulfadiazine antibiotic cream promoted reepithelialization and resulted in better cosmetic appearance and higher patient satisfaction. 

The optimal dressing for fracture blisters remains elusive. Madden and colleagues¹³ showed that the use of occlusive nonadherent dressing was associated with significantly faster healing and less pain compared with semiocclusive, antibiotic-impregnated dressings. In another study, Varela and colleagues¹ found no differences in blister healing between patients treated with either (1) dry dressing and casting, (2) Silvadene dressing (King Pharmaceuticals), or (3) whirlpool débridement and Silvadene dressing.

Infection is perhaps the most dreaded complication of fracture blisters after TKA. Varela and colleagues¹ showed that, while the fluid in intact blisters was a sterile transudate, polymicrobial colonization with skin flora often occurred soon after blister rupture and persisted until reepithelialization. Our patient received a 10-day course of prophylactic antibiotics and no superficial or deep infection developed; however, the real contribution of antibiotic prophylaxis to the absence of infection cannot be established based solely on 1 case.

Pain is another concern associated with fracture blisters. Our patient had significant pain that limited his ability to participate in PT, resulting in limited knee range of motion and eventual discharge to a short-term rehabilitation facility. Fortunately, after resolution of the fracture blisters, he was able to participate in an aggressive rehabilitation program. By 6 weeks after surgery, he had significant improvement in his knee motion, avoiding the need for manipulation under anesthesia.

Conclusion

This case represents the first reported fracture blisters after primary TKA. The risk of deep surgical site infection, a devastating complication after TKA, is perhaps the most frightening concern of this rare complication. While the etiology and the management are controversial, there is evidence to recommend prophylactic antibiotics after blister rupture and skin desquamation. The decision to withhold DVT prophylaxis should be based on individual patient risk factors and blister type (blood-filled vs clear fluid–filled). Patients should be encouraged to continue knee exercises during reepithelialization to avoid stiffness.