Imaging

NEW YORK – A study of an international database of individuals who have had open repair for acute type A aortic dissection (ATAAD) has revealed that in the past 20 years, cardiovascular surgeons have widely embraced valve-sparing procedures, bioprosthetic valves, and cerebral profusion strategies, according to a report here on the latest analysis of the database.

The most telling result is the decline in overall mortality, Santi Trimarchi, MD, PhD, of the University of Milan IRCCS Policlinico San Donato in Italy reported on behalf of the International Registry of Acute Aortic Dissection (IRAD) Interventional Cohort (IVC). The cohort analyzed surgery techniques and outcomes of 1,732 patients who had open repair from 1996 to 2016, clustering results in three time intervals: 1996-2003; 2004-2009; and 2010-2015.

“We noted in the registry that the overall in-hospital mortality rate was 14.3%, and this mortality decreased over time from 17.5% in the first six-year time span to 12.2% in the last six years,” Dr. Trimarchi said.

Among other trends the study identified are greater reliance on biological vs. mechanical valves, an increase in valve-sparing procedures, and steady use of Bentall procedures throughout the study period. “Operative techniques for redo aortic valve repair have been improving over the time, and that’s why we see more frequent use of biologic valves,” he said at the meeting, sponsored by the American Association for Thoracic Surgery.

“Cerebral profusion management has been widely adopted,” Dr. Trimarchi said. “Also there is an important trend showing an increasing utilization of antegrade cerebral profusion while we see a negative trend of the utilization of retrograde brain protection.”

Dr. Trimarchi attributed the detail the study generated to the survey form sent to the 26 IRAD-IVC sites around the world. The form measures 131 different variables, he said.

“Using this new specific surgical data form, we think we can address some surgical issues and report better data from the IRAD registry results on acute dissection,” he said. “These analyses have shown there have been significant changes in operative strategy over time in terms of managing such patients, and more importantly, a significant decrease in in-hospital mortality was observed in a 20-year time period.”

Dr. Trimarchi disclosed that he has received speaking and consulting fees and research support from W.L. Gore & Associates and Medtronic. IRAD is supported by W.L. Gore, Active Sites, Medtronic, Varbedian Aortic Research Fund, the Hewlett Foundation, the Mardigian Foundation, UM Faculty Group Practice, Terumo, and Ann and Bob Aikens.

NEW YORK – A study of an international database of individuals who have had open repair for acute type A aortic dissection (ATAAD) has revealed that in the past 20 years, cardiovascular surgeons have widely embraced valve-sparing procedures, bioprosthetic valves, and cerebral profusion strategies, according to a report here on the latest analysis of the database.

The most telling result is the decline in overall mortality, Santi Trimarchi, MD, PhD, of the University of Milan IRCCS Policlinico San Donato in Italy reported on behalf of the International Registry of Acute Aortic Dissection (IRAD) Interventional Cohort (IVC). The cohort analyzed surgery techniques and outcomes of 1,732 patients who had open repair from 1996 to 2016, clustering results in three time intervals: 1996-2003; 2004-2009; and 2010-2015.

“We noted in the registry that the overall in-hospital mortality rate was 14.3%, and this mortality decreased over time from 17.5% in the first six-year time span to 12.2% in the last six years,” Dr. Trimarchi said.

Among other trends the study identified are greater reliance on biological vs. mechanical valves, an increase in valve-sparing procedures, and steady use of Bentall procedures throughout the study period. “Operative techniques for redo aortic valve repair have been improving over the time, and that’s why we see more frequent use of biologic valves,” he said at the meeting, sponsored by the American Association for Thoracic Surgery.

“Cerebral profusion management has been widely adopted,” Dr. Trimarchi said. “Also there is an important trend showing an increasing utilization of antegrade cerebral profusion while we see a negative trend of the utilization of retrograde brain protection.”

Dr. Trimarchi attributed the detail the study generated to the survey form sent to the 26 IRAD-IVC sites around the world. The form measures 131 different variables, he said.

“Using this new specific surgical data form, we think we can address some surgical issues and report better data from the IRAD registry results on acute dissection,” he said. “These analyses have shown there have been significant changes in operative strategy over time in terms of managing such patients, and more importantly, a significant decrease in in-hospital mortality was observed in a 20-year time period.”

Dr. Trimarchi disclosed that he has received speaking and consulting fees and research support from W.L. Gore & Associates and Medtronic. IRAD is supported by W.L. Gore, Active Sites, Medtronic, Varbedian Aortic Research Fund, the Hewlett Foundation, the Mardigian Foundation, UM Faculty Group Practice, Terumo, and Ann and Bob Aikens.

NEW YORK – A study of an international database of individuals who have had open repair for acute type A aortic dissection (ATAAD) has revealed that in the past 20 years, cardiovascular surgeons have widely embraced valve-sparing procedures, bioprosthetic valves, and cerebral profusion strategies, according to a report here on the latest analysis of the database.

The most telling result is the decline in overall mortality, Santi Trimarchi, MD, PhD, of the University of Milan IRCCS Policlinico San Donato in Italy reported on behalf of the International Registry of Acute Aortic Dissection (IRAD) Interventional Cohort (IVC). The cohort analyzed surgery techniques and outcomes of 1,732 patients who had open repair from 1996 to 2016, clustering results in three time intervals: 1996-2003; 2004-2009; and 2010-2015.

“We noted in the registry that the overall in-hospital mortality rate was 14.3%, and this mortality decreased over time from 17.5% in the first six-year time span to 12.2% in the last six years,” Dr. Trimarchi said.

Among other trends the study identified are greater reliance on biological vs. mechanical valves, an increase in valve-sparing procedures, and steady use of Bentall procedures throughout the study period. “Operative techniques for redo aortic valve repair have been improving over the time, and that’s why we see more frequent use of biologic valves,” he said at the meeting, sponsored by the American Association for Thoracic Surgery.

“Cerebral profusion management has been widely adopted,” Dr. Trimarchi said. “Also there is an important trend showing an increasing utilization of antegrade cerebral profusion while we see a negative trend of the utilization of retrograde brain protection.”

Dr. Trimarchi attributed the detail the study generated to the survey form sent to the 26 IRAD-IVC sites around the world. The form measures 131 different variables, he said.

“Using this new specific surgical data form, we think we can address some surgical issues and report better data from the IRAD registry results on acute dissection,” he said. “These analyses have shown there have been significant changes in operative strategy over time in terms of managing such patients, and more importantly, a significant decrease in in-hospital mortality was observed in a 20-year time period.”

Dr. Trimarchi disclosed that he has received speaking and consulting fees and research support from W.L. Gore & Associates and Medtronic. IRAD is supported by W.L. Gore, Active Sites, Medtronic, Varbedian Aortic Research Fund, the Hewlett Foundation, the Mardigian Foundation, UM Faculty Group Practice, Terumo, and Ann and Bob Aikens.

Emergency physicians (EPs) have traditionally used the landmark technique to block the radial, ulnar, and median nerves at the wrist (Figure 1). Many times, however, there is a need to perform the block more proximally. Performing these blocks with real-time ultrasound guidance allows the clinician to visually target the nerve, requires less anesthetic agent, and helps to avoid vascular structures. As with any procedure, employing the appropriate technique, along with practice, increases the success of the block.

Patient Selection

Before performing a nerve block, the EP must first determine if the patient is an appropriate candidate. The EP should be cautious in performing a nerve block on any patient who has paresthesias, tingling, or weakness, as the block will complicate further examinations. Likewise, a nerve block may be contraindicated in a patient in whom compartment syndrome is a concern, since the analgesic effect will inhibit the patient’s ability to sense increasing pain or worsening paresthesias.

Equipment and Preprocedure Care

An ultrasound-guided nerve block is performed using the linear high-frequency probe. Prior to the procedure, standard infection-control measures should be taken—ie, thoroughly cleaning the preinjection site and using a transducer-probe cover. Regarding the choice of anesthetic, either bupivacaine or lidocaine is appropriate; however, bupivacaine will provide a longer duration of analgesia. To administer the anesthetic, we typically use a regular cutting needle or a spinal needle. A review of the literature typically suggests either noncutting needle tips or tips with short bevels. There is a paucity of data on needle tip selection. The use of noncutting needle tips or tips with short bevels may be a better choice than a regular cutting needle or a spinal needle because they may decrease the chance of intraneural injection and consequent nerve injury.

Single- Versus Two-Person Technique

Peripheral nerve blocks can be performed using either a single- or two-person technique. In the one-person technique, the operator manipulates both the probe and the syringe. The two-person technique, however, requires the addition of tubing between the needle and the syringe. This can be done with the addition of a small section of intravenous (IV) tubing or by connecting two pieces of tubing together (the type traditionally placed on IV catheters). The operator holds the needle and the probe while the syringe and injection are controlled by the second person. Then, with the ultrasound machine set at the nerve or soft-tissue presetting, the scan begins by placing the probe in a transverse orientation.

Nerve Location and Identification

As previously noted, the ulnar, median, and radial nerves have traditionally been identified through use of the landmark technique just proximal to the wrist. The nerves can be located initially at these sites and then traced proximally.

Ulnar Nerve

The ulnar nerve is located on the ulnar side of the forearm, just proximal to the wrist. (Figure 2a and 2b). The clinician should begin by fanning the probe at the wrist to find the ulnar artery and locate the nerve bundle. The ulnar nerve is also located on the ulnar side of the ulnar artery. The nerve will diverge from the path of the artery as it is traced proximally. To decrease the chance of an arterial injection/injury, the clinician should administer a nerve block after separating these two structures.

Median Nerve

The clinician can employ the landmark approach to help find the nerve; then the scan should begin at the carpal tunnel. On ultrasound, the tendons in the carpal tunnel will appear similar to nerves (ie, round and hyperechoic) compared to surrounding muscle. As one continues to slide the probe up the forearm, the tendons will become muscles and a single hyperechoic structure will remain—the median nerve running in between the flexor digitorum superificialis and the flexor digitorum profundus (Figure 3a and 3b). Since there is no artery alongside the median nerve, it can be traced proximally; therefore, the procedure can be performed in any convenient location.

Radial Nerve

Of the three nerves, the radial nerve is the most challenging to visualize on ultrasound. There are two approaches to performing a radial nerve block. In the first approach, the radial nerve can be found just proximal to the wrist crease on the radial side of the radial artery (Figure 4a and 4b). This nerve is typically much smaller and harder to visualize at this level; it can be traced proximally and the block performed at this location. In the second approach, the radial nerve can be located 3 to 4 cm proximal to the elbow with the probe located anterolaterally (Figure 5a and 5b). In this location, the radial nerve lies between the brachialis and the brachioradialis muscles. In this approach, the nerve is much larger and easier to visualize.

Performing the Block

Prior to performing an anesthetic block at the ulnar, median, or radial nerve at the wrist, the clinician should first place the patient in a sitting or supine position with the appropriate elbow extended. When performing the block at the radial nerve above the elbow, the hand is typically placed in a resting position on the patient’s abdomen. When localizing the nerve, the angle of the transducer can vary the appearance of the nerve dramatically. To ensure the best possible view, the clinician should slowly “rock” the probe back and forth 10° to 20° in plane with the long axis of the arm, making sure the probe is placed as perpendicular as possible to the nerve. Once the nerve is identified, the clinician can follow it up and down the forearm with the probe to identify the best site to perform the block. In the optimal location, there should be a clear path that is as superficial as possible and avoids any vascular structures. We prefer using an in-plane technique to perform the nerve block to visualize the entire needle as it approaches the nerve. Once the site has been determined, the clinician should slowly inject 4 to 5 cc of anesthetic around the nerve, with the objective to partially surround the nerve. There is no need to completely surround the nerve, as doing so is not necessary to achieve a successful block. The clinician should stop immediately if the patient reports pain or if there is increased resistance, because this could indicate an intraneural injection.

Summary

Ultrasound-guided peripheral nerve blocks are an excellent option for providing regional anesthesia to lacerations and wounds that are too large for a local anesthetic. This technique can provide better analgesic relief, enhancing patient care.

Emergency physicians (EPs) have traditionally used the landmark technique to block the radial, ulnar, and median nerves at the wrist (Figure 1). Many times, however, there is a need to perform the block more proximally. Performing these blocks with real-time ultrasound guidance allows the clinician to visually target the nerve, requires less anesthetic agent, and helps to avoid vascular structures. As with any procedure, employing the appropriate technique, along with practice, increases the success of the block.

Patient Selection

Before performing a nerve block, the EP must first determine if the patient is an appropriate candidate. The EP should be cautious in performing a nerve block on any patient who has paresthesias, tingling, or weakness, as the block will complicate further examinations. Likewise, a nerve block may be contraindicated in a patient in whom compartment syndrome is a concern, since the analgesic effect will inhibit the patient’s ability to sense increasing pain or worsening paresthesias.

Equipment and Preprocedure Care

An ultrasound-guided nerve block is performed using the linear high-frequency probe. Prior to the procedure, standard infection-control measures should be taken—ie, thoroughly cleaning the preinjection site and using a transducer-probe cover. Regarding the choice of anesthetic, either bupivacaine or lidocaine is appropriate; however, bupivacaine will provide a longer duration of analgesia. To administer the anesthetic, we typically use a regular cutting needle or a spinal needle. A review of the literature typically suggests either noncutting needle tips or tips with short bevels. There is a paucity of data on needle tip selection. The use of noncutting needle tips or tips with short bevels may be a better choice than a regular cutting needle or a spinal needle because they may decrease the chance of intraneural injection and consequent nerve injury.

Single- Versus Two-Person Technique

Peripheral nerve blocks can be performed using either a single- or two-person technique. In the one-person technique, the operator manipulates both the probe and the syringe. The two-person technique, however, requires the addition of tubing between the needle and the syringe. This can be done with the addition of a small section of intravenous (IV) tubing or by connecting two pieces of tubing together (the type traditionally placed on IV catheters). The operator holds the needle and the probe while the syringe and injection are controlled by the second person. Then, with the ultrasound machine set at the nerve or soft-tissue presetting, the scan begins by placing the probe in a transverse orientation.

Nerve Location and Identification

As previously noted, the ulnar, median, and radial nerves have traditionally been identified through use of the landmark technique just proximal to the wrist. The nerves can be located initially at these sites and then traced proximally.

Ulnar Nerve

The ulnar nerve is located on the ulnar side of the forearm, just proximal to the wrist. (Figure 2a and 2b). The clinician should begin by fanning the probe at the wrist to find the ulnar artery and locate the nerve bundle. The ulnar nerve is also located on the ulnar side of the ulnar artery. The nerve will diverge from the path of the artery as it is traced proximally. To decrease the chance of an arterial injection/injury, the clinician should administer a nerve block after separating these two structures.

Median Nerve

The clinician can employ the landmark approach to help find the nerve; then the scan should begin at the carpal tunnel. On ultrasound, the tendons in the carpal tunnel will appear similar to nerves (ie, round and hyperechoic) compared to surrounding muscle. As one continues to slide the probe up the forearm, the tendons will become muscles and a single hyperechoic structure will remain—the median nerve running in between the flexor digitorum superificialis and the flexor digitorum profundus (Figure 3a and 3b). Since there is no artery alongside the median nerve, it can be traced proximally; therefore, the procedure can be performed in any convenient location.

Radial Nerve

Of the three nerves, the radial nerve is the most challenging to visualize on ultrasound. There are two approaches to performing a radial nerve block. In the first approach, the radial nerve can be found just proximal to the wrist crease on the radial side of the radial artery (Figure 4a and 4b). This nerve is typically much smaller and harder to visualize at this level; it can be traced proximally and the block performed at this location. In the second approach, the radial nerve can be located 3 to 4 cm proximal to the elbow with the probe located anterolaterally (Figure 5a and 5b). In this location, the radial nerve lies between the brachialis and the brachioradialis muscles. In this approach, the nerve is much larger and easier to visualize.

Performing the Block

Prior to performing an anesthetic block at the ulnar, median, or radial nerve at the wrist, the clinician should first place the patient in a sitting or supine position with the appropriate elbow extended. When performing the block at the radial nerve above the elbow, the hand is typically placed in a resting position on the patient’s abdomen. When localizing the nerve, the angle of the transducer can vary the appearance of the nerve dramatically. To ensure the best possible view, the clinician should slowly “rock” the probe back and forth 10° to 20° in plane with the long axis of the arm, making sure the probe is placed as perpendicular as possible to the nerve. Once the nerve is identified, the clinician can follow it up and down the forearm with the probe to identify the best site to perform the block. In the optimal location, there should be a clear path that is as superficial as possible and avoids any vascular structures. We prefer using an in-plane technique to perform the nerve block to visualize the entire needle as it approaches the nerve. Once the site has been determined, the clinician should slowly inject 4 to 5 cc of anesthetic around the nerve, with the objective to partially surround the nerve. There is no need to completely surround the nerve, as doing so is not necessary to achieve a successful block. The clinician should stop immediately if the patient reports pain or if there is increased resistance, because this could indicate an intraneural injection.

Summary

Ultrasound-guided peripheral nerve blocks are an excellent option for providing regional anesthesia to lacerations and wounds that are too large for a local anesthetic. This technique can provide better analgesic relief, enhancing patient care.

Emergency physicians (EPs) have traditionally used the landmark technique to block the radial, ulnar, and median nerves at the wrist (Figure 1). Many times, however, there is a need to perform the block more proximally. Performing these blocks with real-time ultrasound guidance allows the clinician to visually target the nerve, requires less anesthetic agent, and helps to avoid vascular structures. As with any procedure, employing the appropriate technique, along with practice, increases the success of the block.

Patient Selection

Before performing a nerve block, the EP must first determine if the patient is an appropriate candidate. The EP should be cautious in performing a nerve block on any patient who has paresthesias, tingling, or weakness, as the block will complicate further examinations. Likewise, a nerve block may be contraindicated in a patient in whom compartment syndrome is a concern, since the analgesic effect will inhibit the patient’s ability to sense increasing pain or worsening paresthesias.

Equipment and Preprocedure Care

An ultrasound-guided nerve block is performed using the linear high-frequency probe. Prior to the procedure, standard infection-control measures should be taken—ie, thoroughly cleaning the preinjection site and using a transducer-probe cover. Regarding the choice of anesthetic, either bupivacaine or lidocaine is appropriate; however, bupivacaine will provide a longer duration of analgesia. To administer the anesthetic, we typically use a regular cutting needle or a spinal needle. A review of the literature typically suggests either noncutting needle tips or tips with short bevels. There is a paucity of data on needle tip selection. The use of noncutting needle tips or tips with short bevels may be a better choice than a regular cutting needle or a spinal needle because they may decrease the chance of intraneural injection and consequent nerve injury.

Single- Versus Two-Person Technique

Peripheral nerve blocks can be performed using either a single- or two-person technique. In the one-person technique, the operator manipulates both the probe and the syringe. The two-person technique, however, requires the addition of tubing between the needle and the syringe. This can be done with the addition of a small section of intravenous (IV) tubing or by connecting two pieces of tubing together (the type traditionally placed on IV catheters). The operator holds the needle and the probe while the syringe and injection are controlled by the second person. Then, with the ultrasound machine set at the nerve or soft-tissue presetting, the scan begins by placing the probe in a transverse orientation.

Nerve Location and Identification

As previously noted, the ulnar, median, and radial nerves have traditionally been identified through use of the landmark technique just proximal to the wrist. The nerves can be located initially at these sites and then traced proximally.

Ulnar Nerve

The ulnar nerve is located on the ulnar side of the forearm, just proximal to the wrist. (Figure 2a and 2b). The clinician should begin by fanning the probe at the wrist to find the ulnar artery and locate the nerve bundle. The ulnar nerve is also located on the ulnar side of the ulnar artery. The nerve will diverge from the path of the artery as it is traced proximally. To decrease the chance of an arterial injection/injury, the clinician should administer a nerve block after separating these two structures.

Median Nerve

The clinician can employ the landmark approach to help find the nerve; then the scan should begin at the carpal tunnel. On ultrasound, the tendons in the carpal tunnel will appear similar to nerves (ie, round and hyperechoic) compared to surrounding muscle. As one continues to slide the probe up the forearm, the tendons will become muscles and a single hyperechoic structure will remain—the median nerve running in between the flexor digitorum superificialis and the flexor digitorum profundus (Figure 3a and 3b). Since there is no artery alongside the median nerve, it can be traced proximally; therefore, the procedure can be performed in any convenient location.

Radial Nerve

Of the three nerves, the radial nerve is the most challenging to visualize on ultrasound. There are two approaches to performing a radial nerve block. In the first approach, the radial nerve can be found just proximal to the wrist crease on the radial side of the radial artery (Figure 4a and 4b). This nerve is typically much smaller and harder to visualize at this level; it can be traced proximally and the block performed at this location. In the second approach, the radial nerve can be located 3 to 4 cm proximal to the elbow with the probe located anterolaterally (Figure 5a and 5b). In this location, the radial nerve lies between the brachialis and the brachioradialis muscles. In this approach, the nerve is much larger and easier to visualize.

Performing the Block

Prior to performing an anesthetic block at the ulnar, median, or radial nerve at the wrist, the clinician should first place the patient in a sitting or supine position with the appropriate elbow extended. When performing the block at the radial nerve above the elbow, the hand is typically placed in a resting position on the patient’s abdomen. When localizing the nerve, the angle of the transducer can vary the appearance of the nerve dramatically. To ensure the best possible view, the clinician should slowly “rock” the probe back and forth 10° to 20° in plane with the long axis of the arm, making sure the probe is placed as perpendicular as possible to the nerve. Once the nerve is identified, the clinician can follow it up and down the forearm with the probe to identify the best site to perform the block. In the optimal location, there should be a clear path that is as superficial as possible and avoids any vascular structures. We prefer using an in-plane technique to perform the nerve block to visualize the entire needle as it approaches the nerve. Once the site has been determined, the clinician should slowly inject 4 to 5 cc of anesthetic around the nerve, with the objective to partially surround the nerve. There is no need to completely surround the nerve, as doing so is not necessary to achieve a successful block. The clinician should stop immediately if the patient reports pain or if there is increased resistance, because this could indicate an intraneural injection.

Summary

Ultrasound-guided peripheral nerve blocks are an excellent option for providing regional anesthesia to lacerations and wounds that are too large for a local anesthetic. This technique can provide better analgesic relief, enhancing patient care.

Case Scenarios

Case 1

While working abroad in a resource-limited environment, a patient was brought in after falling and hitting his head. Initially, the patient was awake and alert, but he gradually became minimally responsive, with a Glasgow Coma Scale score of 9. Your facility did not have computed tomography (CT) or magnetic resonance imaging (MRI), but did have a point-of-care ultrasound (US) machine. You measured the patient’s optic nerve sheath diameter (ONSD) with the US and found a diameter of 4.5 mm in each eye. With this clinical change, you wondered if repeat US scans to detect increasing intracranial pressure (ICP) would represent changes in the patient’s condition.

Case 2

A patient who presented with an intracranial hemorrhage was treated with hypertonic saline and was awaiting neurosurgical placement of an extraventicular drain. During this time, a resident who was on a US rotation asked you if she would be able to detect changes in the patient’s ICP using US rather than placing an invasive device. How do you respond?

In adults, ICP is normally 10 to 15 mm Hg. It may be pathologically increased in several life-threatening conditions, including traumatic brain injury (TBI), subarachnoid hemorrhage, central venous thrombosis, brain tumor, and abscess. It is also increased by nonacute pathology, such as idiopathic intracranial hypertension (IIH), which also is known as pseudotumor cerebri. In patients with acute pathology, ICP above 20 mm Hg is generally considered an indication for treatment.¹ Indications for ICP monitoring in TBI include positive CT findings, patient age greater than 40 years, systemic hypotension, or abnormal flexion/extension in response to pain.² Other reasons to monitor ICP include the management of pseudotumor cerebri or after ventriculoperitoneal shunt surgery.³

Unfortunately, current methods of ICP monitoring have significant drawbacks and limitations. The gold standard of ICP monitoring—measurement using an intraventricular catheter—increases the risks of infection and hemorrhage, requires the skill of a neurosurgeon, and may be contraindicated due to coagulopathy or thrombocytopenia. It also cannot be done in a prehospital setting and only to a limited extent in the ED.⁴

Computed tomography scans and MRI can assess elevated ICP, but these tests are expensive, may increase patient radiation exposure, require patient transport, and may not always detect raised ICP. In the appropriate clinical context, signs present on physical examination, such as decorticate/decerebrate posturing, papilledema, or fixed/dilated pupils, may be highly suggestive of an increased ICP, but sensitivity and specificity are inadequate. Delay in diagnosis is also a drawback of imaging and physical examination, as findings may not present until ICP has been persistently elevated.

Given the disadvantages of current means of assessing elevated ICP, several noninvasive methods of measuring ICP are being investigated. These include such techniques as transcranial Doppler, electroencephalogram, pupillometry, and ONSD measurements.⁵ This article reviews current applications of ultrasonography measurements of the ONSD in assessing elevations in ICP.

ONSD US

Assessment of ICP via measurement of the ONSD has attracted increasing attention, particularly in emergency medicine. Measurements of the ONSD are possible with CT, MRI, and US. Of these modalities, ONSD US has attracted the most interest, due to its low cost, wide availability, and rapidity. It does not require patient transport, and does not expose a patient to additional radiation. In addition, ONSD US has been utilized in low-resource settings, and may be particularly useful in prehospital and mass-casualty situations.⁶

The underlying relationship between ONSD and ICP is a result of the enclosure of the subarachnoid space by the ONS. Increased ICP leads to expansion of the ONS, particularly at 3 mm behind the globe, in the retrobulbar compartment (Figures 1 and 2).⁷

Unfortunately, it is not possible to precisely determine ICP from an ONSD measurement, because baseline ONSD values and elasticity vary significantly within the population.^4,8 As a result, ONSD US has been investigated mostly for its ability to detect qualitative changes—particularly as a screen for elevated ICP. Optic nerve sheath diameter has high discriminative value in its ability to distinguish normal from elevated ICP. In a meta-analysis, Dubourg et al⁹ showed that the technique had an area under the summary receiver-operating curve of 0.94, signifying excellent test accuracy to diagnose elevated ICPs.

Researchers have attempted to determine a threshold value of ONSD that would serve as a clinically useful predictor of elevated ICP. Currently, this value ranges from 4.8 to 5.9 mm, depending on the study⁹; 5 mm is commonly used clinically as a threshold.¹⁰

Using ONSD US to Monitor Rapid Changes in ICP

While the use of the ONSD technique to screen for elevated ICP is relatively well established, the use of ONSD US to track acute changes in ICP is not as well studied. Serial tracking of acute changes could be useful in a patient at risk for intracranial hypertension secondary to trauma, to monitor the results of treating a patient with IIH, or after ventriculoperitoneal shunt placement.³

In Vivo Data

In 1993, Tamburrelli et al¹¹ performed the first ONSD intrathecal infusion study, using A-scan sonography, and concluded that there was a “direct, biphasic, positive relation between diastolic intracranial pressure and optic nerve diameters” and that the data showed “rapid changes of optic nerve diameters in response to variation of intracranial pressure.”

In 1997, Hansen and Helmke¹² recorded ONSD versus ICP data in the first intrathecal infusion test to use B-scan mode sonography. Ultrasonography was performed at 2- to 4-minute intervals. Their data demonstrated a linear relationship between ICP and ONSD over a particular cerebrospinal fluid pressure interval. They noted that “this interval differed between patients: ONS dilation commenced at pressure thresholds between 15 mm Hg and 30 mm Hg and in some patients saturation of the response (constant ONSD) occurred between 30 mm Hg and 40 mm Hg.”

The slope of ONSD versus ICP curve varied considerably by patient, making it impossible to infer an absolute ICP value from an ONSD without prior knowledge of the patient’s ratio. Similar to the data from Tamburrelli et al,¹¹ Hansen and Helmke¹² also found that there was no lag in ONSD response to ICP: “Within this interval, no temporal delay of the ONS response was noted.”

The only study comparing real-time ONSD data to gold-standard measurements of rapidly changing ICP in humans was performed by Maissan et al¹³ in 2015. This study involved a cohort of 18 patients who had suffered TBI and had intraparenchymal probes inserted. Because ICP rises transiently during endotracheal tube suctioning due to irritation of the trachea, the increase and subsequent decrease after suctioning was an ideal time to perform ONSD measurements and compare them to simultaneous gold-standard ICP measurements. The ONSD US measurements were performed 30 to 60 seconds prior to suctioning, during suctioning, and 30 to 60 seconds after suctioning.

Even during this very rapid time course, a strong correlation between ICP and ONSD measurements was demonstrated. The R2 value was 0.80. There was no perceptible “lag” in ONSD change; changes in ICP were immediately reflected in ONSD. Notably, an absolute change of less than 8 to 10 mm Hg in ICP did not affect ONSD, which is consistent with data collected by Hansen and Helmke.¹²

Therapeutic Lumbar Puncture for IIH

There are two case reports of ONSD US measurements being taken pre- and postlumbar puncture (LP) in patients with IIH. In the first, in 1989 Galetta et al¹⁴ used A-scan US to measure pre- and post-LP ONSD in a woman with papilledema secondary to IIH. They found a significant reduction in ONSD bilaterally “within minutes” of performing the LP.¹⁴

The second case report was published in 2015 by Singleton et al.¹⁵ They recorded ONSD measurements 30 minutes pre- and post-LP in a woman who presented to the ED with symptoms from elevated ICP. After reduction of pressure via LP, they recorded a significant reduction in ONSD bilaterally.¹⁵

Cadaver Data

Hansen et al¹⁶ evaluated the distensibility and elasticity of the ONS using postmortem optic nerve preparations. The ONSD was recorded 200 seconds after each pressure increase, which was long enough to achieve stable diameters. They found a linear correlation between pressure increases of 5 to 45 mm Hg and ONSD. This would suggest a potential positively correlated change in ONSD with in vivo changes in ICP. However, this still needs further clinical study to better assess measurable changes in living patients.

Conclusion

Published data have consistently demonstrated that changes in ICP are rapidly transmitted to the optic nerve sheath and that there does not appear to be a temporal lag in the ONSD. Based on in vivo data, the relationship between ICP and ONSD appears to be linear only over a range of moderately elevated ICP. According to Hansen and Helmke,¹² this range starts at approximately 18 to 30 mm Hg, and ends at approximately 40 to 45 mm Hg. Maissan et al¹³ observed similar findings: “At low levels, ICP changes (8-10 mm Hg) do not affect the ONSD.”

There is still need for additional research to validate and refine these findings. Only one study has compared gold-standard ICP measurements with ONSD US measurements in real time,¹³ and the literature on ONSD US in tracking ICP after therapeutic LP in IIH consists of only two case reports.

Thus, with some caveats, ONSD US appears to permit qualitative tracking of ICP in real time. This supports its use in situations where a patient may have rapidly changing ICP, such as close monitoring of patients at risk for elevated ICP in a critical care setting, and response to treatment in patients with IIH.

Case Scenarios

Case 1

While working abroad in a resource-limited environment, a patient was brought in after falling and hitting his head. Initially, the patient was awake and alert, but he gradually became minimally responsive, with a Glasgow Coma Scale score of 9. Your facility did not have computed tomography (CT) or magnetic resonance imaging (MRI), but did have a point-of-care ultrasound (US) machine. You measured the patient’s optic nerve sheath diameter (ONSD) with the US and found a diameter of 4.5 mm in each eye. With this clinical change, you wondered if repeat US scans to detect increasing intracranial pressure (ICP) would represent changes in the patient’s condition.

Case 2

A patient who presented with an intracranial hemorrhage was treated with hypertonic saline and was awaiting neurosurgical placement of an extraventicular drain. During this time, a resident who was on a US rotation asked you if she would be able to detect changes in the patient’s ICP using US rather than placing an invasive device. How do you respond?

In adults, ICP is normally 10 to 15 mm Hg. It may be pathologically increased in several life-threatening conditions, including traumatic brain injury (TBI), subarachnoid hemorrhage, central venous thrombosis, brain tumor, and abscess. It is also increased by nonacute pathology, such as idiopathic intracranial hypertension (IIH), which also is known as pseudotumor cerebri. In patients with acute pathology, ICP above 20 mm Hg is generally considered an indication for treatment.¹ Indications for ICP monitoring in TBI include positive CT findings, patient age greater than 40 years, systemic hypotension, or abnormal flexion/extension in response to pain.² Other reasons to monitor ICP include the management of pseudotumor cerebri or after ventriculoperitoneal shunt surgery.³

Unfortunately, current methods of ICP monitoring have significant drawbacks and limitations. The gold standard of ICP monitoring—measurement using an intraventricular catheter—increases the risks of infection and hemorrhage, requires the skill of a neurosurgeon, and may be contraindicated due to coagulopathy or thrombocytopenia. It also cannot be done in a prehospital setting and only to a limited extent in the ED.⁴

Computed tomography scans and MRI can assess elevated ICP, but these tests are expensive, may increase patient radiation exposure, require patient transport, and may not always detect raised ICP. In the appropriate clinical context, signs present on physical examination, such as decorticate/decerebrate posturing, papilledema, or fixed/dilated pupils, may be highly suggestive of an increased ICP, but sensitivity and specificity are inadequate. Delay in diagnosis is also a drawback of imaging and physical examination, as findings may not present until ICP has been persistently elevated.

Given the disadvantages of current means of assessing elevated ICP, several noninvasive methods of measuring ICP are being investigated. These include such techniques as transcranial Doppler, electroencephalogram, pupillometry, and ONSD measurements.⁵ This article reviews current applications of ultrasonography measurements of the ONSD in assessing elevations in ICP.

ONSD US

Assessment of ICP via measurement of the ONSD has attracted increasing attention, particularly in emergency medicine. Measurements of the ONSD are possible with CT, MRI, and US. Of these modalities, ONSD US has attracted the most interest, due to its low cost, wide availability, and rapidity. It does not require patient transport, and does not expose a patient to additional radiation. In addition, ONSD US has been utilized in low-resource settings, and may be particularly useful in prehospital and mass-casualty situations.⁶

The underlying relationship between ONSD and ICP is a result of the enclosure of the subarachnoid space by the ONS. Increased ICP leads to expansion of the ONS, particularly at 3 mm behind the globe, in the retrobulbar compartment (Figures 1 and 2).⁷

Unfortunately, it is not possible to precisely determine ICP from an ONSD measurement, because baseline ONSD values and elasticity vary significantly within the population.^4,8 As a result, ONSD US has been investigated mostly for its ability to detect qualitative changes—particularly as a screen for elevated ICP. Optic nerve sheath diameter has high discriminative value in its ability to distinguish normal from elevated ICP. In a meta-analysis, Dubourg et al⁹ showed that the technique had an area under the summary receiver-operating curve of 0.94, signifying excellent test accuracy to diagnose elevated ICPs.

Researchers have attempted to determine a threshold value of ONSD that would serve as a clinically useful predictor of elevated ICP. Currently, this value ranges from 4.8 to 5.9 mm, depending on the study⁹; 5 mm is commonly used clinically as a threshold.¹⁰

Using ONSD US to Monitor Rapid Changes in ICP

While the use of the ONSD technique to screen for elevated ICP is relatively well established, the use of ONSD US to track acute changes in ICP is not as well studied. Serial tracking of acute changes could be useful in a patient at risk for intracranial hypertension secondary to trauma, to monitor the results of treating a patient with IIH, or after ventriculoperitoneal shunt placement.³

In Vivo Data

In 1993, Tamburrelli et al¹¹ performed the first ONSD intrathecal infusion study, using A-scan sonography, and concluded that there was a “direct, biphasic, positive relation between diastolic intracranial pressure and optic nerve diameters” and that the data showed “rapid changes of optic nerve diameters in response to variation of intracranial pressure.”

In 1997, Hansen and Helmke¹² recorded ONSD versus ICP data in the first intrathecal infusion test to use B-scan mode sonography. Ultrasonography was performed at 2- to 4-minute intervals. Their data demonstrated a linear relationship between ICP and ONSD over a particular cerebrospinal fluid pressure interval. They noted that “this interval differed between patients: ONS dilation commenced at pressure thresholds between 15 mm Hg and 30 mm Hg and in some patients saturation of the response (constant ONSD) occurred between 30 mm Hg and 40 mm Hg.”

The slope of ONSD versus ICP curve varied considerably by patient, making it impossible to infer an absolute ICP value from an ONSD without prior knowledge of the patient’s ratio. Similar to the data from Tamburrelli et al,¹¹ Hansen and Helmke¹² also found that there was no lag in ONSD response to ICP: “Within this interval, no temporal delay of the ONS response was noted.”

The only study comparing real-time ONSD data to gold-standard measurements of rapidly changing ICP in humans was performed by Maissan et al¹³ in 2015. This study involved a cohort of 18 patients who had suffered TBI and had intraparenchymal probes inserted. Because ICP rises transiently during endotracheal tube suctioning due to irritation of the trachea, the increase and subsequent decrease after suctioning was an ideal time to perform ONSD measurements and compare them to simultaneous gold-standard ICP measurements. The ONSD US measurements were performed 30 to 60 seconds prior to suctioning, during suctioning, and 30 to 60 seconds after suctioning.

Even during this very rapid time course, a strong correlation between ICP and ONSD measurements was demonstrated. The R2 value was 0.80. There was no perceptible “lag” in ONSD change; changes in ICP were immediately reflected in ONSD. Notably, an absolute change of less than 8 to 10 mm Hg in ICP did not affect ONSD, which is consistent with data collected by Hansen and Helmke.¹²

Therapeutic Lumbar Puncture for IIH

There are two case reports of ONSD US measurements being taken pre- and postlumbar puncture (LP) in patients with IIH. In the first, in 1989 Galetta et al¹⁴ used A-scan US to measure pre- and post-LP ONSD in a woman with papilledema secondary to IIH. They found a significant reduction in ONSD bilaterally “within minutes” of performing the LP.¹⁴

The second case report was published in 2015 by Singleton et al.¹⁵ They recorded ONSD measurements 30 minutes pre- and post-LP in a woman who presented to the ED with symptoms from elevated ICP. After reduction of pressure via LP, they recorded a significant reduction in ONSD bilaterally.¹⁵

Cadaver Data

Hansen et al¹⁶ evaluated the distensibility and elasticity of the ONS using postmortem optic nerve preparations. The ONSD was recorded 200 seconds after each pressure increase, which was long enough to achieve stable diameters. They found a linear correlation between pressure increases of 5 to 45 mm Hg and ONSD. This would suggest a potential positively correlated change in ONSD with in vivo changes in ICP. However, this still needs further clinical study to better assess measurable changes in living patients.

Conclusion

Published data have consistently demonstrated that changes in ICP are rapidly transmitted to the optic nerve sheath and that there does not appear to be a temporal lag in the ONSD. Based on in vivo data, the relationship between ICP and ONSD appears to be linear only over a range of moderately elevated ICP. According to Hansen and Helmke,¹² this range starts at approximately 18 to 30 mm Hg, and ends at approximately 40 to 45 mm Hg. Maissan et al¹³ observed similar findings: “At low levels, ICP changes (8-10 mm Hg) do not affect the ONSD.”

There is still need for additional research to validate and refine these findings. Only one study has compared gold-standard ICP measurements with ONSD US measurements in real time,¹³ and the literature on ONSD US in tracking ICP after therapeutic LP in IIH consists of only two case reports.

Thus, with some caveats, ONSD US appears to permit qualitative tracking of ICP in real time. This supports its use in situations where a patient may have rapidly changing ICP, such as close monitoring of patients at risk for elevated ICP in a critical care setting, and response to treatment in patients with IIH.

Case Scenarios

Case 1

While working abroad in a resource-limited environment, a patient was brought in after falling and hitting his head. Initially, the patient was awake and alert, but he gradually became minimally responsive, with a Glasgow Coma Scale score of 9. Your facility did not have computed tomography (CT) or magnetic resonance imaging (MRI), but did have a point-of-care ultrasound (US) machine. You measured the patient’s optic nerve sheath diameter (ONSD) with the US and found a diameter of 4.5 mm in each eye. With this clinical change, you wondered if repeat US scans to detect increasing intracranial pressure (ICP) would represent changes in the patient’s condition.

Case 2

A patient who presented with an intracranial hemorrhage was treated with hypertonic saline and was awaiting neurosurgical placement of an extraventicular drain. During this time, a resident who was on a US rotation asked you if she would be able to detect changes in the patient’s ICP using US rather than placing an invasive device. How do you respond?

In adults, ICP is normally 10 to 15 mm Hg. It may be pathologically increased in several life-threatening conditions, including traumatic brain injury (TBI), subarachnoid hemorrhage, central venous thrombosis, brain tumor, and abscess. It is also increased by nonacute pathology, such as idiopathic intracranial hypertension (IIH), which also is known as pseudotumor cerebri. In patients with acute pathology, ICP above 20 mm Hg is generally considered an indication for treatment.¹ Indications for ICP monitoring in TBI include positive CT findings, patient age greater than 40 years, systemic hypotension, or abnormal flexion/extension in response to pain.² Other reasons to monitor ICP include the management of pseudotumor cerebri or after ventriculoperitoneal shunt surgery.³

Unfortunately, current methods of ICP monitoring have significant drawbacks and limitations. The gold standard of ICP monitoring—measurement using an intraventricular catheter—increases the risks of infection and hemorrhage, requires the skill of a neurosurgeon, and may be contraindicated due to coagulopathy or thrombocytopenia. It also cannot be done in a prehospital setting and only to a limited extent in the ED.⁴

Computed tomography scans and MRI can assess elevated ICP, but these tests are expensive, may increase patient radiation exposure, require patient transport, and may not always detect raised ICP. In the appropriate clinical context, signs present on physical examination, such as decorticate/decerebrate posturing, papilledema, or fixed/dilated pupils, may be highly suggestive of an increased ICP, but sensitivity and specificity are inadequate. Delay in diagnosis is also a drawback of imaging and physical examination, as findings may not present until ICP has been persistently elevated.

Given the disadvantages of current means of assessing elevated ICP, several noninvasive methods of measuring ICP are being investigated. These include such techniques as transcranial Doppler, electroencephalogram, pupillometry, and ONSD measurements.⁵ This article reviews current applications of ultrasonography measurements of the ONSD in assessing elevations in ICP.

ONSD US

Assessment of ICP via measurement of the ONSD has attracted increasing attention, particularly in emergency medicine. Measurements of the ONSD are possible with CT, MRI, and US. Of these modalities, ONSD US has attracted the most interest, due to its low cost, wide availability, and rapidity. It does not require patient transport, and does not expose a patient to additional radiation. In addition, ONSD US has been utilized in low-resource settings, and may be particularly useful in prehospital and mass-casualty situations.⁶

The underlying relationship between ONSD and ICP is a result of the enclosure of the subarachnoid space by the ONS. Increased ICP leads to expansion of the ONS, particularly at 3 mm behind the globe, in the retrobulbar compartment (Figures 1 and 2).⁷

Unfortunately, it is not possible to precisely determine ICP from an ONSD measurement, because baseline ONSD values and elasticity vary significantly within the population.^4,8 As a result, ONSD US has been investigated mostly for its ability to detect qualitative changes—particularly as a screen for elevated ICP. Optic nerve sheath diameter has high discriminative value in its ability to distinguish normal from elevated ICP. In a meta-analysis, Dubourg et al⁹ showed that the technique had an area under the summary receiver-operating curve of 0.94, signifying excellent test accuracy to diagnose elevated ICPs.

Researchers have attempted to determine a threshold value of ONSD that would serve as a clinically useful predictor of elevated ICP. Currently, this value ranges from 4.8 to 5.9 mm, depending on the study⁹; 5 mm is commonly used clinically as a threshold.¹⁰

Using ONSD US to Monitor Rapid Changes in ICP

While the use of the ONSD technique to screen for elevated ICP is relatively well established, the use of ONSD US to track acute changes in ICP is not as well studied. Serial tracking of acute changes could be useful in a patient at risk for intracranial hypertension secondary to trauma, to monitor the results of treating a patient with IIH, or after ventriculoperitoneal shunt placement.³

In Vivo Data

In 1993, Tamburrelli et al¹¹ performed the first ONSD intrathecal infusion study, using A-scan sonography, and concluded that there was a “direct, biphasic, positive relation between diastolic intracranial pressure and optic nerve diameters” and that the data showed “rapid changes of optic nerve diameters in response to variation of intracranial pressure.”

In 1997, Hansen and Helmke¹² recorded ONSD versus ICP data in the first intrathecal infusion test to use B-scan mode sonography. Ultrasonography was performed at 2- to 4-minute intervals. Their data demonstrated a linear relationship between ICP and ONSD over a particular cerebrospinal fluid pressure interval. They noted that “this interval differed between patients: ONS dilation commenced at pressure thresholds between 15 mm Hg and 30 mm Hg and in some patients saturation of the response (constant ONSD) occurred between 30 mm Hg and 40 mm Hg.”

The slope of ONSD versus ICP curve varied considerably by patient, making it impossible to infer an absolute ICP value from an ONSD without prior knowledge of the patient’s ratio. Similar to the data from Tamburrelli et al,¹¹ Hansen and Helmke¹² also found that there was no lag in ONSD response to ICP: “Within this interval, no temporal delay of the ONS response was noted.”

The only study comparing real-time ONSD data to gold-standard measurements of rapidly changing ICP in humans was performed by Maissan et al¹³ in 2015. This study involved a cohort of 18 patients who had suffered TBI and had intraparenchymal probes inserted. Because ICP rises transiently during endotracheal tube suctioning due to irritation of the trachea, the increase and subsequent decrease after suctioning was an ideal time to perform ONSD measurements and compare them to simultaneous gold-standard ICP measurements. The ONSD US measurements were performed 30 to 60 seconds prior to suctioning, during suctioning, and 30 to 60 seconds after suctioning.

Even during this very rapid time course, a strong correlation between ICP and ONSD measurements was demonstrated. The R2 value was 0.80. There was no perceptible “lag” in ONSD change; changes in ICP were immediately reflected in ONSD. Notably, an absolute change of less than 8 to 10 mm Hg in ICP did not affect ONSD, which is consistent with data collected by Hansen and Helmke.¹²

Therapeutic Lumbar Puncture for IIH

There are two case reports of ONSD US measurements being taken pre- and postlumbar puncture (LP) in patients with IIH. In the first, in 1989 Galetta et al¹⁴ used A-scan US to measure pre- and post-LP ONSD in a woman with papilledema secondary to IIH. They found a significant reduction in ONSD bilaterally “within minutes” of performing the LP.¹⁴

The second case report was published in 2015 by Singleton et al.¹⁵ They recorded ONSD measurements 30 minutes pre- and post-LP in a woman who presented to the ED with symptoms from elevated ICP. After reduction of pressure via LP, they recorded a significant reduction in ONSD bilaterally.¹⁵

Cadaver Data

Hansen et al¹⁶ evaluated the distensibility and elasticity of the ONS using postmortem optic nerve preparations. The ONSD was recorded 200 seconds after each pressure increase, which was long enough to achieve stable diameters. They found a linear correlation between pressure increases of 5 to 45 mm Hg and ONSD. This would suggest a potential positively correlated change in ONSD with in vivo changes in ICP. However, this still needs further clinical study to better assess measurable changes in living patients.

Conclusion

Published data have consistently demonstrated that changes in ICP are rapidly transmitted to the optic nerve sheath and that there does not appear to be a temporal lag in the ONSD. Based on in vivo data, the relationship between ICP and ONSD appears to be linear only over a range of moderately elevated ICP. According to Hansen and Helmke,¹² this range starts at approximately 18 to 30 mm Hg, and ends at approximately 40 to 45 mm Hg. Maissan et al¹³ observed similar findings: “At low levels, ICP changes (8-10 mm Hg) do not affect the ONSD.”

There is still need for additional research to validate and refine these findings. Only one study has compared gold-standard ICP measurements with ONSD US measurements in real time,¹³ and the literature on ONSD US in tracking ICP after therapeutic LP in IIH consists of only two case reports.

Thus, with some caveats, ONSD US appears to permit qualitative tracking of ICP in real time. This supports its use in situations where a patient may have rapidly changing ICP, such as close monitoring of patients at risk for elevated ICP in a critical care setting, and response to treatment in patients with IIH.

An 18-year-old woman, pregnant for the third time, presented to the emergency department with constant vaginal bleeding and intermittent cramping for the past 3 weeks. Her last menstrual period was 14 weeks and 2 days ago. In her previous two pregnancies, she had given birth to one living child and had had one miscarriage.

Physical examination suggested that her uterus was bigger than expected for the gestational age, measuring 23 cm from the symphysis pubis to the uterine fundus. Ultrasonography in the obstetrics service revealed a “snowstorm” appearance strongly suggestive of molar pregnancy. Her level of beta human chorionic gonadotropin (beta-hCG) was greater than 1,125,000 mIU/mL (reference range for 14 weeks of pregnancy 18,300–137,000). Dilation and curettage was performed, and pathologic study confirmed molar pregnancy.

On the 6th day after the procedure, she returned to the emergency department with progressive abdominal pain, distention, and nausea. Her blood urea nitrogen level was 8 mg/dL (reference range 5–20 mg/dL) and her serum creatinine level was 0.5 mg/dL (0.5–0.9). Computed tomography of the abdomen and pelvis demonstrated an enlarged and bulky uterus with heterogeneous enhancement. The ovaries were greatly enlarged with multiple cysts, and massive ascites was noted in the abdomen (Figures 1 and 2). These findings confirmed the diagnosis of ovarian hyperstimulation syndrome (OHSS).

OVARIAN HYPERSTIMULATION SYNDROME

OHSS is enlargement of the ovaries associated with fluid shifts secondary to ovulation induction therapy with clomiphene citrate or hCG.¹ In its mild form, it is a common complication, seen in 5% to 10% of patients undergoing ovulation induction; the moderate form is reported in 2% to 4% of patients undergoing ovulation induction, and the severe form in 0.1% to 0.5%.² It may also occur spontaneously after pregnancy or with any condition that leads to a rise in hCG levels.

Factors associated with a high risk of developing OHSS include young age, low body weight, polycystic ovary syndrome, a high serum estradiol level, and a history of OHSS.^3,4

In our patient, OHSS was secondary to molar pregnancy and markedly elevated hCG levels. Hydatidiform mole or molar pregnancy is a cystic swelling of the chorionic villi and proliferation of the trophoblastic epithelium. Elevated circulating hCG is thought to lead to ovarian enlargement and multiple cysts; this stimulates the ovaries to secrete vasoactive substances, increasing vascular permeability, leading to fluid shifts and the accumulation of extravascular fluid, resulting in renal failure, hypovolemic shock, ascites, and pleural and pericardial effusions.⁵ This acute shift produces hypovolemia, which may result in multiple organ failure, hemoconcentration (hematocrit > 45%), thrombosis, and disseminated intravascular coagulation from the increased viscosity of the blood.

GRADING OF OHSS IS BASED ON SYMPTOMS, TEST RESULTS, IMAGING

The severity of OHSS is classified as mild, moderate, or severe, with further grading as follows^5,6:

Mild OHSS

• Grade 1: abdominal distention and discomfort.
• Grade 2: features of grade 1, plus nausea and vomiting, with or without diarrhea, and ovarian size of 5 to 12 cm.

Moderate OHSS

• Grade 3: mild OHSS with imaging evidence of ascites.

Severe OHSS

• Grade 4: moderate OHSS plus clinical evidence of ascites, with or without hydrothorax.
• Grade 5: all of the above plus hypovolemia, hemoconcentration (hematocrit > 45%), coagulation abnormalities, and oliguria.
• Grade 6: all the features of grades 1 to 4 plus hypovolemia, hemoconcentration (hematocrit > 55%), anuria, renal failure, venous thrombosis, and adult respiratory distress syndrome. This can be life-threatening and may require hospitalization.

TREATMENT

Treatment is generally conservative and includes management of ascites and pleural effusion and supportive care.

Mild OHSS can be treated on an outpatient basis with bed rest, oral analgesics, limited oral intake, and avoidance of vaginal intercourse, and usually resolves in 10 to 14 days. Moderate and severe OHSS require bed rest and aggressive fluid resuscitation. OHSS in patients with renal failure, relentless hemoconcentration, or thrombovascular accident can be life-threatening and may require intensive-care monitoring.

Paracentesis may be performed if tension ascites and oliguria or anuria develop.² Prophylactic anticoagulation with warfarin, heparin, or low-molecular-weight heparin is indicated in women with a high tendency for thrombotic events who develop moderate to severe OHSS.^3,4

Surgical intervention may be necessary in patients with ectopic pregnancy, ovarian torsion, or ruptured ovarian cyst.

Our patient was treated conservatively with supportive care and experienced a full recovery.

An 18-year-old woman, pregnant for the third time, presented to the emergency department with constant vaginal bleeding and intermittent cramping for the past 3 weeks. Her last menstrual period was 14 weeks and 2 days ago. In her previous two pregnancies, she had given birth to one living child and had had one miscarriage.

Physical examination suggested that her uterus was bigger than expected for the gestational age, measuring 23 cm from the symphysis pubis to the uterine fundus. Ultrasonography in the obstetrics service revealed a “snowstorm” appearance strongly suggestive of molar pregnancy. Her level of beta human chorionic gonadotropin (beta-hCG) was greater than 1,125,000 mIU/mL (reference range for 14 weeks of pregnancy 18,300–137,000). Dilation and curettage was performed, and pathologic study confirmed molar pregnancy.

On the 6th day after the procedure, she returned to the emergency department with progressive abdominal pain, distention, and nausea. Her blood urea nitrogen level was 8 mg/dL (reference range 5–20 mg/dL) and her serum creatinine level was 0.5 mg/dL (0.5–0.9). Computed tomography of the abdomen and pelvis demonstrated an enlarged and bulky uterus with heterogeneous enhancement. The ovaries were greatly enlarged with multiple cysts, and massive ascites was noted in the abdomen (Figures 1 and 2). These findings confirmed the diagnosis of ovarian hyperstimulation syndrome (OHSS).

OVARIAN HYPERSTIMULATION SYNDROME

OHSS is enlargement of the ovaries associated with fluid shifts secondary to ovulation induction therapy with clomiphene citrate or hCG.¹ In its mild form, it is a common complication, seen in 5% to 10% of patients undergoing ovulation induction; the moderate form is reported in 2% to 4% of patients undergoing ovulation induction, and the severe form in 0.1% to 0.5%.² It may also occur spontaneously after pregnancy or with any condition that leads to a rise in hCG levels.

Factors associated with a high risk of developing OHSS include young age, low body weight, polycystic ovary syndrome, a high serum estradiol level, and a history of OHSS.^3,4

In our patient, OHSS was secondary to molar pregnancy and markedly elevated hCG levels. Hydatidiform mole or molar pregnancy is a cystic swelling of the chorionic villi and proliferation of the trophoblastic epithelium. Elevated circulating hCG is thought to lead to ovarian enlargement and multiple cysts; this stimulates the ovaries to secrete vasoactive substances, increasing vascular permeability, leading to fluid shifts and the accumulation of extravascular fluid, resulting in renal failure, hypovolemic shock, ascites, and pleural and pericardial effusions.⁵ This acute shift produces hypovolemia, which may result in multiple organ failure, hemoconcentration (hematocrit > 45%), thrombosis, and disseminated intravascular coagulation from the increased viscosity of the blood.

GRADING OF OHSS IS BASED ON SYMPTOMS, TEST RESULTS, IMAGING

The severity of OHSS is classified as mild, moderate, or severe, with further grading as follows^5,6:

Mild OHSS

• Grade 1: abdominal distention and discomfort.
• Grade 2: features of grade 1, plus nausea and vomiting, with or without diarrhea, and ovarian size of 5 to 12 cm.

Moderate OHSS

• Grade 3: mild OHSS with imaging evidence of ascites.

Severe OHSS

• Grade 4: moderate OHSS plus clinical evidence of ascites, with or without hydrothorax.
• Grade 5: all of the above plus hypovolemia, hemoconcentration (hematocrit > 45%), coagulation abnormalities, and oliguria.
• Grade 6: all the features of grades 1 to 4 plus hypovolemia, hemoconcentration (hematocrit > 55%), anuria, renal failure, venous thrombosis, and adult respiratory distress syndrome. This can be life-threatening and may require hospitalization.

TREATMENT

Treatment is generally conservative and includes management of ascites and pleural effusion and supportive care.

Mild OHSS can be treated on an outpatient basis with bed rest, oral analgesics, limited oral intake, and avoidance of vaginal intercourse, and usually resolves in 10 to 14 days. Moderate and severe OHSS require bed rest and aggressive fluid resuscitation. OHSS in patients with renal failure, relentless hemoconcentration, or thrombovascular accident can be life-threatening and may require intensive-care monitoring.

Paracentesis may be performed if tension ascites and oliguria or anuria develop.² Prophylactic anticoagulation with warfarin, heparin, or low-molecular-weight heparin is indicated in women with a high tendency for thrombotic events who develop moderate to severe OHSS.^3,4

Surgical intervention may be necessary in patients with ectopic pregnancy, ovarian torsion, or ruptured ovarian cyst.

Our patient was treated conservatively with supportive care and experienced a full recovery.

An 18-year-old woman, pregnant for the third time, presented to the emergency department with constant vaginal bleeding and intermittent cramping for the past 3 weeks. Her last menstrual period was 14 weeks and 2 days ago. In her previous two pregnancies, she had given birth to one living child and had had one miscarriage.

Physical examination suggested that her uterus was bigger than expected for the gestational age, measuring 23 cm from the symphysis pubis to the uterine fundus. Ultrasonography in the obstetrics service revealed a “snowstorm” appearance strongly suggestive of molar pregnancy. Her level of beta human chorionic gonadotropin (beta-hCG) was greater than 1,125,000 mIU/mL (reference range for 14 weeks of pregnancy 18,300–137,000). Dilation and curettage was performed, and pathologic study confirmed molar pregnancy.

On the 6th day after the procedure, she returned to the emergency department with progressive abdominal pain, distention, and nausea. Her blood urea nitrogen level was 8 mg/dL (reference range 5–20 mg/dL) and her serum creatinine level was 0.5 mg/dL (0.5–0.9). Computed tomography of the abdomen and pelvis demonstrated an enlarged and bulky uterus with heterogeneous enhancement. The ovaries were greatly enlarged with multiple cysts, and massive ascites was noted in the abdomen (Figures 1 and 2). These findings confirmed the diagnosis of ovarian hyperstimulation syndrome (OHSS).

OVARIAN HYPERSTIMULATION SYNDROME

OHSS is enlargement of the ovaries associated with fluid shifts secondary to ovulation induction therapy with clomiphene citrate or hCG.¹ In its mild form, it is a common complication, seen in 5% to 10% of patients undergoing ovulation induction; the moderate form is reported in 2% to 4% of patients undergoing ovulation induction, and the severe form in 0.1% to 0.5%.² It may also occur spontaneously after pregnancy or with any condition that leads to a rise in hCG levels.

Factors associated with a high risk of developing OHSS include young age, low body weight, polycystic ovary syndrome, a high serum estradiol level, and a history of OHSS.^3,4

In our patient, OHSS was secondary to molar pregnancy and markedly elevated hCG levels. Hydatidiform mole or molar pregnancy is a cystic swelling of the chorionic villi and proliferation of the trophoblastic epithelium. Elevated circulating hCG is thought to lead to ovarian enlargement and multiple cysts; this stimulates the ovaries to secrete vasoactive substances, increasing vascular permeability, leading to fluid shifts and the accumulation of extravascular fluid, resulting in renal failure, hypovolemic shock, ascites, and pleural and pericardial effusions.⁵ This acute shift produces hypovolemia, which may result in multiple organ failure, hemoconcentration (hematocrit > 45%), thrombosis, and disseminated intravascular coagulation from the increased viscosity of the blood.

GRADING OF OHSS IS BASED ON SYMPTOMS, TEST RESULTS, IMAGING

The severity of OHSS is classified as mild, moderate, or severe, with further grading as follows^5,6:

Mild OHSS

• Grade 1: abdominal distention and discomfort.
• Grade 2: features of grade 1, plus nausea and vomiting, with or without diarrhea, and ovarian size of 5 to 12 cm.

Moderate OHSS

• Grade 3: mild OHSS with imaging evidence of ascites.

Severe OHSS

• Grade 4: moderate OHSS plus clinical evidence of ascites, with or without hydrothorax.
• Grade 5: all of the above plus hypovolemia, hemoconcentration (hematocrit > 45%), coagulation abnormalities, and oliguria.
• Grade 6: all the features of grades 1 to 4 plus hypovolemia, hemoconcentration (hematocrit > 55%), anuria, renal failure, venous thrombosis, and adult respiratory distress syndrome. This can be life-threatening and may require hospitalization.

TREATMENT

Treatment is generally conservative and includes management of ascites and pleural effusion and supportive care.

Mild OHSS can be treated on an outpatient basis with bed rest, oral analgesics, limited oral intake, and avoidance of vaginal intercourse, and usually resolves in 10 to 14 days. Moderate and severe OHSS require bed rest and aggressive fluid resuscitation. OHSS in patients with renal failure, relentless hemoconcentration, or thrombovascular accident can be life-threatening and may require intensive-care monitoring.

Paracentesis may be performed if tension ascites and oliguria or anuria develop.² Prophylactic anticoagulation with warfarin, heparin, or low-molecular-weight heparin is indicated in women with a high tendency for thrombotic events who develop moderate to severe OHSS.^3,4

Surgical intervention may be necessary in patients with ectopic pregnancy, ovarian torsion, or ruptured ovarian cyst.

Our patient was treated conservatively with supportive care and experienced a full recovery.

PARIS – Intravascular ultrasound can reliably be used in lieu of multidetector computerized tomography for the key task of annular sizing in patients undergoing transcatheter aortic valve replacement, Dr. Diaa Hakim declared at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

Multidetector CT (MDCT) is considered the standard imaging method for this purpose. But the requirement for contrast media makes MDCT problematic for patients with chronic kidney disease, who can easily be driven into acute kidney injury through exposure to this material.

Bruce Jancin/Frontline Medical News

Moreover, renal failure is common among patients with a failing native aortic valve. Interventionalists who perform transaortic valve replacement (TAVR) are encountering renal failure more and more frequently as the nonsurgical treatment takes off in popularity. An alternative imaging method is sorely needed, observed Dr. Hakim of the University of Alabama at Birmingham.

Unlike MDCT, intravascular ultrasound (IVUS) doesn’t require contrast. And in Dr. Hakim’s head-to-head comparative trial conducted in 50 consecutive TAVR patients who underwent annular sizing by both methods, there were no significant differences between the two in measurements of maximum and minimum annular diameter, mean annular diameter, or annular area.

The decision as to the size of the replacement aortic valve was based upon MDCT, which was performed first. Then came IVUS carried out with a Boston Science Atlantis PV Peripheral IVUS catheter at 8-French and 15 Hz. The catheter was advanced over the guidewire, then pullback imaging was obtained automatically from the left ventricular outflow tract to the aortic root. The IVUS measurements were made at the level of basal attachment of the aortic valve cusps, which was quite close to the same point as the MDCT measurements.

Post TAVR, 37 of the 50 patients had no or trivial paravalvular regurgitation. Six patients developed acute kidney injury.

Asked if he believes IVUS now enables operators to routinely skip MDCT for TAVR patients, Dr. Hakim replied, “Not for the moment.” In patients with chronic kidney disease, yes, but in order for IVUS for annular sizing to expand beyond that population it will be necessary for device makers to develop an IVUS catheter with better visualization, a device designed specifically to see all the details of the aortic valve and annulus. He noted that the Atlantis PV Peripheral IVUS catheter employed in his study was designed for the aorta, not the aortic valve. It doesn’t provide optimal imaging of the valve cusps, nor can it measure paravalvular regurgitation after valve implantation.

How much time does IVUS for annular sizing add to the TAVR procedure? “Five minutes, no more,” according to Dr. Hakim.

He reported having no financial conflicts regarding this study, conducted free of commercial support.

[email protected]

PARIS – Intravascular ultrasound can reliably be used in lieu of multidetector computerized tomography for the key task of annular sizing in patients undergoing transcatheter aortic valve replacement, Dr. Diaa Hakim declared at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

Multidetector CT (MDCT) is considered the standard imaging method for this purpose. But the requirement for contrast media makes MDCT problematic for patients with chronic kidney disease, who can easily be driven into acute kidney injury through exposure to this material.

Bruce Jancin/Frontline Medical News

Moreover, renal failure is common among patients with a failing native aortic valve. Interventionalists who perform transaortic valve replacement (TAVR) are encountering renal failure more and more frequently as the nonsurgical treatment takes off in popularity. An alternative imaging method is sorely needed, observed Dr. Hakim of the University of Alabama at Birmingham.

Unlike MDCT, intravascular ultrasound (IVUS) doesn’t require contrast. And in Dr. Hakim’s head-to-head comparative trial conducted in 50 consecutive TAVR patients who underwent annular sizing by both methods, there were no significant differences between the two in measurements of maximum and minimum annular diameter, mean annular diameter, or annular area.

The decision as to the size of the replacement aortic valve was based upon MDCT, which was performed first. Then came IVUS carried out with a Boston Science Atlantis PV Peripheral IVUS catheter at 8-French and 15 Hz. The catheter was advanced over the guidewire, then pullback imaging was obtained automatically from the left ventricular outflow tract to the aortic root. The IVUS measurements were made at the level of basal attachment of the aortic valve cusps, which was quite close to the same point as the MDCT measurements.

Post TAVR, 37 of the 50 patients had no or trivial paravalvular regurgitation. Six patients developed acute kidney injury.

Asked if he believes IVUS now enables operators to routinely skip MDCT for TAVR patients, Dr. Hakim replied, “Not for the moment.” In patients with chronic kidney disease, yes, but in order for IVUS for annular sizing to expand beyond that population it will be necessary for device makers to develop an IVUS catheter with better visualization, a device designed specifically to see all the details of the aortic valve and annulus. He noted that the Atlantis PV Peripheral IVUS catheter employed in his study was designed for the aorta, not the aortic valve. It doesn’t provide optimal imaging of the valve cusps, nor can it measure paravalvular regurgitation after valve implantation.

How much time does IVUS for annular sizing add to the TAVR procedure? “Five minutes, no more,” according to Dr. Hakim.

He reported having no financial conflicts regarding this study, conducted free of commercial support.

[email protected]

PARIS – Intravascular ultrasound can reliably be used in lieu of multidetector computerized tomography for the key task of annular sizing in patients undergoing transcatheter aortic valve replacement, Dr. Diaa Hakim declared at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

Multidetector CT (MDCT) is considered the standard imaging method for this purpose. But the requirement for contrast media makes MDCT problematic for patients with chronic kidney disease, who can easily be driven into acute kidney injury through exposure to this material.

Bruce Jancin/Frontline Medical News

Moreover, renal failure is common among patients with a failing native aortic valve. Interventionalists who perform transaortic valve replacement (TAVR) are encountering renal failure more and more frequently as the nonsurgical treatment takes off in popularity. An alternative imaging method is sorely needed, observed Dr. Hakim of the University of Alabama at Birmingham.

Unlike MDCT, intravascular ultrasound (IVUS) doesn’t require contrast. And in Dr. Hakim’s head-to-head comparative trial conducted in 50 consecutive TAVR patients who underwent annular sizing by both methods, there were no significant differences between the two in measurements of maximum and minimum annular diameter, mean annular diameter, or annular area.

The decision as to the size of the replacement aortic valve was based upon MDCT, which was performed first. Then came IVUS carried out with a Boston Science Atlantis PV Peripheral IVUS catheter at 8-French and 15 Hz. The catheter was advanced over the guidewire, then pullback imaging was obtained automatically from the left ventricular outflow tract to the aortic root. The IVUS measurements were made at the level of basal attachment of the aortic valve cusps, which was quite close to the same point as the MDCT measurements.

Post TAVR, 37 of the 50 patients had no or trivial paravalvular regurgitation. Six patients developed acute kidney injury.

Asked if he believes IVUS now enables operators to routinely skip MDCT for TAVR patients, Dr. Hakim replied, “Not for the moment.” In patients with chronic kidney disease, yes, but in order for IVUS for annular sizing to expand beyond that population it will be necessary for device makers to develop an IVUS catheter with better visualization, a device designed specifically to see all the details of the aortic valve and annulus. He noted that the Atlantis PV Peripheral IVUS catheter employed in his study was designed for the aorta, not the aortic valve. It doesn’t provide optimal imaging of the valve cusps, nor can it measure paravalvular regurgitation after valve implantation.

How much time does IVUS for annular sizing add to the TAVR procedure? “Five minutes, no more,” according to Dr. Hakim.

He reported having no financial conflicts regarding this study, conducted free of commercial support.

[email protected]

SAN DIEGO – Assessment of the trachea and pleura via point-of-care ultrasound is superior to auscultation in determining the exact location of the endotracheal tube, a randomized, single-center study found.

“It’s been reported that about 20% of the time the endotracheal tube is malpositioned,” study author Dr. Davinder S. Ramsingh said in an interview at the annual meeting of the American Society of Anesthesiologists. “Most of the time (the tube) is too deep, which can lead to severe complications.”

In a double-blinded, randomized study, Dr. Ramsingh and his associates assessed the accuracy of auscultation vs. point-of-care ultrasound in verifying the correct position of the endotracheal tube (ETT). They enrolled 42 adults who required general anesthesia with ETT and randomized them to right main bronchus, left main bronchus, or tracheal intubation, followed by fiber optically–guided visualization to place the ETT. Next, an anesthesiologist blinded to the ETT exact location used auscultation to assess the location of the ETT, while another anesthesiologist blinded to the ETT exact location used point-of-care ultrasound to assess the location of the ETT. The ultrasound exam consisted of assessing tracheal dilation via standard cuff inflation with air and evaluation of pleural lung sliding, explained Dr. Ramsingh of the department of anesthesiology and perioperative care at the University of California, Irvine.

Dr. Ramsingh reported that in differentiating tracheal versus bronchial intubations, auscultation demonstrated a sensitivity of 66% and a specificity of 59%, while ultrasound demonstrated a sensitivity of 93% and a specificity of 96%. Chi-square comparison showed a statistically significant improvement with ultrasound (P = .0005), while inter-observer agreement of the ultrasound findings was 100%.

Limitations of the study, he said, include the fact that “we don’t know the incidence of malpositioned endotracheal tubes in the operating room and that this study was evaluating patients undergoing elective surgical procedures.”

The researchers reported having no financial disclosures.

[email protected]

SAN DIEGO – Assessment of the trachea and pleura via point-of-care ultrasound is superior to auscultation in determining the exact location of the endotracheal tube, a randomized, single-center study found.

“It’s been reported that about 20% of the time the endotracheal tube is malpositioned,” study author Dr. Davinder S. Ramsingh said in an interview at the annual meeting of the American Society of Anesthesiologists. “Most of the time (the tube) is too deep, which can lead to severe complications.”

In a double-blinded, randomized study, Dr. Ramsingh and his associates assessed the accuracy of auscultation vs. point-of-care ultrasound in verifying the correct position of the endotracheal tube (ETT). They enrolled 42 adults who required general anesthesia with ETT and randomized them to right main bronchus, left main bronchus, or tracheal intubation, followed by fiber optically–guided visualization to place the ETT. Next, an anesthesiologist blinded to the ETT exact location used auscultation to assess the location of the ETT, while another anesthesiologist blinded to the ETT exact location used point-of-care ultrasound to assess the location of the ETT. The ultrasound exam consisted of assessing tracheal dilation via standard cuff inflation with air and evaluation of pleural lung sliding, explained Dr. Ramsingh of the department of anesthesiology and perioperative care at the University of California, Irvine.

Dr. Ramsingh reported that in differentiating tracheal versus bronchial intubations, auscultation demonstrated a sensitivity of 66% and a specificity of 59%, while ultrasound demonstrated a sensitivity of 93% and a specificity of 96%. Chi-square comparison showed a statistically significant improvement with ultrasound (P = .0005), while inter-observer agreement of the ultrasound findings was 100%.

Limitations of the study, he said, include the fact that “we don’t know the incidence of malpositioned endotracheal tubes in the operating room and that this study was evaluating patients undergoing elective surgical procedures.”

The researchers reported having no financial disclosures.

[email protected]

SAN DIEGO – Assessment of the trachea and pleura via point-of-care ultrasound is superior to auscultation in determining the exact location of the endotracheal tube, a randomized, single-center study found.

“It’s been reported that about 20% of the time the endotracheal tube is malpositioned,” study author Dr. Davinder S. Ramsingh said in an interview at the annual meeting of the American Society of Anesthesiologists. “Most of the time (the tube) is too deep, which can lead to severe complications.”

In a double-blinded, randomized study, Dr. Ramsingh and his associates assessed the accuracy of auscultation vs. point-of-care ultrasound in verifying the correct position of the endotracheal tube (ETT). They enrolled 42 adults who required general anesthesia with ETT and randomized them to right main bronchus, left main bronchus, or tracheal intubation, followed by fiber optically–guided visualization to place the ETT. Next, an anesthesiologist blinded to the ETT exact location used auscultation to assess the location of the ETT, while another anesthesiologist blinded to the ETT exact location used point-of-care ultrasound to assess the location of the ETT. The ultrasound exam consisted of assessing tracheal dilation via standard cuff inflation with air and evaluation of pleural lung sliding, explained Dr. Ramsingh of the department of anesthesiology and perioperative care at the University of California, Irvine.

Dr. Ramsingh reported that in differentiating tracheal versus bronchial intubations, auscultation demonstrated a sensitivity of 66% and a specificity of 59%, while ultrasound demonstrated a sensitivity of 93% and a specificity of 96%. Chi-square comparison showed a statistically significant improvement with ultrasound (P = .0005), while inter-observer agreement of the ultrasound findings was 100%.

Limitations of the study, he said, include the fact that “we don’t know the incidence of malpositioned endotracheal tubes in the operating room and that this study was evaluating patients undergoing elective surgical procedures.”

The researchers reported having no financial disclosures.

[email protected]

The distal or proximal femur with tumor endoprosthesis is commonly replaced after segmental resections for bone tumors, complex trauma, or revision arthroplasty. In conventional joint replacements, correct rotational alignment of the component is referenced off anatomical landmarks in the proximal or distal femur. After tumor resection, however, these landmarks are often not available for rotational orientation. There are no reports of studies validating a particular method of establishing rotation in these cases.

To establish a guide for rotational alignment of tumor endoprostheses, we set out to define the natural location of the linea aspera (LA) based on axial computed tomography (CT) scans. The LA is often the most outstanding visible bony landmark on a cross-section of the femur during surgery, and it would be helpful to know its normal orientation in relation to the true anteroposterior (AP) axis of the femur and to the femoral version. We wanted to answer these 5 questions:

1. Is the prominence of the LA easily identifiable on cross-section at different levels of the femoral shaft?

2. Does an axis passing through the LA correspond to the AP axis of the femur?

3. If not, is this axis offset internally or externally and by how much?

4. Is this offset constant at all levels of the femoral shaft?

5. How does the LA axis relate to the femoral neck axis at these levels?

The answers determine if the LA can be reliably used for rotational alignment of tumor endoprostheses.

Materials and Methods

After this study received Institutional Review Board approval, we retrospectively reviewed whole-body fluorine-18-deoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) studies performed in our hospital between 2003 and 2006 to identify those with full-length bilateral femur CT scans. These scans were available on the hospital’s computerized picture archiving system (General Electric). Patients could be included in the study as long as they were at least 18 years old at time of scan and did not have any pathology that deformed the femur, broke a cortex, or otherwise caused any gross asymmetry of the femur. Of the 72 patients with full-length femur CT scans, 3 were excluded: 1 with a congenital hip dysplasia, 1 with an old, malunited femoral fracture, and 1 who was 15 years old at time of scan.

Axial Slice Selection

For each patient, scout AP films were used to measure femoral shaft length from the top of the greater trochanter to the end of the lateral femoral condyle. The levels of the proximal third, midshaft, and distal third were then calculated based on this length. The LA was studied on the axial slices nearest these levels. Next, we scrolled through the scans to identify an axial slice that best showed the femoral neck axis. The literature on CT measurement of femoral anteversion is varied. Some articles describe a technique that uses 2 superimposed axial slices, and others describe a single axial slice.^1-3 We used 1 axial slice to draw the femoral neck axis because our computer software could not superimpose 2 images on 1 screen and because the CT scans were not made under specific protocols to measure anteversion but rather were part of a cancer staging work-up. Axial cuts were made at 5-mm intervals, and not all scans included a single slice capturing the head, neck, and greater trochanter. Therefore, we used a (previously described) method in which the femoral neck axis is drawn on a slice that most captured the femoral neck, usually toward its base.4 Last, in order to draw the posterior condyle (PC) axis, we selected an axial slice that showed the posterior-most aspects of the femoral condyles at the intercondylar notch.

Determining Anteroposterior and Posterior Condyle Axes of Femur

As we made all measurements for each femur off a single CT scan, we were able to use a straight horizontal line—drawn on-screen with a software tool—as a reference for measuring rotation. On a distal femur cut, the PC axis is drawn by connecting the posterior-most points of both condyles. The software calculates the angle formed—the PC angle (Figure 1). This angle, the degree to which the PC axis deviates from a straight horizontal line on-screen, can be used to account for gross rotation of the limb on comparison of images. The AP axis of the femur is the axis perpendicular to the PC axis. As such, the PC angle can also be used to determine degree of deviation of the AP axis from a straight vertical line on-screen. The AP axis was used when calculating the LA axis at the various levels of the femur (Figure 2).

Femoral Version

We used the software tool to draw the femoral neck axis. From the end of this line, a straight horizontal line is drawn on-screen (Figure 3). The software calculates the angle formed—the femoral neck axis angle. We assigned a positive value for a femoral head that pointed anteriorly on the image and a negative value for a head that pointed posteriorly. Adjusting for external rotation of the limb involved calculating the femoral version by subtracting the PC angle from the neck axis angle; adjusting for internal rotation involved adding these 2 angles.

Linea Aspera Morphology

After viewing the first 20 CT scans, we identified 3 types of LA morphology. Type I presents as a thickening on the posterior cortex with a sharp apex; type II presents as a flat-faced but distinct ridge of bone between the medial and lateral lips; and in type III there is no distinct cortical thickening with blunted medial and lateral lips; the latter is always more prominent.

Linea Aspera Axis Offset

From the most posterior point of the LA, a line drawn forward bisecting the femoral canal defined the LA axis. In type I morphology, the posterior-most point was the apex; in type II, the middle of flat posterior surface was used as the starting point; in type III, the lateral lip was used, as it was sharper than the medial lip. This line is again referenced with a straight horizontal line across the image. The PC angle is then added to account for limb rotation, and the result is the LA angle. As the AP axis is perpendicular to the PC axis, the LA angle is subtracted from 90°; the difference represents the amount of offset of the LA axis from the AP axis. By convention, we assigned this a positive value for an LA lateral to the midpoint of the femur and a negative value for an LA medial to the midpoint (Figure 4).

Linea Aspera Axis and Femoral Neck Axis

The angle between the LA axis and the PC axis was measured. The femoral version angle was subtracted from that angle to obtain the arc between the LA axis and the femoral neck axis.

Statistical Analyses

All analyses were performed with SAS 9.1 (SAS Institute). All tests were 2-sided and conducted at the .05 significance level. No adjustments were made for multiple testing. Statistical analysis was performed with nonparametric tests and without making assumptions about the distribution of the study population. Univariate analyses were performed to test for significant side-to-side differences in femoral length, femoral version angle, and LA torsion angles at each level. A multivariate analysis was performed to test for interactions between sex, side, and level. In all analyses, P < .05 was used as the cutoff value for statistical significance.

Results

Femoral lengths varied by side and sex. The left side was longer than the right by a mean of 1.3 mm (P = .008). With multivariate analysis taking into account sex and age (cumulated per decade), there was still a significant effect of side on femoral length. Sex also had a significant effect on femoral length, with females’ femurs shorter by 21.7 mm (standard error, 5.0 mm). Mean (SD) anteversion of the femoral neck was 7.9° (12.7°) on the left and 13.3° (13.0°) on the right; the difference between sides was significant (P < .001). In a multivariate analysis performed to identify potential predictors of femoral version, side still had a significant (P < .001) independent effect; sex and age did not have an effect.

LA morphology varied according to femoral shaft level (Table 1). The morphology was type I in 75% of patients at the distal femur and 74% of patients at the midshaft femur, while only 53% of patients had a type I morphology at the proximal femur. The proportion of type III morphology was larger in the proximal femur (41%) than in the other locations.

The LA axis of the femur did not correspond exactly to the AP axis at all femoral levels. At the distal femur, mean (SD) lateral offset of the LA axis was 5.5° (7.5°) on the left and 8.3° (8.9°) on the right. At the midshaft, mean (SD) medial offset of the LA axis was 3.1° (8.4°) on the left and 1.2° (7.9°) on the right. At the proximal femur, mean (SD) lateral offset of the LA axis was 5.4° (9.2°) on the left and 6.2° (8.3°) on the right. The side-to-side differences were statistically significant for the distal femur and midshaft but not the proximal femur. Table 2 lists the 95% confidence intervals for the mean values. As the range of differences was small (0.7°-2.8°), and the differences may not be clinically detected on gross inspection during surgery, we pooled both sides’ values to arrive at a single mean for each level. The LA axis was offset a mean (SD) of 6.9° (8.3°) laterally at the distal femur, 2.2° (8.2°) medially at the midshaft, and 5.8° (8.6°) laterally at the proximal femur. Figure 5 shows the frequency of distribution of LA axis offset.Offset of the LA axis from the AP axis of the femur was significantly (P < .001) different for each femoral level, even when a multivariate analysis was performed to determine the effect of sex, age, or side. Age and sex had no significant effect on mean offset of LA axis from AP axis.

We compared the mean arc between femoral neck axis and LA axis after referencing both off the PC axis. At the distal femur, mean (SD) arc between these 2 axes was 76.6° (13.1°) on the left and 68.3° (13.6°) on the right (mean difference, 8.3°); at the midshaft, mean (SD) arc was 85.2° (13.5°) on the left and 77.9° (13.1°) on the right (mean difference, 7.4°); at the proximal femur, mean (SD) arc was 76.7° (11.9°) on the left and 70.5° (12.8°) on the right (mean difference, 6.2°). The side-to-side differences were statistically significant (P < .001) for all locations.

In multivariate analysis, sex and age did not have an effect on mean arc between the 2 axes. Side and femoral level, however, had a significant effect (P < .001).

Discussion

In total hip arthroplasty, the goal is to restore femoral anteversion, usually referenced to the remaining femoral neck segment.³ In total knee arthroplasty (TKA), proper rotation preserves normal patellofemoral tracking.⁵ Various landmarks are used, such as the PCs or the epicondyles. After tumor resections, these landmarks are often lost.⁶ However, there are no reports of studies validating a particular method of achieving proper rotational orientation of tumor endoprostheses, though several methods are being used. One method involves inserting 2 drill bits before osteotomy—one proximal to the intended level of resection on the anterior femur, and the other on the anterior tibial shaft. The straight line formed can establish a plane of rotation (and length), which the surgeon must aim to restore when the components are placed. This method is useful for distal femur resections but not proximal femur resections. Another method, based on the LA’s anatomical position on the posterior aspect of the femur,⁴ uses the prominence of the LA to align the prosthesis. With this method, the LA is assumed to be directly posterior (6 o’clock) on the femur. However, this assumption has not been confirmed by any study. A third method, described by Heck and Carnesale,⁵ involves marking the anterior aspect of the femur after resection and aligning the components to it. The authors cautioned against using the LA as a landmark, saying that its course is highly variable.

The LA is a narrow, elevated length of bone, with medial and lateral lips, that serves as an attachment site for muscles in the posterior thigh. Proximally, the LA presents with lateral, medial, and intermediate lips. In the midshaft, it is often elevated by an underlying bony ridge or pilaster complex. Distally, it diverges into 2 ridges that form the triangular popliteal surface.^1,7 For the LA to be a reliable landmark, first it must be clearly identifiable on viewing a femoral cross-section. The LA that presents with type I or II morphology is distinctly identifiable, and an axis from its apex and bisecting the canal can easily be constructed. In our study, the LA presented with type I or II morphology in 82% of distal femoral sections and 99% of midshaft femoral sections. Therefore, the LA is a conspicuous landmark at these levels. In the proximal femur, 59% had type I or II morphology. Type III morphology could be identified on cross-sections by the persisting prominence of the lateral lip. However, it may be difficult to appreciate the LA with this morphology at surgery.

Once the LA is identified, its normal cross-sectional position must be defined. One way to do this is to establish the relationship of its axis (LA axis) to the true AP axis. Based on mean values, the LA axis is laterally offset 7º at the distal third of the femur, medially offset 2º at the midshaft, and laterally offset 6º at the proximal third. Therefore, for ideal placement with the LA used for orientation, the component must be internally rotated 7º relative to the LA for femoral resection at the distal third, externally rotated 2º for resection at the midshaft, and internally rotated 6º for resection at the proximal third. Studies have demonstrated that joint contact forces and mechanical alignment of the lower limb can be altered with as little as 5º of femoral malrotation.^8,9 Although such a small degree of malrotation is often asymptomatic, it can have long-term effects on soft-tissue tension and patellar tracking.^10,11 Rotating-platform mobile-bearing TKA designs can compensate for femoral malrotation, but they may have little to no effect on patellar tracking.¹² Therefore, we think aligning the components as near as possible to their natural orientation can prove beneficial in long-term patient management.

Another way of defining the normal cross-sectional position of the LA is to relate it to the femoral neck axis. We measured the difference between these 2 axes. Mean differences were 72º (distal femur), 81.5º (midshaft), and 73.5º (proximal third). Mean arc differences at all levels were larger on the left side—a reflection of the femoral neck being less anteverted on that side in our measurements. Standard deviations were smaller for measurements of LA axis offset from AP axis (range, 7.5°-9.2°) than for measurements of arc between LA axis and femoral neck axis (range, 11.9°-13.6°). This finding indicates there is less variation in the former method, making it preferable for defining the cross-sectional position of the LA.

It has been said that the course of the LA is variable, and our data provide confirmation. The LA does not lie directly posterior (6 o’clock), and it does not trace a straight longitudinal course along the posterior femur, as demonstrated by the different LA axis offsets at 3 levels. However, we may still use it as a landmark if we remain aware how much the LA is offset from the AP axis at each femoral level. Figures 6A-6D, which show CT scans of a patient who underwent distal femoral resection and replacement with an endoprosthesis, illustrate how the LA axis was measured before surgery and how proper prosthesis placement was confirmed after surgery.

In hip arthroplasty, restoration of normal femoral version is the reference for endoprosthetic placement. The literature on “normal” femoral anteversion varies with the method used. In a review of studies on CT-measured adult femoral version, reported values ranged from 6.3° to 40°.² Mean femoral version in our study ranged from 8° to 13°. Orthopedics textbooks generally put the value at 10° to 15º, and this seems to be the range that surgeons target.⁶ However, we found a statistically significant mean side-to-side difference of 5.4°. This finding is possibly explained by our large sample—it was larger than the samples used in other studies of CT-measured femoral version. Other studies have found mean side-to-side differences of up to 4.0º.⁵ Another explanation for our finding is that the studies may differ methodologically. The studies that established values for femoral anteversion were based on CT protocols—thinner slices (1-5 mm), use of foot holders to standardize limb rotation, use of 2 axial cuts in proximal femur to establish femoral neck axis^2,13—designed specifically for this measurement. As the CT scans reviewed in our study are not designed for this purpose, errors in femoral version measurement may have been introduced, which may also explain why there is larger variation in measurements of the arc between the LA axis and the femoral neck axis.

Conclusion

The LA does not lie directly on the posterior surface of the femur. It deviates 6.9° laterally at the distal femur, 2.2° medially at the midshaft, and 6.9° laterally at the proximal third. As the LA is an easily identifiable structure on cross-sections of the femoral shaft at the midshaft and distal third of the femur, it may be useful as a rotational landmark for resections at these levels if these deviations are considered during tumor endoprosthetic replacements.

The distal or proximal femur with tumor endoprosthesis is commonly replaced after segmental resections for bone tumors, complex trauma, or revision arthroplasty. In conventional joint replacements, correct rotational alignment of the component is referenced off anatomical landmarks in the proximal or distal femur. After tumor resection, however, these landmarks are often not available for rotational orientation. There are no reports of studies validating a particular method of establishing rotation in these cases.

To establish a guide for rotational alignment of tumor endoprostheses, we set out to define the natural location of the linea aspera (LA) based on axial computed tomography (CT) scans. The LA is often the most outstanding visible bony landmark on a cross-section of the femur during surgery, and it would be helpful to know its normal orientation in relation to the true anteroposterior (AP) axis of the femur and to the femoral version. We wanted to answer these 5 questions:

1. Is the prominence of the LA easily identifiable on cross-section at different levels of the femoral shaft?

2. Does an axis passing through the LA correspond to the AP axis of the femur?

3. If not, is this axis offset internally or externally and by how much?

4. Is this offset constant at all levels of the femoral shaft?

5. How does the LA axis relate to the femoral neck axis at these levels?

The answers determine if the LA can be reliably used for rotational alignment of tumor endoprostheses.

Materials and Methods

After this study received Institutional Review Board approval, we retrospectively reviewed whole-body fluorine-18-deoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) studies performed in our hospital between 2003 and 2006 to identify those with full-length bilateral femur CT scans. These scans were available on the hospital’s computerized picture archiving system (General Electric). Patients could be included in the study as long as they were at least 18 years old at time of scan and did not have any pathology that deformed the femur, broke a cortex, or otherwise caused any gross asymmetry of the femur. Of the 72 patients with full-length femur CT scans, 3 were excluded: 1 with a congenital hip dysplasia, 1 with an old, malunited femoral fracture, and 1 who was 15 years old at time of scan.

Axial Slice Selection

For each patient, scout AP films were used to measure femoral shaft length from the top of the greater trochanter to the end of the lateral femoral condyle. The levels of the proximal third, midshaft, and distal third were then calculated based on this length. The LA was studied on the axial slices nearest these levels. Next, we scrolled through the scans to identify an axial slice that best showed the femoral neck axis. The literature on CT measurement of femoral anteversion is varied. Some articles describe a technique that uses 2 superimposed axial slices, and others describe a single axial slice.^1-3 We used 1 axial slice to draw the femoral neck axis because our computer software could not superimpose 2 images on 1 screen and because the CT scans were not made under specific protocols to measure anteversion but rather were part of a cancer staging work-up. Axial cuts were made at 5-mm intervals, and not all scans included a single slice capturing the head, neck, and greater trochanter. Therefore, we used a (previously described) method in which the femoral neck axis is drawn on a slice that most captured the femoral neck, usually toward its base.4 Last, in order to draw the posterior condyle (PC) axis, we selected an axial slice that showed the posterior-most aspects of the femoral condyles at the intercondylar notch.

Determining Anteroposterior and Posterior Condyle Axes of Femur

As we made all measurements for each femur off a single CT scan, we were able to use a straight horizontal line—drawn on-screen with a software tool—as a reference for measuring rotation. On a distal femur cut, the PC axis is drawn by connecting the posterior-most points of both condyles. The software calculates the angle formed—the PC angle (Figure 1). This angle, the degree to which the PC axis deviates from a straight horizontal line on-screen, can be used to account for gross rotation of the limb on comparison of images. The AP axis of the femur is the axis perpendicular to the PC axis. As such, the PC angle can also be used to determine degree of deviation of the AP axis from a straight vertical line on-screen. The AP axis was used when calculating the LA axis at the various levels of the femur (Figure 2).

Femoral Version

We used the software tool to draw the femoral neck axis. From the end of this line, a straight horizontal line is drawn on-screen (Figure 3). The software calculates the angle formed—the femoral neck axis angle. We assigned a positive value for a femoral head that pointed anteriorly on the image and a negative value for a head that pointed posteriorly. Adjusting for external rotation of the limb involved calculating the femoral version by subtracting the PC angle from the neck axis angle; adjusting for internal rotation involved adding these 2 angles.

Linea Aspera Morphology

After viewing the first 20 CT scans, we identified 3 types of LA morphology. Type I presents as a thickening on the posterior cortex with a sharp apex; type II presents as a flat-faced but distinct ridge of bone between the medial and lateral lips; and in type III there is no distinct cortical thickening with blunted medial and lateral lips; the latter is always more prominent.

Linea Aspera Axis Offset

From the most posterior point of the LA, a line drawn forward bisecting the femoral canal defined the LA axis. In type I morphology, the posterior-most point was the apex; in type II, the middle of flat posterior surface was used as the starting point; in type III, the lateral lip was used, as it was sharper than the medial lip. This line is again referenced with a straight horizontal line across the image. The PC angle is then added to account for limb rotation, and the result is the LA angle. As the AP axis is perpendicular to the PC axis, the LA angle is subtracted from 90°; the difference represents the amount of offset of the LA axis from the AP axis. By convention, we assigned this a positive value for an LA lateral to the midpoint of the femur and a negative value for an LA medial to the midpoint (Figure 4).

Linea Aspera Axis and Femoral Neck Axis

The angle between the LA axis and the PC axis was measured. The femoral version angle was subtracted from that angle to obtain the arc between the LA axis and the femoral neck axis.

Statistical Analyses

All analyses were performed with SAS 9.1 (SAS Institute). All tests were 2-sided and conducted at the .05 significance level. No adjustments were made for multiple testing. Statistical analysis was performed with nonparametric tests and without making assumptions about the distribution of the study population. Univariate analyses were performed to test for significant side-to-side differences in femoral length, femoral version angle, and LA torsion angles at each level. A multivariate analysis was performed to test for interactions between sex, side, and level. In all analyses, P < .05 was used as the cutoff value for statistical significance.

Results

Femoral lengths varied by side and sex. The left side was longer than the right by a mean of 1.3 mm (P = .008). With multivariate analysis taking into account sex and age (cumulated per decade), there was still a significant effect of side on femoral length. Sex also had a significant effect on femoral length, with females’ femurs shorter by 21.7 mm (standard error, 5.0 mm). Mean (SD) anteversion of the femoral neck was 7.9° (12.7°) on the left and 13.3° (13.0°) on the right; the difference between sides was significant (P < .001). In a multivariate analysis performed to identify potential predictors of femoral version, side still had a significant (P < .001) independent effect; sex and age did not have an effect.

LA morphology varied according to femoral shaft level (Table 1). The morphology was type I in 75% of patients at the distal femur and 74% of patients at the midshaft femur, while only 53% of patients had a type I morphology at the proximal femur. The proportion of type III morphology was larger in the proximal femur (41%) than in the other locations.

The LA axis of the femur did not correspond exactly to the AP axis at all femoral levels. At the distal femur, mean (SD) lateral offset of the LA axis was 5.5° (7.5°) on the left and 8.3° (8.9°) on the right. At the midshaft, mean (SD) medial offset of the LA axis was 3.1° (8.4°) on the left and 1.2° (7.9°) on the right. At the proximal femur, mean (SD) lateral offset of the LA axis was 5.4° (9.2°) on the left and 6.2° (8.3°) on the right. The side-to-side differences were statistically significant for the distal femur and midshaft but not the proximal femur. Table 2 lists the 95% confidence intervals for the mean values. As the range of differences was small (0.7°-2.8°), and the differences may not be clinically detected on gross inspection during surgery, we pooled both sides’ values to arrive at a single mean for each level. The LA axis was offset a mean (SD) of 6.9° (8.3°) laterally at the distal femur, 2.2° (8.2°) medially at the midshaft, and 5.8° (8.6°) laterally at the proximal femur. Figure 5 shows the frequency of distribution of LA axis offset.Offset of the LA axis from the AP axis of the femur was significantly (P < .001) different for each femoral level, even when a multivariate analysis was performed to determine the effect of sex, age, or side. Age and sex had no significant effect on mean offset of LA axis from AP axis.

We compared the mean arc between femoral neck axis and LA axis after referencing both off the PC axis. At the distal femur, mean (SD) arc between these 2 axes was 76.6° (13.1°) on the left and 68.3° (13.6°) on the right (mean difference, 8.3°); at the midshaft, mean (SD) arc was 85.2° (13.5°) on the left and 77.9° (13.1°) on the right (mean difference, 7.4°); at the proximal femur, mean (SD) arc was 76.7° (11.9°) on the left and 70.5° (12.8°) on the right (mean difference, 6.2°). The side-to-side differences were statistically significant (P < .001) for all locations.

In multivariate analysis, sex and age did not have an effect on mean arc between the 2 axes. Side and femoral level, however, had a significant effect (P < .001).

Discussion

In total hip arthroplasty, the goal is to restore femoral anteversion, usually referenced to the remaining femoral neck segment.³ In total knee arthroplasty (TKA), proper rotation preserves normal patellofemoral tracking.⁵ Various landmarks are used, such as the PCs or the epicondyles. After tumor resections, these landmarks are often lost.⁶ However, there are no reports of studies validating a particular method of achieving proper rotational orientation of tumor endoprostheses, though several methods are being used. One method involves inserting 2 drill bits before osteotomy—one proximal to the intended level of resection on the anterior femur, and the other on the anterior tibial shaft. The straight line formed can establish a plane of rotation (and length), which the surgeon must aim to restore when the components are placed. This method is useful for distal femur resections but not proximal femur resections. Another method, based on the LA’s anatomical position on the posterior aspect of the femur,⁴ uses the prominence of the LA to align the prosthesis. With this method, the LA is assumed to be directly posterior (6 o’clock) on the femur. However, this assumption has not been confirmed by any study. A third method, described by Heck and Carnesale,⁵ involves marking the anterior aspect of the femur after resection and aligning the components to it. The authors cautioned against using the LA as a landmark, saying that its course is highly variable.

The LA is a narrow, elevated length of bone, with medial and lateral lips, that serves as an attachment site for muscles in the posterior thigh. Proximally, the LA presents with lateral, medial, and intermediate lips. In the midshaft, it is often elevated by an underlying bony ridge or pilaster complex. Distally, it diverges into 2 ridges that form the triangular popliteal surface.^1,7 For the LA to be a reliable landmark, first it must be clearly identifiable on viewing a femoral cross-section. The LA that presents with type I or II morphology is distinctly identifiable, and an axis from its apex and bisecting the canal can easily be constructed. In our study, the LA presented with type I or II morphology in 82% of distal femoral sections and 99% of midshaft femoral sections. Therefore, the LA is a conspicuous landmark at these levels. In the proximal femur, 59% had type I or II morphology. Type III morphology could be identified on cross-sections by the persisting prominence of the lateral lip. However, it may be difficult to appreciate the LA with this morphology at surgery.

Once the LA is identified, its normal cross-sectional position must be defined. One way to do this is to establish the relationship of its axis (LA axis) to the true AP axis. Based on mean values, the LA axis is laterally offset 7º at the distal third of the femur, medially offset 2º at the midshaft, and laterally offset 6º at the proximal third. Therefore, for ideal placement with the LA used for orientation, the component must be internally rotated 7º relative to the LA for femoral resection at the distal third, externally rotated 2º for resection at the midshaft, and internally rotated 6º for resection at the proximal third. Studies have demonstrated that joint contact forces and mechanical alignment of the lower limb can be altered with as little as 5º of femoral malrotation.^8,9 Although such a small degree of malrotation is often asymptomatic, it can have long-term effects on soft-tissue tension and patellar tracking.^10,11 Rotating-platform mobile-bearing TKA designs can compensate for femoral malrotation, but they may have little to no effect on patellar tracking.¹² Therefore, we think aligning the components as near as possible to their natural orientation can prove beneficial in long-term patient management.

Another way of defining the normal cross-sectional position of the LA is to relate it to the femoral neck axis. We measured the difference between these 2 axes. Mean differences were 72º (distal femur), 81.5º (midshaft), and 73.5º (proximal third). Mean arc differences at all levels were larger on the left side—a reflection of the femoral neck being less anteverted on that side in our measurements. Standard deviations were smaller for measurements of LA axis offset from AP axis (range, 7.5°-9.2°) than for measurements of arc between LA axis and femoral neck axis (range, 11.9°-13.6°). This finding indicates there is less variation in the former method, making it preferable for defining the cross-sectional position of the LA.

It has been said that the course of the LA is variable, and our data provide confirmation. The LA does not lie directly posterior (6 o’clock), and it does not trace a straight longitudinal course along the posterior femur, as demonstrated by the different LA axis offsets at 3 levels. However, we may still use it as a landmark if we remain aware how much the LA is offset from the AP axis at each femoral level. Figures 6A-6D, which show CT scans of a patient who underwent distal femoral resection and replacement with an endoprosthesis, illustrate how the LA axis was measured before surgery and how proper prosthesis placement was confirmed after surgery.

In hip arthroplasty, restoration of normal femoral version is the reference for endoprosthetic placement. The literature on “normal” femoral anteversion varies with the method used. In a review of studies on CT-measured adult femoral version, reported values ranged from 6.3° to 40°.² Mean femoral version in our study ranged from 8° to 13°. Orthopedics textbooks generally put the value at 10° to 15º, and this seems to be the range that surgeons target.⁶ However, we found a statistically significant mean side-to-side difference of 5.4°. This finding is possibly explained by our large sample—it was larger than the samples used in other studies of CT-measured femoral version. Other studies have found mean side-to-side differences of up to 4.0º.⁵ Another explanation for our finding is that the studies may differ methodologically. The studies that established values for femoral anteversion were based on CT protocols—thinner slices (1-5 mm), use of foot holders to standardize limb rotation, use of 2 axial cuts in proximal femur to establish femoral neck axis^2,13—designed specifically for this measurement. As the CT scans reviewed in our study are not designed for this purpose, errors in femoral version measurement may have been introduced, which may also explain why there is larger variation in measurements of the arc between the LA axis and the femoral neck axis.

Conclusion

The LA does not lie directly on the posterior surface of the femur. It deviates 6.9° laterally at the distal femur, 2.2° medially at the midshaft, and 6.9° laterally at the proximal third. As the LA is an easily identifiable structure on cross-sections of the femoral shaft at the midshaft and distal third of the femur, it may be useful as a rotational landmark for resections at these levels if these deviations are considered during tumor endoprosthetic replacements.

The distal or proximal femur with tumor endoprosthesis is commonly replaced after segmental resections for bone tumors, complex trauma, or revision arthroplasty. In conventional joint replacements, correct rotational alignment of the component is referenced off anatomical landmarks in the proximal or distal femur. After tumor resection, however, these landmarks are often not available for rotational orientation. There are no reports of studies validating a particular method of establishing rotation in these cases.

To establish a guide for rotational alignment of tumor endoprostheses, we set out to define the natural location of the linea aspera (LA) based on axial computed tomography (CT) scans. The LA is often the most outstanding visible bony landmark on a cross-section of the femur during surgery, and it would be helpful to know its normal orientation in relation to the true anteroposterior (AP) axis of the femur and to the femoral version. We wanted to answer these 5 questions:

1. Is the prominence of the LA easily identifiable on cross-section at different levels of the femoral shaft?

2. Does an axis passing through the LA correspond to the AP axis of the femur?

3. If not, is this axis offset internally or externally and by how much?

4. Is this offset constant at all levels of the femoral shaft?

5. How does the LA axis relate to the femoral neck axis at these levels?

The answers determine if the LA can be reliably used for rotational alignment of tumor endoprostheses.

Materials and Methods

After this study received Institutional Review Board approval, we retrospectively reviewed whole-body fluorine-18-deoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) studies performed in our hospital between 2003 and 2006 to identify those with full-length bilateral femur CT scans. These scans were available on the hospital’s computerized picture archiving system (General Electric). Patients could be included in the study as long as they were at least 18 years old at time of scan and did not have any pathology that deformed the femur, broke a cortex, or otherwise caused any gross asymmetry of the femur. Of the 72 patients with full-length femur CT scans, 3 were excluded: 1 with a congenital hip dysplasia, 1 with an old, malunited femoral fracture, and 1 who was 15 years old at time of scan.

Axial Slice Selection

For each patient, scout AP films were used to measure femoral shaft length from the top of the greater trochanter to the end of the lateral femoral condyle. The levels of the proximal third, midshaft, and distal third were then calculated based on this length. The LA was studied on the axial slices nearest these levels. Next, we scrolled through the scans to identify an axial slice that best showed the femoral neck axis. The literature on CT measurement of femoral anteversion is varied. Some articles describe a technique that uses 2 superimposed axial slices, and others describe a single axial slice.^1-3 We used 1 axial slice to draw the femoral neck axis because our computer software could not superimpose 2 images on 1 screen and because the CT scans were not made under specific protocols to measure anteversion but rather were part of a cancer staging work-up. Axial cuts were made at 5-mm intervals, and not all scans included a single slice capturing the head, neck, and greater trochanter. Therefore, we used a (previously described) method in which the femoral neck axis is drawn on a slice that most captured the femoral neck, usually toward its base.4 Last, in order to draw the posterior condyle (PC) axis, we selected an axial slice that showed the posterior-most aspects of the femoral condyles at the intercondylar notch.

Determining Anteroposterior and Posterior Condyle Axes of Femur

As we made all measurements for each femur off a single CT scan, we were able to use a straight horizontal line—drawn on-screen with a software tool—as a reference for measuring rotation. On a distal femur cut, the PC axis is drawn by connecting the posterior-most points of both condyles. The software calculates the angle formed—the PC angle (Figure 1). This angle, the degree to which the PC axis deviates from a straight horizontal line on-screen, can be used to account for gross rotation of the limb on comparison of images. The AP axis of the femur is the axis perpendicular to the PC axis. As such, the PC angle can also be used to determine degree of deviation of the AP axis from a straight vertical line on-screen. The AP axis was used when calculating the LA axis at the various levels of the femur (Figure 2).

Femoral Version

We used the software tool to draw the femoral neck axis. From the end of this line, a straight horizontal line is drawn on-screen (Figure 3). The software calculates the angle formed—the femoral neck axis angle. We assigned a positive value for a femoral head that pointed anteriorly on the image and a negative value for a head that pointed posteriorly. Adjusting for external rotation of the limb involved calculating the femoral version by subtracting the PC angle from the neck axis angle; adjusting for internal rotation involved adding these 2 angles.

Linea Aspera Morphology

After viewing the first 20 CT scans, we identified 3 types of LA morphology. Type I presents as a thickening on the posterior cortex with a sharp apex; type II presents as a flat-faced but distinct ridge of bone between the medial and lateral lips; and in type III there is no distinct cortical thickening with blunted medial and lateral lips; the latter is always more prominent.

Linea Aspera Axis Offset

From the most posterior point of the LA, a line drawn forward bisecting the femoral canal defined the LA axis. In type I morphology, the posterior-most point was the apex; in type II, the middle of flat posterior surface was used as the starting point; in type III, the lateral lip was used, as it was sharper than the medial lip. This line is again referenced with a straight horizontal line across the image. The PC angle is then added to account for limb rotation, and the result is the LA angle. As the AP axis is perpendicular to the PC axis, the LA angle is subtracted from 90°; the difference represents the amount of offset of the LA axis from the AP axis. By convention, we assigned this a positive value for an LA lateral to the midpoint of the femur and a negative value for an LA medial to the midpoint (Figure 4).

Linea Aspera Axis and Femoral Neck Axis

The angle between the LA axis and the PC axis was measured. The femoral version angle was subtracted from that angle to obtain the arc between the LA axis and the femoral neck axis.

Statistical Analyses

All analyses were performed with SAS 9.1 (SAS Institute). All tests were 2-sided and conducted at the .05 significance level. No adjustments were made for multiple testing. Statistical analysis was performed with nonparametric tests and without making assumptions about the distribution of the study population. Univariate analyses were performed to test for significant side-to-side differences in femoral length, femoral version angle, and LA torsion angles at each level. A multivariate analysis was performed to test for interactions between sex, side, and level. In all analyses, P < .05 was used as the cutoff value for statistical significance.

Results

Femoral lengths varied by side and sex. The left side was longer than the right by a mean of 1.3 mm (P = .008). With multivariate analysis taking into account sex and age (cumulated per decade), there was still a significant effect of side on femoral length. Sex also had a significant effect on femoral length, with females’ femurs shorter by 21.7 mm (standard error, 5.0 mm). Mean (SD) anteversion of the femoral neck was 7.9° (12.7°) on the left and 13.3° (13.0°) on the right; the difference between sides was significant (P < .001). In a multivariate analysis performed to identify potential predictors of femoral version, side still had a significant (P < .001) independent effect; sex and age did not have an effect.

LA morphology varied according to femoral shaft level (Table 1). The morphology was type I in 75% of patients at the distal femur and 74% of patients at the midshaft femur, while only 53% of patients had a type I morphology at the proximal femur. The proportion of type III morphology was larger in the proximal femur (41%) than in the other locations.

The LA axis of the femur did not correspond exactly to the AP axis at all femoral levels. At the distal femur, mean (SD) lateral offset of the LA axis was 5.5° (7.5°) on the left and 8.3° (8.9°) on the right. At the midshaft, mean (SD) medial offset of the LA axis was 3.1° (8.4°) on the left and 1.2° (7.9°) on the right. At the proximal femur, mean (SD) lateral offset of the LA axis was 5.4° (9.2°) on the left and 6.2° (8.3°) on the right. The side-to-side differences were statistically significant for the distal femur and midshaft but not the proximal femur. Table 2 lists the 95% confidence intervals for the mean values. As the range of differences was small (0.7°-2.8°), and the differences may not be clinically detected on gross inspection during surgery, we pooled both sides’ values to arrive at a single mean for each level. The LA axis was offset a mean (SD) of 6.9° (8.3°) laterally at the distal femur, 2.2° (8.2°) medially at the midshaft, and 5.8° (8.6°) laterally at the proximal femur. Figure 5 shows the frequency of distribution of LA axis offset.Offset of the LA axis from the AP axis of the femur was significantly (P < .001) different for each femoral level, even when a multivariate analysis was performed to determine the effect of sex, age, or side. Age and sex had no significant effect on mean offset of LA axis from AP axis.

We compared the mean arc between femoral neck axis and LA axis after referencing both off the PC axis. At the distal femur, mean (SD) arc between these 2 axes was 76.6° (13.1°) on the left and 68.3° (13.6°) on the right (mean difference, 8.3°); at the midshaft, mean (SD) arc was 85.2° (13.5°) on the left and 77.9° (13.1°) on the right (mean difference, 7.4°); at the proximal femur, mean (SD) arc was 76.7° (11.9°) on the left and 70.5° (12.8°) on the right (mean difference, 6.2°). The side-to-side differences were statistically significant (P < .001) for all locations.

In multivariate analysis, sex and age did not have an effect on mean arc between the 2 axes. Side and femoral level, however, had a significant effect (P < .001).

Discussion

In total hip arthroplasty, the goal is to restore femoral anteversion, usually referenced to the remaining femoral neck segment.³ In total knee arthroplasty (TKA), proper rotation preserves normal patellofemoral tracking.⁵ Various landmarks are used, such as the PCs or the epicondyles. After tumor resections, these landmarks are often lost.⁶ However, there are no reports of studies validating a particular method of achieving proper rotational orientation of tumor endoprostheses, though several methods are being used. One method involves inserting 2 drill bits before osteotomy—one proximal to the intended level of resection on the anterior femur, and the other on the anterior tibial shaft. The straight line formed can establish a plane of rotation (and length), which the surgeon must aim to restore when the components are placed. This method is useful for distal femur resections but not proximal femur resections. Another method, based on the LA’s anatomical position on the posterior aspect of the femur,⁴ uses the prominence of the LA to align the prosthesis. With this method, the LA is assumed to be directly posterior (6 o’clock) on the femur. However, this assumption has not been confirmed by any study. A third method, described by Heck and Carnesale,⁵ involves marking the anterior aspect of the femur after resection and aligning the components to it. The authors cautioned against using the LA as a landmark, saying that its course is highly variable.

The LA is a narrow, elevated length of bone, with medial and lateral lips, that serves as an attachment site for muscles in the posterior thigh. Proximally, the LA presents with lateral, medial, and intermediate lips. In the midshaft, it is often elevated by an underlying bony ridge or pilaster complex. Distally, it diverges into 2 ridges that form the triangular popliteal surface.^1,7 For the LA to be a reliable landmark, first it must be clearly identifiable on viewing a femoral cross-section. The LA that presents with type I or II morphology is distinctly identifiable, and an axis from its apex and bisecting the canal can easily be constructed. In our study, the LA presented with type I or II morphology in 82% of distal femoral sections and 99% of midshaft femoral sections. Therefore, the LA is a conspicuous landmark at these levels. In the proximal femur, 59% had type I or II morphology. Type III morphology could be identified on cross-sections by the persisting prominence of the lateral lip. However, it may be difficult to appreciate the LA with this morphology at surgery.

Once the LA is identified, its normal cross-sectional position must be defined. One way to do this is to establish the relationship of its axis (LA axis) to the true AP axis. Based on mean values, the LA axis is laterally offset 7º at the distal third of the femur, medially offset 2º at the midshaft, and laterally offset 6º at the proximal third. Therefore, for ideal placement with the LA used for orientation, the component must be internally rotated 7º relative to the LA for femoral resection at the distal third, externally rotated 2º for resection at the midshaft, and internally rotated 6º for resection at the proximal third. Studies have demonstrated that joint contact forces and mechanical alignment of the lower limb can be altered with as little as 5º of femoral malrotation.^8,9 Although such a small degree of malrotation is often asymptomatic, it can have long-term effects on soft-tissue tension and patellar tracking.^10,11 Rotating-platform mobile-bearing TKA designs can compensate for femoral malrotation, but they may have little to no effect on patellar tracking.¹² Therefore, we think aligning the components as near as possible to their natural orientation can prove beneficial in long-term patient management.

Another way of defining the normal cross-sectional position of the LA is to relate it to the femoral neck axis. We measured the difference between these 2 axes. Mean differences were 72º (distal femur), 81.5º (midshaft), and 73.5º (proximal third). Mean arc differences at all levels were larger on the left side—a reflection of the femoral neck being less anteverted on that side in our measurements. Standard deviations were smaller for measurements of LA axis offset from AP axis (range, 7.5°-9.2°) than for measurements of arc between LA axis and femoral neck axis (range, 11.9°-13.6°). This finding indicates there is less variation in the former method, making it preferable for defining the cross-sectional position of the LA.

It has been said that the course of the LA is variable, and our data provide confirmation. The LA does not lie directly posterior (6 o’clock), and it does not trace a straight longitudinal course along the posterior femur, as demonstrated by the different LA axis offsets at 3 levels. However, we may still use it as a landmark if we remain aware how much the LA is offset from the AP axis at each femoral level. Figures 6A-6D, which show CT scans of a patient who underwent distal femoral resection and replacement with an endoprosthesis, illustrate how the LA axis was measured before surgery and how proper prosthesis placement was confirmed after surgery.

In hip arthroplasty, restoration of normal femoral version is the reference for endoprosthetic placement. The literature on “normal” femoral anteversion varies with the method used. In a review of studies on CT-measured adult femoral version, reported values ranged from 6.3° to 40°.² Mean femoral version in our study ranged from 8° to 13°. Orthopedics textbooks generally put the value at 10° to 15º, and this seems to be the range that surgeons target.⁶ However, we found a statistically significant mean side-to-side difference of 5.4°. This finding is possibly explained by our large sample—it was larger than the samples used in other studies of CT-measured femoral version. Other studies have found mean side-to-side differences of up to 4.0º.⁵ Another explanation for our finding is that the studies may differ methodologically. The studies that established values for femoral anteversion were based on CT protocols—thinner slices (1-5 mm), use of foot holders to standardize limb rotation, use of 2 axial cuts in proximal femur to establish femoral neck axis^2,13—designed specifically for this measurement. As the CT scans reviewed in our study are not designed for this purpose, errors in femoral version measurement may have been introduced, which may also explain why there is larger variation in measurements of the arc between the LA axis and the femoral neck axis.

Conclusion

The LA does not lie directly on the posterior surface of the femur. It deviates 6.9° laterally at the distal femur, 2.2° medially at the midshaft, and 6.9° laterally at the proximal third. As the LA is an easily identifiable structure on cross-sections of the femoral shaft at the midshaft and distal third of the femur, it may be useful as a rotational landmark for resections at these levels if these deviations are considered during tumor endoprosthetic replacements.

A 55-year-old man presented with a 2-day history of acute first toe pain in his right foot after banging the affected toe on a door. Physical examination demonstrated a swollen first toe with marked tenderness to palpation. Radiographs were obtained (Figures 1a and 1b).

What is the diagnosis? What additional imaging tests may be useful to confirm the diagnosis?

Answer

The radiographs of the right foot excluded fracture as the underlying etiology of the patient’s pain. The findings included soft tissue swelling and periarticular (ie, near but not involving the joint) erosions involving the first metatarsal head (white asterisks, Figure 1c). The erosion on the medial aspect of the metatarsal head had remodeling of bone at the periphery of the erosion, which created the appearance of “overhanging edges” (white arrows, Figure 1c). The radiographic appearance suggests the diagnosis of gouty arthritis.

Gouty arthritis, which is caused by the deposition of monosodium urate crystals in the soft tissues surrounding joints, continues to increase in prevalence—likely due to the growing aging population and risk factors such as obesity and diabetes. Gouty arthritis typically presents as painful episodes of arthritis affecting a single joint that can be extremely tender to touch. Acute attacks typically subside within 5 to 7 days. Acute gout may result in fever and elevated white blood cell counts, making it difficult to distinguish from septic arthritis.¹ While more common in males in the younger population, gout affects men and women equally in patients older than age 60 years.²

While patients with gouty arthritis have hyperuricemia, only approximately 10% develop gout. The American College of Rheumatology’s preliminary criteria² for the diagnosis of gout include the presence of characteristic urate crystals in the joint fluid of the affected joint during the attack, the presence of a tophus (soft tissue mass containing urate crystals), or at least six of the following:

• More than one attack of acute arthritis
• Maximum joint inflammation developed within 1 day
• Monoarticular arthritis
• Redness of the joint
• First metatarsophalangeal (MTP) joint pain/swelling
• Unilateral first MTP joint attack
• Unilateral tarsal joint attack
• Suspected tophus
• Hyperuricemia
• Asymmetrical swelling of the joint on radiography
• Subcortical cysts without erosions on radiography
• Joint fluid culture negative during an attack.

As highlighted by the criteria, the first MTP joint is a common location for gouty arthritis, and is referred to as podagra. A meta-analysis published in 2016 reports that an estimated 73% of patients with gout will have involvement of the first MTP.³

Regarding imaging studies, radiography is often the first imaging test performed to evaluate for gout, and can reveal characteristic findings such as periarticular erosions with sclerotic margins, overhanging edges of remodeling bone, and adjacent soft tissue tophi. These findings, however, occur late in the disease. Ultrasound may be useful for earlier diagnosis with the “double contour sign,” which is a specific finding representing the appearance of urate crystals deposited on the hyaline cartilage of the joint. Dual-energy computed tomography (CT) has been shown to not only demonstrate early erosions and soft tissue tophi, but also to characterize the crystals, making CT a highly sensitive and specific test for the detection of gouty arthritis.⁴

Treatment of acute episodes of gout includes nonsteroidal anti-inflammatory agents, colchicine, and corticosteroids. Early diagnosis and treatment can prevent progression to advanced arthritis and chronic impairment.

A 55-year-old man presented with a 2-day history of acute first toe pain in his right foot after banging the affected toe on a door. Physical examination demonstrated a swollen first toe with marked tenderness to palpation. Radiographs were obtained (Figures 1a and 1b).

What is the diagnosis? What additional imaging tests may be useful to confirm the diagnosis?

Answer

The radiographs of the right foot excluded fracture as the underlying etiology of the patient’s pain. The findings included soft tissue swelling and periarticular (ie, near but not involving the joint) erosions involving the first metatarsal head (white asterisks, Figure 1c). The erosion on the medial aspect of the metatarsal head had remodeling of bone at the periphery of the erosion, which created the appearance of “overhanging edges” (white arrows, Figure 1c). The radiographic appearance suggests the diagnosis of gouty arthritis.

Gouty arthritis, which is caused by the deposition of monosodium urate crystals in the soft tissues surrounding joints, continues to increase in prevalence—likely due to the growing aging population and risk factors such as obesity and diabetes. Gouty arthritis typically presents as painful episodes of arthritis affecting a single joint that can be extremely tender to touch. Acute attacks typically subside within 5 to 7 days. Acute gout may result in fever and elevated white blood cell counts, making it difficult to distinguish from septic arthritis.¹ While more common in males in the younger population, gout affects men and women equally in patients older than age 60 years.²

While patients with gouty arthritis have hyperuricemia, only approximately 10% develop gout. The American College of Rheumatology’s preliminary criteria² for the diagnosis of gout include the presence of characteristic urate crystals in the joint fluid of the affected joint during the attack, the presence of a tophus (soft tissue mass containing urate crystals), or at least six of the following:

• More than one attack of acute arthritis
• Maximum joint inflammation developed within 1 day
• Monoarticular arthritis
• Redness of the joint
• First metatarsophalangeal (MTP) joint pain/swelling
• Unilateral first MTP joint attack
• Unilateral tarsal joint attack
• Suspected tophus
• Hyperuricemia
• Asymmetrical swelling of the joint on radiography
• Subcortical cysts without erosions on radiography
• Joint fluid culture negative during an attack.

As highlighted by the criteria, the first MTP joint is a common location for gouty arthritis, and is referred to as podagra. A meta-analysis published in 2016 reports that an estimated 73% of patients with gout will have involvement of the first MTP.³

Regarding imaging studies, radiography is often the first imaging test performed to evaluate for gout, and can reveal characteristic findings such as periarticular erosions with sclerotic margins, overhanging edges of remodeling bone, and adjacent soft tissue tophi. These findings, however, occur late in the disease. Ultrasound may be useful for earlier diagnosis with the “double contour sign,” which is a specific finding representing the appearance of urate crystals deposited on the hyaline cartilage of the joint. Dual-energy computed tomography (CT) has been shown to not only demonstrate early erosions and soft tissue tophi, but also to characterize the crystals, making CT a highly sensitive and specific test for the detection of gouty arthritis.⁴

Treatment of acute episodes of gout includes nonsteroidal anti-inflammatory agents, colchicine, and corticosteroids. Early diagnosis and treatment can prevent progression to advanced arthritis and chronic impairment.

A 55-year-old man presented with a 2-day history of acute first toe pain in his right foot after banging the affected toe on a door. Physical examination demonstrated a swollen first toe with marked tenderness to palpation. Radiographs were obtained (Figures 1a and 1b).

What is the diagnosis? What additional imaging tests may be useful to confirm the diagnosis?

Answer

The radiographs of the right foot excluded fracture as the underlying etiology of the patient’s pain. The findings included soft tissue swelling and periarticular (ie, near but not involving the joint) erosions involving the first metatarsal head (white asterisks, Figure 1c). The erosion on the medial aspect of the metatarsal head had remodeling of bone at the periphery of the erosion, which created the appearance of “overhanging edges” (white arrows, Figure 1c). The radiographic appearance suggests the diagnosis of gouty arthritis.

Gouty arthritis, which is caused by the deposition of monosodium urate crystals in the soft tissues surrounding joints, continues to increase in prevalence—likely due to the growing aging population and risk factors such as obesity and diabetes. Gouty arthritis typically presents as painful episodes of arthritis affecting a single joint that can be extremely tender to touch. Acute attacks typically subside within 5 to 7 days. Acute gout may result in fever and elevated white blood cell counts, making it difficult to distinguish from septic arthritis.¹ While more common in males in the younger population, gout affects men and women equally in patients older than age 60 years.²

While patients with gouty arthritis have hyperuricemia, only approximately 10% develop gout. The American College of Rheumatology’s preliminary criteria² for the diagnosis of gout include the presence of characteristic urate crystals in the joint fluid of the affected joint during the attack, the presence of a tophus (soft tissue mass containing urate crystals), or at least six of the following:

• More than one attack of acute arthritis
• Maximum joint inflammation developed within 1 day
• Monoarticular arthritis
• Redness of the joint
• First metatarsophalangeal (MTP) joint pain/swelling
• Unilateral first MTP joint attack
• Unilateral tarsal joint attack
• Suspected tophus
• Hyperuricemia
• Asymmetrical swelling of the joint on radiography
• Subcortical cysts without erosions on radiography
• Joint fluid culture negative during an attack.

As highlighted by the criteria, the first MTP joint is a common location for gouty arthritis, and is referred to as podagra. A meta-analysis published in 2016 reports that an estimated 73% of patients with gout will have involvement of the first MTP.³

Regarding imaging studies, radiography is often the first imaging test performed to evaluate for gout, and can reveal characteristic findings such as periarticular erosions with sclerotic margins, overhanging edges of remodeling bone, and adjacent soft tissue tophi. These findings, however, occur late in the disease. Ultrasound may be useful for earlier diagnosis with the “double contour sign,” which is a specific finding representing the appearance of urate crystals deposited on the hyaline cartilage of the joint. Dual-energy computed tomography (CT) has been shown to not only demonstrate early erosions and soft tissue tophi, but also to characterize the crystals, making CT a highly sensitive and specific test for the detection of gouty arthritis.⁴

Treatment of acute episodes of gout includes nonsteroidal anti-inflammatory agents, colchicine, and corticosteroids. Early diagnosis and treatment can prevent progression to advanced arthritis and chronic impairment.