Case Reports

Intraneural ganglion cysts of peripheral nerves occurring within the epineural sheath are rare.^1-7 Case reports exist primarily within the neurosurgical literature, but very little in the orthopedic literature describes this condition. The peripheral nerve most commonly affected by an intraneural ganglion is the common peroneal nerve (CPN).^2,8,9 Such ganglia most often afflict middle-aged men with a history of micro- or macro-trauma and present with typical clinical manifestations of calf pain and progressive symptoms of ipsilateral foot drop and lower leg paresthesia.^2-5,10-12 The mechanism by which these ganglia form is not well understood and, as a result, treatment options are debated.⁶ Recent development of a “unified articular theory,” suggests that such intraneural ganglia of the CPN are fed by a small, recurrent articular branch of the CPN.^6,12,13 Cadaveric studies indicate that this branch originates from the deep peroneal nerve, just millimeters distal to the bifurcation of the CPN, and extends to the superior tibiofibular joint, providing direct access for cyst fluid to enter the CPN following the path of least resistance.^7,8,12,14 Therefore, according to the unified articular theory, the recommended treatment involves division of the articular branch, allowing the ganglion to be decompressed.⁶

We present a case of a 41-year-old man with an intraneural ganglion cyst of the CPN who was successfully treated, according to the recommendations of the unified articular theory. It is important for orthopedic surgeons to read about and recognize this condition, because knowledge of the operative technique outlined in our report allows it to be treated quite effectively. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 41-year-old man presented with a 2-month history of traumatic left lateral knee pain with numbness and weakness to the left foot and ankle. Initial examination showed a mild restriction of lumbosacral range of motion, with no complaints of lower back pain. Sciatic root stretch signs were negative. Strength testing of the lower extremities revealed 3+/5 strength of ankle dorsiflexion and great toe extension on the left side. There was a mild alteration in sensation to light touch on the lateral side of the left foot. Tenderness, without swelling, was present around the left fibular head. There was a positive Tinel sign over the peroneal nerve at the level of the fibular neck.

The patient was initially treated with anti-inflammatories and activity modification. An electromyogram (EMG)/nerve conduction study of the lower extremity showed a left peroneal nerve neurapraxia at the level of the fibular head. Noncontrast magnetic resonance imaging (MRI) of the left knee showed a “slightly prominent vein coursing posterior to the fibular head near the expected location of the common peroneal nerve,” according to the radiologist’s notes (Figure 1). The patient exhibited improvement with use of anti-inflammatories over several months. There was an increase in his ankle dorsiflexion strength to 4/5 and improvement in his pain and numbness.

Approximately 7 months after his initial presentation, the patient developed a marked worsening—increased numbness and weakness to ankle dorsiflexion—of his original symptoms. A repeat EMG/nerve conduction study of the lower extremity showed a persistent peroneal nerve neuropathy with a persistent denervation of the extensor hallucis longus, tibialis anterior, and extensor digitorum brevis muscles.

Because of continuing symptoms and increasing pain, the patient had surgery 8 months after his initial presentation. At that time, a markedly thickened peroneal nerve was identified. An incision in the epineural sheath released a clear gelatinous fluid consistent with a ganglion cyst. Through the epineural incision, the nerve was decompressed by manually “milking” the fluid from within the sheath. Approximately  30 mL of mucinous fluid was obtained and sent to pathology. No cells were identified.

Postoperatively, the patient noted a marked improvement in his pain. By 2 weeks postoperatively, the numbness in his foot had resolved. At 6 weeks after surgery, the strength of his tibialis anterior and extensor hallucis longus muscles had improved from 3+ to 4-, and he was free of pain.

At 2 months postoperatively, the patient redeveloped pain and numbness, and noted progressive weakness of his left foot and ankle. A repeat MRI of the left knee showed a dilated tubular structure corresponding to the course of the CPN. Comparison of this MRI with the initial MRI showed that the “prominent vein” was actually the dilated CPN.

He was taken to the operating room again 5 months after his first operation. At this time, the CPN was again noted to be markedly dilated (Figure 2). The nerve was explored and a recurrent branch to the proximal tibiofibular joint was identified and divided (Figures 3, 4). Through the divided branch, the CPN could be decompressed by manually “milking” the nerve in a proximal-to-distal direction, expressing clear gelatinous fluid consistent with a ganglion cyst (Figure 5). Pathology of the excised portion of the recurrent nerve was consistent with an intraneural ganglion cyst.

By 2 weeks postoperatively, the numbness of the patient’s left foot had completely resolved, as did his pain. By 3 months after surgery, his extensor hallucis longus strength was 5/5, and ankle dorsiflexion was 4-/5. At 6 months, his ankle dorsiflexion strength was 5/5, and he was completely asymptomatic. At 2 years postoperatively, he remained completely asymptomatic. A follow-up MRI of the left knee showed a ganglion cyst present at the proximal tibiofibular joint with resolution of the intraneural ganglion cyst within the CPN (Figure 6).

Discussion

Intraneural ganglia of peripheral nerves are relatively rare, most commonly occurring in the CPN.^6,8,9 A literature search reveals that this condition is only sparsely reported in orthopedic journals. This report, therefore, describes this rare, yet curable, condition. As noted, without appropriate intervention, the condition has a high likelihood of recurrence with only a brief interruption of symptoms.^6,8,9,12

The operative technique delineated in this report relies heavily on research demonstrating that peroneal intraneural ganglia develop from the superior tibiofibular joint and gain access to the CPN via the recurrent articular branch.^8,13 Research indicates that such ganglia preferentially proceed proximally along the deep portion of the CPN, within the epineurium.⁶ This hypothesis was corroborated in our case by the swollen appearance of the CPN proximal to its bifurcation.

Currently, there is no consensus on treatment of intraneural ganglion cysts of the CPN. However, evidence suggests that disconnection of the recurrent branch of the CPN may be important in successfully treating the condition.^6,9,14 This unified articular theory was initially proposed by Spinner and colleagues¹² in 2003 and recommends that surgical treatment focus on the articular branch as the source of cyst fluid.^6,9,12,14 This theory by Spinner and coauthors^12,14 was substantiated in our case: Once the articular branch was disconnected, cyst fluid was easily expressed via antegrade massage through the disconnected end. Pathologic analysis of a portion of the detached articular branch is also recommended to rule out other cystic lesions, such as cystic shwannomas.¹⁴

The history of the unified articular theory began in the mid-1990s, when Dr. Robert Spinner, board certified in both orthopedic and neurologic surgery, began researching causes of intraneural ganglion cysts. At the time, such ganglia were often treated by radical resection of the nerve and the cyst. Based on his review of literature, and his own cases, Spinner¹⁵ developed the theory that, just as with extraneural ganglia, these cysts are fed by fluid from the joint. According to Spinner,⁹ the sources of such connections were very small articular nerve branches that connect the nerve to the joint. His research led him to the original citation of such an intraneural ganglion of the ulnar nerve, first described by Dr. M. Beauchene, a French physician, in 1810.¹⁶ Spinner also discovered that Beauchene’s original dissection specimen had been preserved and was displayed in a medical museum in Paris. When Spinner went to France to view the specimen, he indeed found an intraneural ganglion of the ulnar nerve. On closer inspection, Spinner also discovered a small articular nerve branch containing a “hollow lumen” that would have been capable of allowing the passage of fluid into the nerve and leading to the development of a cyst.¹⁶

In our case, in the first operation, a simple incisional decompression of the CPN was performed. Unfortunately, the ganglion cyst quickly recurred, as did the patient’s symptoms. In the second surgical procedure, the articular branch connecting the peroneal nerve to the proximal tibiofibular joint was incised and disconnected from the nerve. This allowed the nerve to be decompressed and prevented a recurrence of the ganglion cyst within the nerve with complete resolution of the patient’s symptoms. This difference alone most likely accounts for the rapid recurrence of symptoms after the initial operation, since the fluid was simply drained, but the source was not detached, allowing the ganglion to recur.^6,12,14 This is similar in theory to excising the attachment of a ganglion cyst at the wrist from the underlying joint capsule rather than performing a needle aspiration or puncturing of the cyst.¹²

Regarding the imaging techniques used to identify intraneural ganglia, it is essential that the surgeon be aware of the unified articular theory and the likely presence of an articular branch. Such branches are extremely small and may be easily missed on imaging and intraoperatively.^17,18 MRI is the best method to image these cysts because of its superior ability to visualize soft-tissue lesions.^18,19 Intraneural ganglion cysts typically appear as homogenous, lobulated, well-circumscribed masses that are hyperintense on T2-weighted MRI.^3,19 Gadolinium may also offer diagnostic utility, because these masses do not enhance with its use on T1-weighted MRI.^3,17,19 By employing these techniques, one may easily view most of the ganglion cyst. To image the small articular branch, Spinner and colleagues¹⁷ recommend thin-section images with high–spatial resolution T2-imaging. They also advocate obtaining multiple image views and planes to increase the likelihood of successful imaging.¹⁷ 

The applications of the unified articular theory also extend beyond intraneural ganglia of the CPN. While the CPN is the most common location for intraneural ganglion occurrence,^6,17,20 cases have also been described of intraneural ganglion cysts of the tibial nerve at the proximal tibiofibular joint, as well as via the posterior tibial and medial plantar nerves at the subtalar joint within the tarsal tunnel.^11,18-23 Most cases involving the posterior tibial and medial plantar nerves were found in patients presenting with signs of tarsal tunnel syndrome.^22,23 Intraneural ganglia have also been found within the superficial peroneal nerve arising from the inferior tibiofibular joint.²⁰ In certain cases, these ganglia have also been noted to connect to the joint via a small articular branch.^19,22 In 1 case of an intraneural ganglion of the tibial nerve at the superior tibiofibular joint, initial conservative surgery led to early recurrence of symptoms.¹⁹ Just as in our case, the patient returned to the operating room and, after isolation and ligation of an articular branch, the patient experienced long-term resolution of both the symptoms and the cyst.¹⁹

Given the overwhelming evidence in support of the unified articular theory, we agree with the recommendation by Spinner and colleagues¹⁹ to search for an articular branch both via preoperative imaging and during the operation itself in all cases of intraneural ganglia. Assuming the mechanism of cyst formation is the same in most cases of intraneural ganglia, one could reasonably apply the same surgical techniques used in our case to the management of all intraneural ganglia, drastically reducing recurrence rates.

Conclusion

Based on research and corroborated by this case, the key to successful operative treatment of a common peroneal intraneural ganglion is division of the recurrent articular branch, which connects the proximal tibiofibular joint to the CPN.^6,9,11,12,14 Evidence has shown that disconnecting the articular branch and disrupting the source of the intraneural ganglion can resolve the condition and dramatically diminish the chance of recurrence.^6,8,12,14 This has become known as the unified articular theory.^6,12,14 Reports also suggest that, without disconnecting this articular branch, intraneural ganglion recurrence rates may be higher than 30%.^6,12,14,19 This case, therefore, supports the findings of previous authors^9-11,14 and provides an example of successful utilization of the treatment protocol delineated by Spinner and colleagues.^10,11

Intraneural ganglion cysts of peripheral nerves occurring within the epineural sheath are rare.^1-7 Case reports exist primarily within the neurosurgical literature, but very little in the orthopedic literature describes this condition. The peripheral nerve most commonly affected by an intraneural ganglion is the common peroneal nerve (CPN).^2,8,9 Such ganglia most often afflict middle-aged men with a history of micro- or macro-trauma and present with typical clinical manifestations of calf pain and progressive symptoms of ipsilateral foot drop and lower leg paresthesia.^2-5,10-12 The mechanism by which these ganglia form is not well understood and, as a result, treatment options are debated.⁶ Recent development of a “unified articular theory,” suggests that such intraneural ganglia of the CPN are fed by a small, recurrent articular branch of the CPN.^6,12,13 Cadaveric studies indicate that this branch originates from the deep peroneal nerve, just millimeters distal to the bifurcation of the CPN, and extends to the superior tibiofibular joint, providing direct access for cyst fluid to enter the CPN following the path of least resistance.^7,8,12,14 Therefore, according to the unified articular theory, the recommended treatment involves division of the articular branch, allowing the ganglion to be decompressed.⁶

We present a case of a 41-year-old man with an intraneural ganglion cyst of the CPN who was successfully treated, according to the recommendations of the unified articular theory. It is important for orthopedic surgeons to read about and recognize this condition, because knowledge of the operative technique outlined in our report allows it to be treated quite effectively. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 41-year-old man presented with a 2-month history of traumatic left lateral knee pain with numbness and weakness to the left foot and ankle. Initial examination showed a mild restriction of lumbosacral range of motion, with no complaints of lower back pain. Sciatic root stretch signs were negative. Strength testing of the lower extremities revealed 3+/5 strength of ankle dorsiflexion and great toe extension on the left side. There was a mild alteration in sensation to light touch on the lateral side of the left foot. Tenderness, without swelling, was present around the left fibular head. There was a positive Tinel sign over the peroneal nerve at the level of the fibular neck.

The patient was initially treated with anti-inflammatories and activity modification. An electromyogram (EMG)/nerve conduction study of the lower extremity showed a left peroneal nerve neurapraxia at the level of the fibular head. Noncontrast magnetic resonance imaging (MRI) of the left knee showed a “slightly prominent vein coursing posterior to the fibular head near the expected location of the common peroneal nerve,” according to the radiologist’s notes (Figure 1). The patient exhibited improvement with use of anti-inflammatories over several months. There was an increase in his ankle dorsiflexion strength to 4/5 and improvement in his pain and numbness.

Approximately 7 months after his initial presentation, the patient developed a marked worsening—increased numbness and weakness to ankle dorsiflexion—of his original symptoms. A repeat EMG/nerve conduction study of the lower extremity showed a persistent peroneal nerve neuropathy with a persistent denervation of the extensor hallucis longus, tibialis anterior, and extensor digitorum brevis muscles.

Because of continuing symptoms and increasing pain, the patient had surgery 8 months after his initial presentation. At that time, a markedly thickened peroneal nerve was identified. An incision in the epineural sheath released a clear gelatinous fluid consistent with a ganglion cyst. Through the epineural incision, the nerve was decompressed by manually “milking” the fluid from within the sheath. Approximately  30 mL of mucinous fluid was obtained and sent to pathology. No cells were identified.

Postoperatively, the patient noted a marked improvement in his pain. By 2 weeks postoperatively, the numbness in his foot had resolved. At 6 weeks after surgery, the strength of his tibialis anterior and extensor hallucis longus muscles had improved from 3+ to 4-, and he was free of pain.

At 2 months postoperatively, the patient redeveloped pain and numbness, and noted progressive weakness of his left foot and ankle. A repeat MRI of the left knee showed a dilated tubular structure corresponding to the course of the CPN. Comparison of this MRI with the initial MRI showed that the “prominent vein” was actually the dilated CPN.

He was taken to the operating room again 5 months after his first operation. At this time, the CPN was again noted to be markedly dilated (Figure 2). The nerve was explored and a recurrent branch to the proximal tibiofibular joint was identified and divided (Figures 3, 4). Through the divided branch, the CPN could be decompressed by manually “milking” the nerve in a proximal-to-distal direction, expressing clear gelatinous fluid consistent with a ganglion cyst (Figure 5). Pathology of the excised portion of the recurrent nerve was consistent with an intraneural ganglion cyst.

By 2 weeks postoperatively, the numbness of the patient’s left foot had completely resolved, as did his pain. By 3 months after surgery, his extensor hallucis longus strength was 5/5, and ankle dorsiflexion was 4-/5. At 6 months, his ankle dorsiflexion strength was 5/5, and he was completely asymptomatic. At 2 years postoperatively, he remained completely asymptomatic. A follow-up MRI of the left knee showed a ganglion cyst present at the proximal tibiofibular joint with resolution of the intraneural ganglion cyst within the CPN (Figure 6).

Discussion

Intraneural ganglia of peripheral nerves are relatively rare, most commonly occurring in the CPN.^6,8,9 A literature search reveals that this condition is only sparsely reported in orthopedic journals. This report, therefore, describes this rare, yet curable, condition. As noted, without appropriate intervention, the condition has a high likelihood of recurrence with only a brief interruption of symptoms.^6,8,9,12

The operative technique delineated in this report relies heavily on research demonstrating that peroneal intraneural ganglia develop from the superior tibiofibular joint and gain access to the CPN via the recurrent articular branch.^8,13 Research indicates that such ganglia preferentially proceed proximally along the deep portion of the CPN, within the epineurium.⁶ This hypothesis was corroborated in our case by the swollen appearance of the CPN proximal to its bifurcation.

Currently, there is no consensus on treatment of intraneural ganglion cysts of the CPN. However, evidence suggests that disconnection of the recurrent branch of the CPN may be important in successfully treating the condition.^6,9,14 This unified articular theory was initially proposed by Spinner and colleagues¹² in 2003 and recommends that surgical treatment focus on the articular branch as the source of cyst fluid.^6,9,12,14 This theory by Spinner and coauthors^12,14 was substantiated in our case: Once the articular branch was disconnected, cyst fluid was easily expressed via antegrade massage through the disconnected end. Pathologic analysis of a portion of the detached articular branch is also recommended to rule out other cystic lesions, such as cystic shwannomas.¹⁴

The history of the unified articular theory began in the mid-1990s, when Dr. Robert Spinner, board certified in both orthopedic and neurologic surgery, began researching causes of intraneural ganglion cysts. At the time, such ganglia were often treated by radical resection of the nerve and the cyst. Based on his review of literature, and his own cases, Spinner¹⁵ developed the theory that, just as with extraneural ganglia, these cysts are fed by fluid from the joint. According to Spinner,⁹ the sources of such connections were very small articular nerve branches that connect the nerve to the joint. His research led him to the original citation of such an intraneural ganglion of the ulnar nerve, first described by Dr. M. Beauchene, a French physician, in 1810.¹⁶ Spinner also discovered that Beauchene’s original dissection specimen had been preserved and was displayed in a medical museum in Paris. When Spinner went to France to view the specimen, he indeed found an intraneural ganglion of the ulnar nerve. On closer inspection, Spinner also discovered a small articular nerve branch containing a “hollow lumen” that would have been capable of allowing the passage of fluid into the nerve and leading to the development of a cyst.¹⁶

In our case, in the first operation, a simple incisional decompression of the CPN was performed. Unfortunately, the ganglion cyst quickly recurred, as did the patient’s symptoms. In the second surgical procedure, the articular branch connecting the peroneal nerve to the proximal tibiofibular joint was incised and disconnected from the nerve. This allowed the nerve to be decompressed and prevented a recurrence of the ganglion cyst within the nerve with complete resolution of the patient’s symptoms. This difference alone most likely accounts for the rapid recurrence of symptoms after the initial operation, since the fluid was simply drained, but the source was not detached, allowing the ganglion to recur.^6,12,14 This is similar in theory to excising the attachment of a ganglion cyst at the wrist from the underlying joint capsule rather than performing a needle aspiration or puncturing of the cyst.¹²

Regarding the imaging techniques used to identify intraneural ganglia, it is essential that the surgeon be aware of the unified articular theory and the likely presence of an articular branch. Such branches are extremely small and may be easily missed on imaging and intraoperatively.^17,18 MRI is the best method to image these cysts because of its superior ability to visualize soft-tissue lesions.^18,19 Intraneural ganglion cysts typically appear as homogenous, lobulated, well-circumscribed masses that are hyperintense on T2-weighted MRI.^3,19 Gadolinium may also offer diagnostic utility, because these masses do not enhance with its use on T1-weighted MRI.^3,17,19 By employing these techniques, one may easily view most of the ganglion cyst. To image the small articular branch, Spinner and colleagues¹⁷ recommend thin-section images with high–spatial resolution T2-imaging. They also advocate obtaining multiple image views and planes to increase the likelihood of successful imaging.¹⁷ 

The applications of the unified articular theory also extend beyond intraneural ganglia of the CPN. While the CPN is the most common location for intraneural ganglion occurrence,^6,17,20 cases have also been described of intraneural ganglion cysts of the tibial nerve at the proximal tibiofibular joint, as well as via the posterior tibial and medial plantar nerves at the subtalar joint within the tarsal tunnel.^11,18-23 Most cases involving the posterior tibial and medial plantar nerves were found in patients presenting with signs of tarsal tunnel syndrome.^22,23 Intraneural ganglia have also been found within the superficial peroneal nerve arising from the inferior tibiofibular joint.²⁰ In certain cases, these ganglia have also been noted to connect to the joint via a small articular branch.^19,22 In 1 case of an intraneural ganglion of the tibial nerve at the superior tibiofibular joint, initial conservative surgery led to early recurrence of symptoms.¹⁹ Just as in our case, the patient returned to the operating room and, after isolation and ligation of an articular branch, the patient experienced long-term resolution of both the symptoms and the cyst.¹⁹

Given the overwhelming evidence in support of the unified articular theory, we agree with the recommendation by Spinner and colleagues¹⁹ to search for an articular branch both via preoperative imaging and during the operation itself in all cases of intraneural ganglia. Assuming the mechanism of cyst formation is the same in most cases of intraneural ganglia, one could reasonably apply the same surgical techniques used in our case to the management of all intraneural ganglia, drastically reducing recurrence rates.

Conclusion

Based on research and corroborated by this case, the key to successful operative treatment of a common peroneal intraneural ganglion is division of the recurrent articular branch, which connects the proximal tibiofibular joint to the CPN.^6,9,11,12,14 Evidence has shown that disconnecting the articular branch and disrupting the source of the intraneural ganglion can resolve the condition and dramatically diminish the chance of recurrence.^6,8,12,14 This has become known as the unified articular theory.^6,12,14 Reports also suggest that, without disconnecting this articular branch, intraneural ganglion recurrence rates may be higher than 30%.^6,12,14,19 This case, therefore, supports the findings of previous authors^9-11,14 and provides an example of successful utilization of the treatment protocol delineated by Spinner and colleagues.^10,11

Intraneural ganglion cysts of peripheral nerves occurring within the epineural sheath are rare.^1-7 Case reports exist primarily within the neurosurgical literature, but very little in the orthopedic literature describes this condition. The peripheral nerve most commonly affected by an intraneural ganglion is the common peroneal nerve (CPN).^2,8,9 Such ganglia most often afflict middle-aged men with a history of micro- or macro-trauma and present with typical clinical manifestations of calf pain and progressive symptoms of ipsilateral foot drop and lower leg paresthesia.^2-5,10-12 The mechanism by which these ganglia form is not well understood and, as a result, treatment options are debated.⁶ Recent development of a “unified articular theory,” suggests that such intraneural ganglia of the CPN are fed by a small, recurrent articular branch of the CPN.^6,12,13 Cadaveric studies indicate that this branch originates from the deep peroneal nerve, just millimeters distal to the bifurcation of the CPN, and extends to the superior tibiofibular joint, providing direct access for cyst fluid to enter the CPN following the path of least resistance.^7,8,12,14 Therefore, according to the unified articular theory, the recommended treatment involves division of the articular branch, allowing the ganglion to be decompressed.⁶

We present a case of a 41-year-old man with an intraneural ganglion cyst of the CPN who was successfully treated, according to the recommendations of the unified articular theory. It is important for orthopedic surgeons to read about and recognize this condition, because knowledge of the operative technique outlined in our report allows it to be treated quite effectively. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 41-year-old man presented with a 2-month history of traumatic left lateral knee pain with numbness and weakness to the left foot and ankle. Initial examination showed a mild restriction of lumbosacral range of motion, with no complaints of lower back pain. Sciatic root stretch signs were negative. Strength testing of the lower extremities revealed 3+/5 strength of ankle dorsiflexion and great toe extension on the left side. There was a mild alteration in sensation to light touch on the lateral side of the left foot. Tenderness, without swelling, was present around the left fibular head. There was a positive Tinel sign over the peroneal nerve at the level of the fibular neck.

The patient was initially treated with anti-inflammatories and activity modification. An electromyogram (EMG)/nerve conduction study of the lower extremity showed a left peroneal nerve neurapraxia at the level of the fibular head. Noncontrast magnetic resonance imaging (MRI) of the left knee showed a “slightly prominent vein coursing posterior to the fibular head near the expected location of the common peroneal nerve,” according to the radiologist’s notes (Figure 1). The patient exhibited improvement with use of anti-inflammatories over several months. There was an increase in his ankle dorsiflexion strength to 4/5 and improvement in his pain and numbness.

Approximately 7 months after his initial presentation, the patient developed a marked worsening—increased numbness and weakness to ankle dorsiflexion—of his original symptoms. A repeat EMG/nerve conduction study of the lower extremity showed a persistent peroneal nerve neuropathy with a persistent denervation of the extensor hallucis longus, tibialis anterior, and extensor digitorum brevis muscles.

Because of continuing symptoms and increasing pain, the patient had surgery 8 months after his initial presentation. At that time, a markedly thickened peroneal nerve was identified. An incision in the epineural sheath released a clear gelatinous fluid consistent with a ganglion cyst. Through the epineural incision, the nerve was decompressed by manually “milking” the fluid from within the sheath. Approximately  30 mL of mucinous fluid was obtained and sent to pathology. No cells were identified.

Postoperatively, the patient noted a marked improvement in his pain. By 2 weeks postoperatively, the numbness in his foot had resolved. At 6 weeks after surgery, the strength of his tibialis anterior and extensor hallucis longus muscles had improved from 3+ to 4-, and he was free of pain.

At 2 months postoperatively, the patient redeveloped pain and numbness, and noted progressive weakness of his left foot and ankle. A repeat MRI of the left knee showed a dilated tubular structure corresponding to the course of the CPN. Comparison of this MRI with the initial MRI showed that the “prominent vein” was actually the dilated CPN.

He was taken to the operating room again 5 months after his first operation. At this time, the CPN was again noted to be markedly dilated (Figure 2). The nerve was explored and a recurrent branch to the proximal tibiofibular joint was identified and divided (Figures 3, 4). Through the divided branch, the CPN could be decompressed by manually “milking” the nerve in a proximal-to-distal direction, expressing clear gelatinous fluid consistent with a ganglion cyst (Figure 5). Pathology of the excised portion of the recurrent nerve was consistent with an intraneural ganglion cyst.

By 2 weeks postoperatively, the numbness of the patient’s left foot had completely resolved, as did his pain. By 3 months after surgery, his extensor hallucis longus strength was 5/5, and ankle dorsiflexion was 4-/5. At 6 months, his ankle dorsiflexion strength was 5/5, and he was completely asymptomatic. At 2 years postoperatively, he remained completely asymptomatic. A follow-up MRI of the left knee showed a ganglion cyst present at the proximal tibiofibular joint with resolution of the intraneural ganglion cyst within the CPN (Figure 6).

Discussion

Intraneural ganglia of peripheral nerves are relatively rare, most commonly occurring in the CPN.^6,8,9 A literature search reveals that this condition is only sparsely reported in orthopedic journals. This report, therefore, describes this rare, yet curable, condition. As noted, without appropriate intervention, the condition has a high likelihood of recurrence with only a brief interruption of symptoms.^6,8,9,12

The operative technique delineated in this report relies heavily on research demonstrating that peroneal intraneural ganglia develop from the superior tibiofibular joint and gain access to the CPN via the recurrent articular branch.^8,13 Research indicates that such ganglia preferentially proceed proximally along the deep portion of the CPN, within the epineurium.⁶ This hypothesis was corroborated in our case by the swollen appearance of the CPN proximal to its bifurcation.

Currently, there is no consensus on treatment of intraneural ganglion cysts of the CPN. However, evidence suggests that disconnection of the recurrent branch of the CPN may be important in successfully treating the condition.^6,9,14 This unified articular theory was initially proposed by Spinner and colleagues¹² in 2003 and recommends that surgical treatment focus on the articular branch as the source of cyst fluid.^6,9,12,14 This theory by Spinner and coauthors^12,14 was substantiated in our case: Once the articular branch was disconnected, cyst fluid was easily expressed via antegrade massage through the disconnected end. Pathologic analysis of a portion of the detached articular branch is also recommended to rule out other cystic lesions, such as cystic shwannomas.¹⁴

The history of the unified articular theory began in the mid-1990s, when Dr. Robert Spinner, board certified in both orthopedic and neurologic surgery, began researching causes of intraneural ganglion cysts. At the time, such ganglia were often treated by radical resection of the nerve and the cyst. Based on his review of literature, and his own cases, Spinner¹⁵ developed the theory that, just as with extraneural ganglia, these cysts are fed by fluid from the joint. According to Spinner,⁹ the sources of such connections were very small articular nerve branches that connect the nerve to the joint. His research led him to the original citation of such an intraneural ganglion of the ulnar nerve, first described by Dr. M. Beauchene, a French physician, in 1810.¹⁶ Spinner also discovered that Beauchene’s original dissection specimen had been preserved and was displayed in a medical museum in Paris. When Spinner went to France to view the specimen, he indeed found an intraneural ganglion of the ulnar nerve. On closer inspection, Spinner also discovered a small articular nerve branch containing a “hollow lumen” that would have been capable of allowing the passage of fluid into the nerve and leading to the development of a cyst.¹⁶

In our case, in the first operation, a simple incisional decompression of the CPN was performed. Unfortunately, the ganglion cyst quickly recurred, as did the patient’s symptoms. In the second surgical procedure, the articular branch connecting the peroneal nerve to the proximal tibiofibular joint was incised and disconnected from the nerve. This allowed the nerve to be decompressed and prevented a recurrence of the ganglion cyst within the nerve with complete resolution of the patient’s symptoms. This difference alone most likely accounts for the rapid recurrence of symptoms after the initial operation, since the fluid was simply drained, but the source was not detached, allowing the ganglion to recur.^6,12,14 This is similar in theory to excising the attachment of a ganglion cyst at the wrist from the underlying joint capsule rather than performing a needle aspiration or puncturing of the cyst.¹²

Regarding the imaging techniques used to identify intraneural ganglia, it is essential that the surgeon be aware of the unified articular theory and the likely presence of an articular branch. Such branches are extremely small and may be easily missed on imaging and intraoperatively.^17,18 MRI is the best method to image these cysts because of its superior ability to visualize soft-tissue lesions.^18,19 Intraneural ganglion cysts typically appear as homogenous, lobulated, well-circumscribed masses that are hyperintense on T2-weighted MRI.^3,19 Gadolinium may also offer diagnostic utility, because these masses do not enhance with its use on T1-weighted MRI.^3,17,19 By employing these techniques, one may easily view most of the ganglion cyst. To image the small articular branch, Spinner and colleagues¹⁷ recommend thin-section images with high–spatial resolution T2-imaging. They also advocate obtaining multiple image views and planes to increase the likelihood of successful imaging.¹⁷ 

The applications of the unified articular theory also extend beyond intraneural ganglia of the CPN. While the CPN is the most common location for intraneural ganglion occurrence,^6,17,20 cases have also been described of intraneural ganglion cysts of the tibial nerve at the proximal tibiofibular joint, as well as via the posterior tibial and medial plantar nerves at the subtalar joint within the tarsal tunnel.^11,18-23 Most cases involving the posterior tibial and medial plantar nerves were found in patients presenting with signs of tarsal tunnel syndrome.^22,23 Intraneural ganglia have also been found within the superficial peroneal nerve arising from the inferior tibiofibular joint.²⁰ In certain cases, these ganglia have also been noted to connect to the joint via a small articular branch.^19,22 In 1 case of an intraneural ganglion of the tibial nerve at the superior tibiofibular joint, initial conservative surgery led to early recurrence of symptoms.¹⁹ Just as in our case, the patient returned to the operating room and, after isolation and ligation of an articular branch, the patient experienced long-term resolution of both the symptoms and the cyst.¹⁹

Given the overwhelming evidence in support of the unified articular theory, we agree with the recommendation by Spinner and colleagues¹⁹ to search for an articular branch both via preoperative imaging and during the operation itself in all cases of intraneural ganglia. Assuming the mechanism of cyst formation is the same in most cases of intraneural ganglia, one could reasonably apply the same surgical techniques used in our case to the management of all intraneural ganglia, drastically reducing recurrence rates.

Conclusion

Based on research and corroborated by this case, the key to successful operative treatment of a common peroneal intraneural ganglion is division of the recurrent articular branch, which connects the proximal tibiofibular joint to the CPN.^6,9,11,12,14 Evidence has shown that disconnecting the articular branch and disrupting the source of the intraneural ganglion can resolve the condition and dramatically diminish the chance of recurrence.^6,8,12,14 This has become known as the unified articular theory.^6,12,14 Reports also suggest that, without disconnecting this articular branch, intraneural ganglion recurrence rates may be higher than 30%.^6,12,14,19 This case, therefore, supports the findings of previous authors^9-11,14 and provides an example of successful utilization of the treatment protocol delineated by Spinner and colleagues.^10,11

Osteoarthritis (OA) of the first carpometacarpal (CMC) joint is a common disabling condition that mostly affects women over 45 years of age.¹ Surgical intervention is usually indicated in advanced stage OA of the first CMC joint that has failed conservative treatment. Several surgical techniques have been described, including partial or total trapeziectomy, interposition arthroplasty with or without ligament reconstruction,^2,3 metacarpal osteotomy,⁴ hematoma and distraction arthroplasty,⁵ total joint arthroplasty, arthrodesis, and suspensionplasty.⁶ However, no single surgical procedure has proved to be superior.⁷

The Artelon implant (Artelon, Nashville, Tennessee) is a T-shaped spacer composed of a biocompatible and biodegradable polycaprolactone-based polyurethane urea polymer. The developers of the implant first presented its use in CMC OA in 2005.⁸ The device, an endoprosthetic replacement for the CMC joint, was designed to work through 2 modes of action: stabilization of the CMC joint by augmentation of the joint capsule and by formation of a new articular surface at the trapeziometacarpal interface. The interposed biomaterial has been described as preventing bony impingement and allowing time for replacement with a newly formed articular surface as it undergoes slow and controlled degradation.⁸

We present a patient with recurrent CMC pain and disability 4 years after arthroscopic hemitrapeziectomy and Artelon interposition and discuss the associated histologic findings. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 53-year-old man presented with painful disability of right thumb of several months’ duration. Clinical and radiographic evaluation supported the diagnosis of right thumb CMC joint Eaton stage III arthritis (Figures 1A, 1B). Surgical intervention was indicated after a failed course of conservative treatment, including splinting, nonsteroidal anti-inflammatory medications, activity modification, and corticosteroid injection. Preoperatively, the patient reported a visual analog scale (VAS) score of 8 with activity and 5 at rest, and a Disabilities of the Arm, Shoulder, and Hand (DASH) score of 72.5.

Arthroscopic débridement, hemitrapeziectomy, and interposition arthroplasty with the Artelon spacer were performed. Using standard thumb arthroscopy, 3 mm of the distal trapezium was excised and shaped parallel to scaphotrapezial joint. The wings of the standard-sized Artelon spacer were removed, and the central (articulating) portion was rolled into a tube and inserted through the 1R portal (directly radial to the abductor pollicis longus tendon) into the trapezial space. The Artelon spacer was unrolled within the joint to cover the remaining trapezium and was stabilized with the placement of a 0.045-inch Kirschner wire through the metacarpal, the spacer, and the remaining trapezium. The patient used a thumb spica splint for 4 weeks.

The postoperative radiographs showed a smooth and adequate hemitrapeziectomy with good alignment and implant position (Figures 2A, 2B). Four weeks after surgery, the Kirschner wire and cast were removed and physical therapy was initiated. The patient’s CMC pain gradually subsided. At the 3-month postoperative visit, the patient’s VAS score was 3 with activity and 1 at rest, with a DASH score of 28. His key pinch strength was 12 lb, compared with 20 lb on the contralateral side. At 6 months, the patient’s VAS score was 1 with activity and 0 at rest, with a DASH score of 12. His key pinch strength was 18 lb, compared with 22 lb on the contralateral side. At his 2-year postoperative visit, the patient was doing well with the exception of some mild residual pain when he opened tight jars. His VAS score was 1 with activity and 0 at rest, with a DASH score of 3. His key pinch strength was 20 lb, compared with 23 lb on the contralateral side. Radiographs showed good maintenance of the CMC space.

Four years postoperatively, the patient presented with worsening right CMC pain with decrease in pinch strength that interfered with his activities of daily living. His VAS score was 9 with activity and 6 at rest, with a DASH score of 70. On examination, pinch strength was 16 lb, compared with 22 lb on the contralateral side. Radiographs showed advancing arthritis with new osteophyte formation and irregular contour of distal trapezium (Figures 3A, 3B). The symptoms were refractory to conservative measures and continued to interfere with his activities of daily living. Revision surgical intervention was indicated and pursued in the form of an open CMC arthroplasty.

The intraoperative findings revealed degradation and disorganization of the Artelon implant within the central portion of the remaining distal trapezium. Rim osteophytes, especially along the ulnar aspect, were noted. Total trapeziectomy and débridement within the CMC space and suture-button suspensionplasty were performed.⁸ Slight degenerative changes of the distal scaphoid were also noted. The incision was irrigated, closed, and stabilized in a thumb spica splint (Figures 4A, 4B).

The harvested trapezium was immediately immersed in buffered formalin. The bone tissue was decalcified, dehydrated, embedded in paraffin, and sectioned in the coronal plane. The sections were stained with safranin O and trichrome, and light microscopic analysis was performed. Central erosion of distal trapezium without smooth resurfacing soft-tissue formation was noted grossly (Figure 5A) and microscopically (Figures 5B, 5C). The histologic morphology of the soft tissue over the distal trapezium was significantly different when compared with the smooth hyaline cartilage at the preserved trapezio-trapezoidal joint (Figures 6A-6F). Microscopic analysis also showed multinucleated giant cells within the soft tissue surrounding the degraded Artelon B (Figure 7).

Immunohistochemical analysis was performed to identify type I and type II collagen using the Histostain-Plus,3rd Gen IHC Detection Kit (Invitrogen Corporation, Camarillo, California) (Figures 8A-8F).⁹ The immunohistochemical stain was used to identify new hyaline cartilage formation that may have been induced by the Artelon as the resurfacing articulation. Hyaline cartilage contains mainly type II collagen, and collagen types VI, IX, X, XI, XII, and XIV all contribute to the mature matrix.¹⁰ Little type I collagen is found in hyaline cartilage. The results showed that the soft tissue over the distal trapezium with embedded Artelon fiber contained both type I and type II collagen. There was no visible hyaline cartilage formation induced by the Artelon. Both morphologic analysis and immunohistochemical staining revealed that the soft-tissue growth into the Artelon spacer on the distal trapezium consisted primarily of fibrocartilaginous tissue, which is composed mainly of type I collagen with some type II collagen.

Two weeks after total surgical excision of the Artelon implant, total trapeziectomy and suture-button suspensionplasty, the sutures were removed and physical therapy was initiated. Radiographs showed good alignment and position of thumb metacarpal with good maintenance of the implant and CMC space. Four months postoperatively, the patient reported that he was doing well without pain and without interference in his activities of daily living. On examination, the patient exhibited no pain with the CMC grind maneuver. Radial abduction of the right thumb was 85° and palmar abduction was 90° (compared with 100° and 90° of the left thumb), obtained by measuring the angle between thumb and index finger, respectively. Opposition was to the small finger metacarpophalangeal joint. Grip strength was 72 lb and pinch strength was 20 lb (compared with 70 lb and 24 lb, respectively, on the contralateral side). 

Discussion

The use of Artelon as an endoprosthetic spacer to treat osteoarthritis in the CMC joint of the thumb appears to stabilize and resurface the joint while avoiding total trapeziectomy.⁸ Nilsson and colleagues⁸ presented a prospective study concluding that the Artelon CMC spacer provided better pinch strength when compared with a traditional abductor pollicis longus suspensionplasty procedure. This study also suggested incorporation of the device in the surface of the adjacent bone with no signs of foreign-body reaction. The synthetic material was shown to be safe and biocompatible in vitro and in animal studies.^11-13

This case report describes the gross and histologic findings after continued pain led to explantation 4 years after arthroscopic partial trapeziectomy and insertion of the spacer. Intraoperative findings at this stage showed lack of incorporation of the Artelon material, central destruction of distal trapezium, and no evidence of smooth articular surface formation. Our histologic analysis showed only poorly organized fibrocartilage within the CMC space rather than a smooth articular surface. These histologic findings may correlate more with Jörheim and colleagues’¹⁴ matched cohort study, which showed that short-term outcomes after treatment with the Artelon implant were not clinically superior to those of tendon suspension-interposition arthroplasties. Multinucleated giant cells were also seen in our specimens. Choung and Tan¹⁵ presented a case report of foreign-body reaction to the Artelon spacer with histologic findings. The foreign body–type reactions associated with Artelon resulted in multinucleated giant cells in their specimens. Recently, several case reports have described similar foreign-body reactions.¹⁶ Nilsson and coauthors¹⁷ presented a randomized, controlled, multicenter study of 109 patients. They reported the Artelon CMC spacer did not result in superior results compared with tendon interposition arthroplasty. In a study by Gretzer and colleagues,¹⁸ the authors suggested that chronic inflammation may result from unstable Artelon fixation instead of the foreign-body reaction.

It is possible that the central erosion of the distal trapezium seen in our case may have resulted from chronic inflammation caused by foreign-body reaction and/or an unstably fixed spacer. The spacer was transfixed to the remaining trapezium in the CMC joint with a Kirschner wire followed by immobilization for 4 weeks. Poor soft-tissue integration of the Artelon spacer may have led to unintended motion and chronic inflammation, which may have also resulted in erosion between the Artelon spacer and the trapezium, leading to central destruction of the distal trapezium. Lastly, the byproducts formed by the degradation of the spacer may have resulted in erosion of the remaining trapezium.

Conclusion

The Artelon CMC spacer used in this patient provided comparable, but not superior, clinical results to other procedures. Histologically, the new articular surface in our patient was formed with rugged fibrocartilage instead of the expected smooth cartilaginous surface. The chronic inflammatory reaction may have resulted from foreign-body reaction, unstable implant fixation, or poor soft-tissue integration. This inflammatory reaction may have contributed to the patient’s recurrence of symptoms. These findings support recent clinical data that suggest the use of the Artelon spacer may not provide superior results to other surgical options for the treatment of CMC joint arthritis.

Osteoarthritis (OA) of the first carpometacarpal (CMC) joint is a common disabling condition that mostly affects women over 45 years of age.¹ Surgical intervention is usually indicated in advanced stage OA of the first CMC joint that has failed conservative treatment. Several surgical techniques have been described, including partial or total trapeziectomy, interposition arthroplasty with or without ligament reconstruction,^2,3 metacarpal osteotomy,⁴ hematoma and distraction arthroplasty,⁵ total joint arthroplasty, arthrodesis, and suspensionplasty.⁶ However, no single surgical procedure has proved to be superior.⁷

The Artelon implant (Artelon, Nashville, Tennessee) is a T-shaped spacer composed of a biocompatible and biodegradable polycaprolactone-based polyurethane urea polymer. The developers of the implant first presented its use in CMC OA in 2005.⁸ The device, an endoprosthetic replacement for the CMC joint, was designed to work through 2 modes of action: stabilization of the CMC joint by augmentation of the joint capsule and by formation of a new articular surface at the trapeziometacarpal interface. The interposed biomaterial has been described as preventing bony impingement and allowing time for replacement with a newly formed articular surface as it undergoes slow and controlled degradation.⁸

We present a patient with recurrent CMC pain and disability 4 years after arthroscopic hemitrapeziectomy and Artelon interposition and discuss the associated histologic findings. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 53-year-old man presented with painful disability of right thumb of several months’ duration. Clinical and radiographic evaluation supported the diagnosis of right thumb CMC joint Eaton stage III arthritis (Figures 1A, 1B). Surgical intervention was indicated after a failed course of conservative treatment, including splinting, nonsteroidal anti-inflammatory medications, activity modification, and corticosteroid injection. Preoperatively, the patient reported a visual analog scale (VAS) score of 8 with activity and 5 at rest, and a Disabilities of the Arm, Shoulder, and Hand (DASH) score of 72.5.

Arthroscopic débridement, hemitrapeziectomy, and interposition arthroplasty with the Artelon spacer were performed. Using standard thumb arthroscopy, 3 mm of the distal trapezium was excised and shaped parallel to scaphotrapezial joint. The wings of the standard-sized Artelon spacer were removed, and the central (articulating) portion was rolled into a tube and inserted through the 1R portal (directly radial to the abductor pollicis longus tendon) into the trapezial space. The Artelon spacer was unrolled within the joint to cover the remaining trapezium and was stabilized with the placement of a 0.045-inch Kirschner wire through the metacarpal, the spacer, and the remaining trapezium. The patient used a thumb spica splint for 4 weeks.

The postoperative radiographs showed a smooth and adequate hemitrapeziectomy with good alignment and implant position (Figures 2A, 2B). Four weeks after surgery, the Kirschner wire and cast were removed and physical therapy was initiated. The patient’s CMC pain gradually subsided. At the 3-month postoperative visit, the patient’s VAS score was 3 with activity and 1 at rest, with a DASH score of 28. His key pinch strength was 12 lb, compared with 20 lb on the contralateral side. At 6 months, the patient’s VAS score was 1 with activity and 0 at rest, with a DASH score of 12. His key pinch strength was 18 lb, compared with 22 lb on the contralateral side. At his 2-year postoperative visit, the patient was doing well with the exception of some mild residual pain when he opened tight jars. His VAS score was 1 with activity and 0 at rest, with a DASH score of 3. His key pinch strength was 20 lb, compared with 23 lb on the contralateral side. Radiographs showed good maintenance of the CMC space.

Four years postoperatively, the patient presented with worsening right CMC pain with decrease in pinch strength that interfered with his activities of daily living. His VAS score was 9 with activity and 6 at rest, with a DASH score of 70. On examination, pinch strength was 16 lb, compared with 22 lb on the contralateral side. Radiographs showed advancing arthritis with new osteophyte formation and irregular contour of distal trapezium (Figures 3A, 3B). The symptoms were refractory to conservative measures and continued to interfere with his activities of daily living. Revision surgical intervention was indicated and pursued in the form of an open CMC arthroplasty.

The intraoperative findings revealed degradation and disorganization of the Artelon implant within the central portion of the remaining distal trapezium. Rim osteophytes, especially along the ulnar aspect, were noted. Total trapeziectomy and débridement within the CMC space and suture-button suspensionplasty were performed.⁸ Slight degenerative changes of the distal scaphoid were also noted. The incision was irrigated, closed, and stabilized in a thumb spica splint (Figures 4A, 4B).

The harvested trapezium was immediately immersed in buffered formalin. The bone tissue was decalcified, dehydrated, embedded in paraffin, and sectioned in the coronal plane. The sections were stained with safranin O and trichrome, and light microscopic analysis was performed. Central erosion of distal trapezium without smooth resurfacing soft-tissue formation was noted grossly (Figure 5A) and microscopically (Figures 5B, 5C). The histologic morphology of the soft tissue over the distal trapezium was significantly different when compared with the smooth hyaline cartilage at the preserved trapezio-trapezoidal joint (Figures 6A-6F). Microscopic analysis also showed multinucleated giant cells within the soft tissue surrounding the degraded Artelon B (Figure 7).

Immunohistochemical analysis was performed to identify type I and type II collagen using the Histostain-Plus,3rd Gen IHC Detection Kit (Invitrogen Corporation, Camarillo, California) (Figures 8A-8F).⁹ The immunohistochemical stain was used to identify new hyaline cartilage formation that may have been induced by the Artelon as the resurfacing articulation. Hyaline cartilage contains mainly type II collagen, and collagen types VI, IX, X, XI, XII, and XIV all contribute to the mature matrix.¹⁰ Little type I collagen is found in hyaline cartilage. The results showed that the soft tissue over the distal trapezium with embedded Artelon fiber contained both type I and type II collagen. There was no visible hyaline cartilage formation induced by the Artelon. Both morphologic analysis and immunohistochemical staining revealed that the soft-tissue growth into the Artelon spacer on the distal trapezium consisted primarily of fibrocartilaginous tissue, which is composed mainly of type I collagen with some type II collagen.

Two weeks after total surgical excision of the Artelon implant, total trapeziectomy and suture-button suspensionplasty, the sutures were removed and physical therapy was initiated. Radiographs showed good alignment and position of thumb metacarpal with good maintenance of the implant and CMC space. Four months postoperatively, the patient reported that he was doing well without pain and without interference in his activities of daily living. On examination, the patient exhibited no pain with the CMC grind maneuver. Radial abduction of the right thumb was 85° and palmar abduction was 90° (compared with 100° and 90° of the left thumb), obtained by measuring the angle between thumb and index finger, respectively. Opposition was to the small finger metacarpophalangeal joint. Grip strength was 72 lb and pinch strength was 20 lb (compared with 70 lb and 24 lb, respectively, on the contralateral side). 

Discussion

The use of Artelon as an endoprosthetic spacer to treat osteoarthritis in the CMC joint of the thumb appears to stabilize and resurface the joint while avoiding total trapeziectomy.⁸ Nilsson and colleagues⁸ presented a prospective study concluding that the Artelon CMC spacer provided better pinch strength when compared with a traditional abductor pollicis longus suspensionplasty procedure. This study also suggested incorporation of the device in the surface of the adjacent bone with no signs of foreign-body reaction. The synthetic material was shown to be safe and biocompatible in vitro and in animal studies.^11-13

This case report describes the gross and histologic findings after continued pain led to explantation 4 years after arthroscopic partial trapeziectomy and insertion of the spacer. Intraoperative findings at this stage showed lack of incorporation of the Artelon material, central destruction of distal trapezium, and no evidence of smooth articular surface formation. Our histologic analysis showed only poorly organized fibrocartilage within the CMC space rather than a smooth articular surface. These histologic findings may correlate more with Jörheim and colleagues’¹⁴ matched cohort study, which showed that short-term outcomes after treatment with the Artelon implant were not clinically superior to those of tendon suspension-interposition arthroplasties. Multinucleated giant cells were also seen in our specimens. Choung and Tan¹⁵ presented a case report of foreign-body reaction to the Artelon spacer with histologic findings. The foreign body–type reactions associated with Artelon resulted in multinucleated giant cells in their specimens. Recently, several case reports have described similar foreign-body reactions.¹⁶ Nilsson and coauthors¹⁷ presented a randomized, controlled, multicenter study of 109 patients. They reported the Artelon CMC spacer did not result in superior results compared with tendon interposition arthroplasty. In a study by Gretzer and colleagues,¹⁸ the authors suggested that chronic inflammation may result from unstable Artelon fixation instead of the foreign-body reaction.

It is possible that the central erosion of the distal trapezium seen in our case may have resulted from chronic inflammation caused by foreign-body reaction and/or an unstably fixed spacer. The spacer was transfixed to the remaining trapezium in the CMC joint with a Kirschner wire followed by immobilization for 4 weeks. Poor soft-tissue integration of the Artelon spacer may have led to unintended motion and chronic inflammation, which may have also resulted in erosion between the Artelon spacer and the trapezium, leading to central destruction of the distal trapezium. Lastly, the byproducts formed by the degradation of the spacer may have resulted in erosion of the remaining trapezium.

Conclusion

The Artelon CMC spacer used in this patient provided comparable, but not superior, clinical results to other procedures. Histologically, the new articular surface in our patient was formed with rugged fibrocartilage instead of the expected smooth cartilaginous surface. The chronic inflammatory reaction may have resulted from foreign-body reaction, unstable implant fixation, or poor soft-tissue integration. This inflammatory reaction may have contributed to the patient’s recurrence of symptoms. These findings support recent clinical data that suggest the use of the Artelon spacer may not provide superior results to other surgical options for the treatment of CMC joint arthritis.

Osteoarthritis (OA) of the first carpometacarpal (CMC) joint is a common disabling condition that mostly affects women over 45 years of age.¹ Surgical intervention is usually indicated in advanced stage OA of the first CMC joint that has failed conservative treatment. Several surgical techniques have been described, including partial or total trapeziectomy, interposition arthroplasty with or without ligament reconstruction,^2,3 metacarpal osteotomy,⁴ hematoma and distraction arthroplasty,⁵ total joint arthroplasty, arthrodesis, and suspensionplasty.⁶ However, no single surgical procedure has proved to be superior.⁷

The Artelon implant (Artelon, Nashville, Tennessee) is a T-shaped spacer composed of a biocompatible and biodegradable polycaprolactone-based polyurethane urea polymer. The developers of the implant first presented its use in CMC OA in 2005.⁸ The device, an endoprosthetic replacement for the CMC joint, was designed to work through 2 modes of action: stabilization of the CMC joint by augmentation of the joint capsule and by formation of a new articular surface at the trapeziometacarpal interface. The interposed biomaterial has been described as preventing bony impingement and allowing time for replacement with a newly formed articular surface as it undergoes slow and controlled degradation.⁸

We present a patient with recurrent CMC pain and disability 4 years after arthroscopic hemitrapeziectomy and Artelon interposition and discuss the associated histologic findings. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 53-year-old man presented with painful disability of right thumb of several months’ duration. Clinical and radiographic evaluation supported the diagnosis of right thumb CMC joint Eaton stage III arthritis (Figures 1A, 1B). Surgical intervention was indicated after a failed course of conservative treatment, including splinting, nonsteroidal anti-inflammatory medications, activity modification, and corticosteroid injection. Preoperatively, the patient reported a visual analog scale (VAS) score of 8 with activity and 5 at rest, and a Disabilities of the Arm, Shoulder, and Hand (DASH) score of 72.5.

Arthroscopic débridement, hemitrapeziectomy, and interposition arthroplasty with the Artelon spacer were performed. Using standard thumb arthroscopy, 3 mm of the distal trapezium was excised and shaped parallel to scaphotrapezial joint. The wings of the standard-sized Artelon spacer were removed, and the central (articulating) portion was rolled into a tube and inserted through the 1R portal (directly radial to the abductor pollicis longus tendon) into the trapezial space. The Artelon spacer was unrolled within the joint to cover the remaining trapezium and was stabilized with the placement of a 0.045-inch Kirschner wire through the metacarpal, the spacer, and the remaining trapezium. The patient used a thumb spica splint for 4 weeks.

The postoperative radiographs showed a smooth and adequate hemitrapeziectomy with good alignment and implant position (Figures 2A, 2B). Four weeks after surgery, the Kirschner wire and cast were removed and physical therapy was initiated. The patient’s CMC pain gradually subsided. At the 3-month postoperative visit, the patient’s VAS score was 3 with activity and 1 at rest, with a DASH score of 28. His key pinch strength was 12 lb, compared with 20 lb on the contralateral side. At 6 months, the patient’s VAS score was 1 with activity and 0 at rest, with a DASH score of 12. His key pinch strength was 18 lb, compared with 22 lb on the contralateral side. At his 2-year postoperative visit, the patient was doing well with the exception of some mild residual pain when he opened tight jars. His VAS score was 1 with activity and 0 at rest, with a DASH score of 3. His key pinch strength was 20 lb, compared with 23 lb on the contralateral side. Radiographs showed good maintenance of the CMC space.

Four years postoperatively, the patient presented with worsening right CMC pain with decrease in pinch strength that interfered with his activities of daily living. His VAS score was 9 with activity and 6 at rest, with a DASH score of 70. On examination, pinch strength was 16 lb, compared with 22 lb on the contralateral side. Radiographs showed advancing arthritis with new osteophyte formation and irregular contour of distal trapezium (Figures 3A, 3B). The symptoms were refractory to conservative measures and continued to interfere with his activities of daily living. Revision surgical intervention was indicated and pursued in the form of an open CMC arthroplasty.

The intraoperative findings revealed degradation and disorganization of the Artelon implant within the central portion of the remaining distal trapezium. Rim osteophytes, especially along the ulnar aspect, were noted. Total trapeziectomy and débridement within the CMC space and suture-button suspensionplasty were performed.⁸ Slight degenerative changes of the distal scaphoid were also noted. The incision was irrigated, closed, and stabilized in a thumb spica splint (Figures 4A, 4B).

The harvested trapezium was immediately immersed in buffered formalin. The bone tissue was decalcified, dehydrated, embedded in paraffin, and sectioned in the coronal plane. The sections were stained with safranin O and trichrome, and light microscopic analysis was performed. Central erosion of distal trapezium without smooth resurfacing soft-tissue formation was noted grossly (Figure 5A) and microscopically (Figures 5B, 5C). The histologic morphology of the soft tissue over the distal trapezium was significantly different when compared with the smooth hyaline cartilage at the preserved trapezio-trapezoidal joint (Figures 6A-6F). Microscopic analysis also showed multinucleated giant cells within the soft tissue surrounding the degraded Artelon B (Figure 7).

Immunohistochemical analysis was performed to identify type I and type II collagen using the Histostain-Plus,3rd Gen IHC Detection Kit (Invitrogen Corporation, Camarillo, California) (Figures 8A-8F).⁹ The immunohistochemical stain was used to identify new hyaline cartilage formation that may have been induced by the Artelon as the resurfacing articulation. Hyaline cartilage contains mainly type II collagen, and collagen types VI, IX, X, XI, XII, and XIV all contribute to the mature matrix.¹⁰ Little type I collagen is found in hyaline cartilage. The results showed that the soft tissue over the distal trapezium with embedded Artelon fiber contained both type I and type II collagen. There was no visible hyaline cartilage formation induced by the Artelon. Both morphologic analysis and immunohistochemical staining revealed that the soft-tissue growth into the Artelon spacer on the distal trapezium consisted primarily of fibrocartilaginous tissue, which is composed mainly of type I collagen with some type II collagen.

Two weeks after total surgical excision of the Artelon implant, total trapeziectomy and suture-button suspensionplasty, the sutures were removed and physical therapy was initiated. Radiographs showed good alignment and position of thumb metacarpal with good maintenance of the implant and CMC space. Four months postoperatively, the patient reported that he was doing well without pain and without interference in his activities of daily living. On examination, the patient exhibited no pain with the CMC grind maneuver. Radial abduction of the right thumb was 85° and palmar abduction was 90° (compared with 100° and 90° of the left thumb), obtained by measuring the angle between thumb and index finger, respectively. Opposition was to the small finger metacarpophalangeal joint. Grip strength was 72 lb and pinch strength was 20 lb (compared with 70 lb and 24 lb, respectively, on the contralateral side). 

Discussion

The use of Artelon as an endoprosthetic spacer to treat osteoarthritis in the CMC joint of the thumb appears to stabilize and resurface the joint while avoiding total trapeziectomy.⁸ Nilsson and colleagues⁸ presented a prospective study concluding that the Artelon CMC spacer provided better pinch strength when compared with a traditional abductor pollicis longus suspensionplasty procedure. This study also suggested incorporation of the device in the surface of the adjacent bone with no signs of foreign-body reaction. The synthetic material was shown to be safe and biocompatible in vitro and in animal studies.^11-13

This case report describes the gross and histologic findings after continued pain led to explantation 4 years after arthroscopic partial trapeziectomy and insertion of the spacer. Intraoperative findings at this stage showed lack of incorporation of the Artelon material, central destruction of distal trapezium, and no evidence of smooth articular surface formation. Our histologic analysis showed only poorly organized fibrocartilage within the CMC space rather than a smooth articular surface. These histologic findings may correlate more with Jörheim and colleagues’¹⁴ matched cohort study, which showed that short-term outcomes after treatment with the Artelon implant were not clinically superior to those of tendon suspension-interposition arthroplasties. Multinucleated giant cells were also seen in our specimens. Choung and Tan¹⁵ presented a case report of foreign-body reaction to the Artelon spacer with histologic findings. The foreign body–type reactions associated with Artelon resulted in multinucleated giant cells in their specimens. Recently, several case reports have described similar foreign-body reactions.¹⁶ Nilsson and coauthors¹⁷ presented a randomized, controlled, multicenter study of 109 patients. They reported the Artelon CMC spacer did not result in superior results compared with tendon interposition arthroplasty. In a study by Gretzer and colleagues,¹⁸ the authors suggested that chronic inflammation may result from unstable Artelon fixation instead of the foreign-body reaction.

It is possible that the central erosion of the distal trapezium seen in our case may have resulted from chronic inflammation caused by foreign-body reaction and/or an unstably fixed spacer. The spacer was transfixed to the remaining trapezium in the CMC joint with a Kirschner wire followed by immobilization for 4 weeks. Poor soft-tissue integration of the Artelon spacer may have led to unintended motion and chronic inflammation, which may have also resulted in erosion between the Artelon spacer and the trapezium, leading to central destruction of the distal trapezium. Lastly, the byproducts formed by the degradation of the spacer may have resulted in erosion of the remaining trapezium.

Conclusion

The Artelon CMC spacer used in this patient provided comparable, but not superior, clinical results to other procedures. Histologically, the new articular surface in our patient was formed with rugged fibrocartilage instead of the expected smooth cartilaginous surface. The chronic inflammatory reaction may have resulted from foreign-body reaction, unstable implant fixation, or poor soft-tissue integration. This inflammatory reaction may have contributed to the patient’s recurrence of symptoms. These findings support recent clinical data that suggest the use of the Artelon spacer may not provide superior results to other surgical options for the treatment of CMC joint arthritis.

Symptomatic synovial cyst formation is a rare, late occurrence after total knee arthroplasty (TKA); these cysts are generally discovered by chance. If they enlarge, they can result in significant pain and disability. A few case reports have described the development of very large cysts that required revision knee surgery. In this patient, polyethylene wear disease after TKA resulted in a massive synovial cyst that extended into the posterior compartment of the leg, as well as a progressive peripheral neuropathy. Revision of a loose patella component and worn polyethylene liner with complete synovectomy, plus decompression of the cyst via needle aspiration, resulted in an excellent short-term outcome.

To the author’s knowledge, this is the first case report of peripheral neuropathy of the tibial nerve secondary to a massive Baker cyst after total knee replacement. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

The patient was a 65-year-old woman with a complex medical history and multiple left knee surgeries, including a high tibial osteotomy and subsequent cemented TKA performed in the mid-1990s. She presented to the orthopedic department at a university hospital with complaints of knee pain 13 years after TKA. Observation was recommended; however, she was lost to follow-up.

The patient presented to her primary care physician (PCP) 16 years after TKA with a very large, painful mass in the back of her left leg. An ultrasound showed a large Baker cyst, and the patient was sent to interventional radiology. A few months later, she had an ultrasound-guided aspiration into the left calf, which produced 300 mL of thick synovial fluid. A cell count was not performed, but bacterial cultures were negative. Immediately after the aspiration, the pain was relieved.

Approximately 3 months after the aspiration, she presented again to her PCP with re-accumulation of fluid in the back of her left leg and severe leg pain. She was referred to a different orthopedic surgeon who determined that the risk of surgery was too great given her complex medical history.

The woman’s PCP referred the woman to our office 6 months after the aspiration. On presentation, her pain was localized to the posterior left leg. She reported the pain level as a constant 9 out of 10 on the visual analog scale, despite ingesting high doses of narcotics, including oxycontin and morphine. Her physical examination was remarkable for an ill-defined large calf mass. The posterior compartment of her left leg was firm and severely tender, similar to the characteristic findings seen in acute compartment syndrome.

Radiographs showed evidence of asymmetric polyethylene wear on the medial side of the knee (Figures 1A, 1B). Serum labs were ordered to evaluate for infection. C-reactive protein was mildly elevated at 5.5 mg/L (normal range, 0-5 mg/L); however, the erythrocyte sedimentation rate was normal at 12 mm/h (normal range, 0-20 mm/h). Magnetic resonance imaging of the left lower extremity with intravenous contrast showed the presence of a very large Baker cyst contained within the posterior compartment of the knee and a smaller surrounding cyst adjacent to the popliteal neurovascular bundle (Figure 2).

The Baker cyst was re-aspirated in the office. The automated synovial fluid cell count could not be performed because of high fluid viscosity. However, a manual review of the fluid specimen under light microscopy revealed proteinaceous, viscous tan-colored fluid containing no neutrophils and a few macrophages. Fluid cytology was also sent for review under polarizing light microscopy as described by Peterson and colleagues.¹ Scattered fragments of polarizable foreign material were consistent with polyethylene debris (Figure 3). 

The patient was counseled about the risks and benefits of surgery and was offered revision TKA with polyethylene liner exchange and synovectomy, only after complete cessation of smoking. She underwent serum nicotine monitoring to ensure tobacco cessation; however, she also reported the onset of a progressive sensory deficit over her left foot during this period. Although her medical history was remarkable for spinal stenosis, she noted a progressive decline in sensory function and new-onset paresthesia of her left foot.

An urgent consult to neurology was requested for nerve conduction studies. According to the electrodiagnostic study, the patient had a moderately severe left tibial neuropathy, likely at the popliteal fossa or distal to it. The nerve conduction study showed a chronic tibial nerve peripheral compressive mononeuropathy, and she was immediately scheduled for revision knee surgery with decompression of her Baker cyst to prevent further neurologic deficit.

During surgery, the knee joint exhibited hypertrophic synovitis with a characteristic pale-yellowish discoloration secondary to significant polyethylene wear disease (Figure 4). The polyethylene liner was severely worn with pitting, cracking, and delamination (Figure 5). While the patellar component was grossly loose, the tibial and femoral components were stable. After a complete synovectomy, the loose patellar component and tibial polyethylene liner were replaced. Osteolytic areas within the tibia underwent curettage and allograft impaction grafting. Lastly, decompression of the ruptured Baker cyst was performed via a 16-gauge needle placed in the posterior compartment of the left leg. The calf was gently squeezed with a “milking” maneuver, which yielded approximately 200 mL of thick, mucoid yellowish-brown synovial fluid resembling tapioca pudding (Figure 6).

Postoperatively, all intraoperative cultures were negative, and the patient was followed closely at 1 week, 2 weeks, 6 weeks, and 3 months after the surgery. At her latest follow-up, the posterior leg compartment remained decompressed and her progressive sensory deficit had nearly resolved. Moreover, the left leg and posterior knee pain completely resolved.

Discussion

A leading cause of TKA failure is attributed to aseptic loosening from polyethylene wear disease.² Implanted high-molecular-weight polyethylene (HMWPE) liners are known to undergo a variety of mechanical wear patterns within the knee. Observed patterns include pitting, scratching, burnishing, scratching, and delamination, which can all liberate numerous fine polyethylene particles.³ This wear debris induces macrophage phagocytosis that triggers an inflammatory reaction within the knee joint and can lead to synovitis, repeat effusions and, ultimately, to aseptic loosening.

Prior to 1996, polyethylene used in total knee replacement underwent a sterilization process in air. This oxygen-rich environment led to the development of free radical formation within the HMWPE. Ultimately, this had a detrimental effect on the polyethylene, leading to the formation of increased wear debris.⁴

Subsequently, orthopedic companies have changed their sterilization and manufacturing methods. Polyethylene components now undergo a variety of processes to eliminate or reduce oxidation, free-radical formation, and mechanical wear debris. Now, sterilization typically takes place in an inert atmospheric environment. Modern HMWPE implants often undergo higher irradiation to induce mechanical cross-linking, followed by either a re-annealing or remelting step. In other cases, manufacturers “dope” their polyethylene with vitamin E to quench free radicals within the material. While these steps have reduced the number of in vitro wear particles, the problem of wear debris, subsequent osteolysis, and aseptic loosening has not been eliminated.^1-5 

Polyethylene wear debris within the synovial fluid or tissue of failed TKAs can be identified with scanning electron microscopy or by light microscopy utilizing polarized light.¹ In this particular case, wear debris was confirmed within the synovial tissue and in the fluid of the Baker cyst by microscopic analysis.

Formation of a popliteal or Baker cyst as a result of polyethylene wear disease is an infrequent but known complication of TKA. Reports have demonstrated variable success in cyst eradication when revision surgery is performed on knees with synovial cysts. Most of these reports indicate that cyst formation tends to occur as a late complication (7 or more years) after TKA.^6-12

Treatment options may include skillful observation with close follow-up or revision surgery. Polyethylene exchange with synovectomy when feasible, as well as component revision with or without excision of the synovial cyst, are surgical options.

Niki and colleagues¹³ described a gigantic popliteal synovial cyst caused by wear particles after TKA. In this report, the surgeon performed a synovectomy and polyethylene liner exchange with retention of prosthetic components. At 12-month follow-up, the patient was reported to be doing well.

Mavrogenis and coauthors¹⁴ reported a wear debris–induced pseudotumor in the popliteal fossa and calf after TKA. In this case, in addition to the synovectomy, the surgeon removed all prosthetic components and used a semi-constrained implant to revise the knee. At 30-month follow-up, the patient reported having a painless knee.

While case reports have indicated that revision TKA for large, painful synovial cysts is a reasonable treatment option in carefully selected patients, there is a paucity of literature on this subject. Moreover, the present case appears to be the first literature report of a tibial nerve compressive neuropathy secondary to a synovial cyst after TKA.

Conclusion

In this report, polyethylene wear disease after TKA resulted in a massive synovial cyst extending into the posterior compartment of the leg. A progressive peripheral neuropathy confirmed by electromyography was also discovered. The patient underwent revision of a loose patellar component and worn polyethylene liner with complete synovectomy plus decompression of the cyst via needle aspiration. This resulted in an excellent short-term outcome with resolution of pain and significant improvement of the peripheral neuropathy 3 months after surgery.

Symptomatic synovial cyst formation is a rare, late occurrence after total knee arthroplasty (TKA); these cysts are generally discovered by chance. If they enlarge, they can result in significant pain and disability. A few case reports have described the development of very large cysts that required revision knee surgery. In this patient, polyethylene wear disease after TKA resulted in a massive synovial cyst that extended into the posterior compartment of the leg, as well as a progressive peripheral neuropathy. Revision of a loose patella component and worn polyethylene liner with complete synovectomy, plus decompression of the cyst via needle aspiration, resulted in an excellent short-term outcome.

To the author’s knowledge, this is the first case report of peripheral neuropathy of the tibial nerve secondary to a massive Baker cyst after total knee replacement. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

The patient was a 65-year-old woman with a complex medical history and multiple left knee surgeries, including a high tibial osteotomy and subsequent cemented TKA performed in the mid-1990s. She presented to the orthopedic department at a university hospital with complaints of knee pain 13 years after TKA. Observation was recommended; however, she was lost to follow-up.

The patient presented to her primary care physician (PCP) 16 years after TKA with a very large, painful mass in the back of her left leg. An ultrasound showed a large Baker cyst, and the patient was sent to interventional radiology. A few months later, she had an ultrasound-guided aspiration into the left calf, which produced 300 mL of thick synovial fluid. A cell count was not performed, but bacterial cultures were negative. Immediately after the aspiration, the pain was relieved.

Approximately 3 months after the aspiration, she presented again to her PCP with re-accumulation of fluid in the back of her left leg and severe leg pain. She was referred to a different orthopedic surgeon who determined that the risk of surgery was too great given her complex medical history.

The woman’s PCP referred the woman to our office 6 months after the aspiration. On presentation, her pain was localized to the posterior left leg. She reported the pain level as a constant 9 out of 10 on the visual analog scale, despite ingesting high doses of narcotics, including oxycontin and morphine. Her physical examination was remarkable for an ill-defined large calf mass. The posterior compartment of her left leg was firm and severely tender, similar to the characteristic findings seen in acute compartment syndrome.

Radiographs showed evidence of asymmetric polyethylene wear on the medial side of the knee (Figures 1A, 1B). Serum labs were ordered to evaluate for infection. C-reactive protein was mildly elevated at 5.5 mg/L (normal range, 0-5 mg/L); however, the erythrocyte sedimentation rate was normal at 12 mm/h (normal range, 0-20 mm/h). Magnetic resonance imaging of the left lower extremity with intravenous contrast showed the presence of a very large Baker cyst contained within the posterior compartment of the knee and a smaller surrounding cyst adjacent to the popliteal neurovascular bundle (Figure 2).

The Baker cyst was re-aspirated in the office. The automated synovial fluid cell count could not be performed because of high fluid viscosity. However, a manual review of the fluid specimen under light microscopy revealed proteinaceous, viscous tan-colored fluid containing no neutrophils and a few macrophages. Fluid cytology was also sent for review under polarizing light microscopy as described by Peterson and colleagues.¹ Scattered fragments of polarizable foreign material were consistent with polyethylene debris (Figure 3). 

The patient was counseled about the risks and benefits of surgery and was offered revision TKA with polyethylene liner exchange and synovectomy, only after complete cessation of smoking. She underwent serum nicotine monitoring to ensure tobacco cessation; however, she also reported the onset of a progressive sensory deficit over her left foot during this period. Although her medical history was remarkable for spinal stenosis, she noted a progressive decline in sensory function and new-onset paresthesia of her left foot.

An urgent consult to neurology was requested for nerve conduction studies. According to the electrodiagnostic study, the patient had a moderately severe left tibial neuropathy, likely at the popliteal fossa or distal to it. The nerve conduction study showed a chronic tibial nerve peripheral compressive mononeuropathy, and she was immediately scheduled for revision knee surgery with decompression of her Baker cyst to prevent further neurologic deficit.

During surgery, the knee joint exhibited hypertrophic synovitis with a characteristic pale-yellowish discoloration secondary to significant polyethylene wear disease (Figure 4). The polyethylene liner was severely worn with pitting, cracking, and delamination (Figure 5). While the patellar component was grossly loose, the tibial and femoral components were stable. After a complete synovectomy, the loose patellar component and tibial polyethylene liner were replaced. Osteolytic areas within the tibia underwent curettage and allograft impaction grafting. Lastly, decompression of the ruptured Baker cyst was performed via a 16-gauge needle placed in the posterior compartment of the left leg. The calf was gently squeezed with a “milking” maneuver, which yielded approximately 200 mL of thick, mucoid yellowish-brown synovial fluid resembling tapioca pudding (Figure 6).

Postoperatively, all intraoperative cultures were negative, and the patient was followed closely at 1 week, 2 weeks, 6 weeks, and 3 months after the surgery. At her latest follow-up, the posterior leg compartment remained decompressed and her progressive sensory deficit had nearly resolved. Moreover, the left leg and posterior knee pain completely resolved.

Discussion

A leading cause of TKA failure is attributed to aseptic loosening from polyethylene wear disease.² Implanted high-molecular-weight polyethylene (HMWPE) liners are known to undergo a variety of mechanical wear patterns within the knee. Observed patterns include pitting, scratching, burnishing, scratching, and delamination, which can all liberate numerous fine polyethylene particles.³ This wear debris induces macrophage phagocytosis that triggers an inflammatory reaction within the knee joint and can lead to synovitis, repeat effusions and, ultimately, to aseptic loosening.

Prior to 1996, polyethylene used in total knee replacement underwent a sterilization process in air. This oxygen-rich environment led to the development of free radical formation within the HMWPE. Ultimately, this had a detrimental effect on the polyethylene, leading to the formation of increased wear debris.⁴

Subsequently, orthopedic companies have changed their sterilization and manufacturing methods. Polyethylene components now undergo a variety of processes to eliminate or reduce oxidation, free-radical formation, and mechanical wear debris. Now, sterilization typically takes place in an inert atmospheric environment. Modern HMWPE implants often undergo higher irradiation to induce mechanical cross-linking, followed by either a re-annealing or remelting step. In other cases, manufacturers “dope” their polyethylene with vitamin E to quench free radicals within the material. While these steps have reduced the number of in vitro wear particles, the problem of wear debris, subsequent osteolysis, and aseptic loosening has not been eliminated.^1-5 

Polyethylene wear debris within the synovial fluid or tissue of failed TKAs can be identified with scanning electron microscopy or by light microscopy utilizing polarized light.¹ In this particular case, wear debris was confirmed within the synovial tissue and in the fluid of the Baker cyst by microscopic analysis.

Formation of a popliteal or Baker cyst as a result of polyethylene wear disease is an infrequent but known complication of TKA. Reports have demonstrated variable success in cyst eradication when revision surgery is performed on knees with synovial cysts. Most of these reports indicate that cyst formation tends to occur as a late complication (7 or more years) after TKA.^6-12

Treatment options may include skillful observation with close follow-up or revision surgery. Polyethylene exchange with synovectomy when feasible, as well as component revision with or without excision of the synovial cyst, are surgical options.

Niki and colleagues¹³ described a gigantic popliteal synovial cyst caused by wear particles after TKA. In this report, the surgeon performed a synovectomy and polyethylene liner exchange with retention of prosthetic components. At 12-month follow-up, the patient was reported to be doing well.

Mavrogenis and coauthors¹⁴ reported a wear debris–induced pseudotumor in the popliteal fossa and calf after TKA. In this case, in addition to the synovectomy, the surgeon removed all prosthetic components and used a semi-constrained implant to revise the knee. At 30-month follow-up, the patient reported having a painless knee.

While case reports have indicated that revision TKA for large, painful synovial cysts is a reasonable treatment option in carefully selected patients, there is a paucity of literature on this subject. Moreover, the present case appears to be the first literature report of a tibial nerve compressive neuropathy secondary to a synovial cyst after TKA.

Conclusion

In this report, polyethylene wear disease after TKA resulted in a massive synovial cyst extending into the posterior compartment of the leg. A progressive peripheral neuropathy confirmed by electromyography was also discovered. The patient underwent revision of a loose patellar component and worn polyethylene liner with complete synovectomy plus decompression of the cyst via needle aspiration. This resulted in an excellent short-term outcome with resolution of pain and significant improvement of the peripheral neuropathy 3 months after surgery.

Symptomatic synovial cyst formation is a rare, late occurrence after total knee arthroplasty (TKA); these cysts are generally discovered by chance. If they enlarge, they can result in significant pain and disability. A few case reports have described the development of very large cysts that required revision knee surgery. In this patient, polyethylene wear disease after TKA resulted in a massive synovial cyst that extended into the posterior compartment of the leg, as well as a progressive peripheral neuropathy. Revision of a loose patella component and worn polyethylene liner with complete synovectomy, plus decompression of the cyst via needle aspiration, resulted in an excellent short-term outcome.

To the author’s knowledge, this is the first case report of peripheral neuropathy of the tibial nerve secondary to a massive Baker cyst after total knee replacement. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

The patient was a 65-year-old woman with a complex medical history and multiple left knee surgeries, including a high tibial osteotomy and subsequent cemented TKA performed in the mid-1990s. She presented to the orthopedic department at a university hospital with complaints of knee pain 13 years after TKA. Observation was recommended; however, she was lost to follow-up.

The patient presented to her primary care physician (PCP) 16 years after TKA with a very large, painful mass in the back of her left leg. An ultrasound showed a large Baker cyst, and the patient was sent to interventional radiology. A few months later, she had an ultrasound-guided aspiration into the left calf, which produced 300 mL of thick synovial fluid. A cell count was not performed, but bacterial cultures were negative. Immediately after the aspiration, the pain was relieved.

Approximately 3 months after the aspiration, she presented again to her PCP with re-accumulation of fluid in the back of her left leg and severe leg pain. She was referred to a different orthopedic surgeon who determined that the risk of surgery was too great given her complex medical history.

The woman’s PCP referred the woman to our office 6 months after the aspiration. On presentation, her pain was localized to the posterior left leg. She reported the pain level as a constant 9 out of 10 on the visual analog scale, despite ingesting high doses of narcotics, including oxycontin and morphine. Her physical examination was remarkable for an ill-defined large calf mass. The posterior compartment of her left leg was firm and severely tender, similar to the characteristic findings seen in acute compartment syndrome.

Radiographs showed evidence of asymmetric polyethylene wear on the medial side of the knee (Figures 1A, 1B). Serum labs were ordered to evaluate for infection. C-reactive protein was mildly elevated at 5.5 mg/L (normal range, 0-5 mg/L); however, the erythrocyte sedimentation rate was normal at 12 mm/h (normal range, 0-20 mm/h). Magnetic resonance imaging of the left lower extremity with intravenous contrast showed the presence of a very large Baker cyst contained within the posterior compartment of the knee and a smaller surrounding cyst adjacent to the popliteal neurovascular bundle (Figure 2).

The Baker cyst was re-aspirated in the office. The automated synovial fluid cell count could not be performed because of high fluid viscosity. However, a manual review of the fluid specimen under light microscopy revealed proteinaceous, viscous tan-colored fluid containing no neutrophils and a few macrophages. Fluid cytology was also sent for review under polarizing light microscopy as described by Peterson and colleagues.¹ Scattered fragments of polarizable foreign material were consistent with polyethylene debris (Figure 3). 

The patient was counseled about the risks and benefits of surgery and was offered revision TKA with polyethylene liner exchange and synovectomy, only after complete cessation of smoking. She underwent serum nicotine monitoring to ensure tobacco cessation; however, she also reported the onset of a progressive sensory deficit over her left foot during this period. Although her medical history was remarkable for spinal stenosis, she noted a progressive decline in sensory function and new-onset paresthesia of her left foot.

An urgent consult to neurology was requested for nerve conduction studies. According to the electrodiagnostic study, the patient had a moderately severe left tibial neuropathy, likely at the popliteal fossa or distal to it. The nerve conduction study showed a chronic tibial nerve peripheral compressive mononeuropathy, and she was immediately scheduled for revision knee surgery with decompression of her Baker cyst to prevent further neurologic deficit.

During surgery, the knee joint exhibited hypertrophic synovitis with a characteristic pale-yellowish discoloration secondary to significant polyethylene wear disease (Figure 4). The polyethylene liner was severely worn with pitting, cracking, and delamination (Figure 5). While the patellar component was grossly loose, the tibial and femoral components were stable. After a complete synovectomy, the loose patellar component and tibial polyethylene liner were replaced. Osteolytic areas within the tibia underwent curettage and allograft impaction grafting. Lastly, decompression of the ruptured Baker cyst was performed via a 16-gauge needle placed in the posterior compartment of the left leg. The calf was gently squeezed with a “milking” maneuver, which yielded approximately 200 mL of thick, mucoid yellowish-brown synovial fluid resembling tapioca pudding (Figure 6).

Postoperatively, all intraoperative cultures were negative, and the patient was followed closely at 1 week, 2 weeks, 6 weeks, and 3 months after the surgery. At her latest follow-up, the posterior leg compartment remained decompressed and her progressive sensory deficit had nearly resolved. Moreover, the left leg and posterior knee pain completely resolved.

Discussion

A leading cause of TKA failure is attributed to aseptic loosening from polyethylene wear disease.² Implanted high-molecular-weight polyethylene (HMWPE) liners are known to undergo a variety of mechanical wear patterns within the knee. Observed patterns include pitting, scratching, burnishing, scratching, and delamination, which can all liberate numerous fine polyethylene particles.³ This wear debris induces macrophage phagocytosis that triggers an inflammatory reaction within the knee joint and can lead to synovitis, repeat effusions and, ultimately, to aseptic loosening.

Prior to 1996, polyethylene used in total knee replacement underwent a sterilization process in air. This oxygen-rich environment led to the development of free radical formation within the HMWPE. Ultimately, this had a detrimental effect on the polyethylene, leading to the formation of increased wear debris.⁴

Subsequently, orthopedic companies have changed their sterilization and manufacturing methods. Polyethylene components now undergo a variety of processes to eliminate or reduce oxidation, free-radical formation, and mechanical wear debris. Now, sterilization typically takes place in an inert atmospheric environment. Modern HMWPE implants often undergo higher irradiation to induce mechanical cross-linking, followed by either a re-annealing or remelting step. In other cases, manufacturers “dope” their polyethylene with vitamin E to quench free radicals within the material. While these steps have reduced the number of in vitro wear particles, the problem of wear debris, subsequent osteolysis, and aseptic loosening has not been eliminated.^1-5 

Polyethylene wear debris within the synovial fluid or tissue of failed TKAs can be identified with scanning electron microscopy or by light microscopy utilizing polarized light.¹ In this particular case, wear debris was confirmed within the synovial tissue and in the fluid of the Baker cyst by microscopic analysis.

Formation of a popliteal or Baker cyst as a result of polyethylene wear disease is an infrequent but known complication of TKA. Reports have demonstrated variable success in cyst eradication when revision surgery is performed on knees with synovial cysts. Most of these reports indicate that cyst formation tends to occur as a late complication (7 or more years) after TKA.^6-12

Treatment options may include skillful observation with close follow-up or revision surgery. Polyethylene exchange with synovectomy when feasible, as well as component revision with or without excision of the synovial cyst, are surgical options.

Niki and colleagues¹³ described a gigantic popliteal synovial cyst caused by wear particles after TKA. In this report, the surgeon performed a synovectomy and polyethylene liner exchange with retention of prosthetic components. At 12-month follow-up, the patient was reported to be doing well.

Mavrogenis and coauthors¹⁴ reported a wear debris–induced pseudotumor in the popliteal fossa and calf after TKA. In this case, in addition to the synovectomy, the surgeon removed all prosthetic components and used a semi-constrained implant to revise the knee. At 30-month follow-up, the patient reported having a painless knee.

While case reports have indicated that revision TKA for large, painful synovial cysts is a reasonable treatment option in carefully selected patients, there is a paucity of literature on this subject. Moreover, the present case appears to be the first literature report of a tibial nerve compressive neuropathy secondary to a synovial cyst after TKA.

Conclusion

In this report, polyethylene wear disease after TKA resulted in a massive synovial cyst extending into the posterior compartment of the leg. A progressive peripheral neuropathy confirmed by electromyography was also discovered. The patient underwent revision of a loose patellar component and worn polyethylene liner with complete synovectomy plus decompression of the cyst via needle aspiration. This resulted in an excellent short-term outcome with resolution of pain and significant improvement of the peripheral neuropathy 3 months after surgery.

Anterior-inferior and posterior-inferior labral tears are common injuries treated with arthroscopic surgery¹ typically performed with beach-chair^2,3 or lateral decubitus^1,2 positioning and variable headrest positioning. Iatrogenic nerve damage that occurs after arthroscopic shoulder surgery—including damage to the suprascapular, axillary, musculocutaneous, subscapular, and spinal accessory nerves—has recently been reported to be more common than previously recognized.^2,4

Although iatrogenic nerve injuries are in general being recognized,^1,2,4 reports of greater auricular nerve injuries are limited. The greater auricular nerve is a superficial cutaneous nerve that arises from the cervical plexus at the C2 and C3 spinal nerves, obliquely crosses the sternocleidomastoid muscle, and splits into anterior and posterior portions that innervate the skin over the mastoid process and parotid gland.^5,6 In particular, as illustrated by Ginsberg and Eicher⁶ (Figure 1), its superficial anatomy lies very near where a headrest is positioned during arthroscopic surgery, and increased pressure on the nerve throughout arthroscopic shoulder surgery may lead to neurapraxia.^6,7 In 2 case series, authors reported on a total of 5 patients who had greater auricular nerve palsy after uncomplicated shoulder surgery using beach-chair positioning and a horseshoe headrest.^7,8 The authors attributed these palsies to the horseshoe headrest, which they believed was compressing the greater auricular nerve during the entire surgery.^7,8 However, standard universal headrests, which are thought to distribute pressures that would theoretically place the greater auricular nerve at risk for palsy, previously had not been described as contributing to palsy of the greater auricular nerve.

In this article, we report on a case of greater auricular nerve palsy that occurred after the patient’s anterior-inferior and posterior-inferior labral tear was arthroscopically repaired using beach-chair positioning and a standard universal headrest. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

An 18-year-old right-hand–dominant high school American football player was referred for orthopedic evaluation of left chronic glenohumeral instability after 6 months of physical therapy. Physical examination revealed a positive apprehension test with the shoulder abducted and externally rotated at 90° and a positive relocation test. The patient complained of pain and instability when his arm was placed in a cross-chest adducted position and a posteroinferiorly directed axial load was applied. Magnetic resonance arthrogram showed an anterior-inferior labral Bankart tear with a small Hill-Sachs lesion to the humeral head but did not clearly reveal the posterior-inferior labral tear. Because of persistent left shoulder instability with most overhead activities and continued pain, the patient decided to undergo left shoulder arthroscopic Bankart repair with inferior capsular shift and posterior-inferior labral repair with capsulorraphy. He had no significant past medical history or known drug allergies.

The patient was placed in the standard beach-chair position: upright at 45° to the floor, hips flexed at 60°, knees flexed at 30°.¹ Pneumatic compression devices were placed on his lower extremities. His head was secured in neutral position to a standard universal headrest (model A-90026; Allen Medical Systems, Acton, Massachusetts) (Figures 2, 3). Care was taken to protect the deep neurovascular structures and bony prominences throughout. The patient was in this position for 122 minutes of the operation, from positioning and draping to wound closure and dressing application. Before draping, the anesthesiologist, head nurse, and circulating nurse ensured that head and neck were in neutral position. The anesthesiologist monitored positioning throughout the perioperative period to ensure head and neck were in neutral, and the head did not need to be repositioned during surgery. Standard preoperative intravenous antibiotics were given.

General anesthesia and postoperative interscalene block were used. Standard preparation and draping were performed. Three standard arthroscopic portal incisions were used: posterior, anterior, and anterosuperolateral. Findings included extensive labral pathology, small bony Hill-Sachs lesion to humeral head, small bony anterior glenoid deficiency, and deficient anterior-inferior and posterior-inferior labral remnant. These were repaired arthroscopically in a standard fashion using bioabsorbable suture anchors. There were no arthroscopic complications. After surgery, a standard well-fitted shoulder immobilizer was placed. The anesthesiologist provided interscalene regional analgesia (15 mL of bupivacaine 0.5%) in the recovery area after surgery.

Postoperative neurovascular examination in the recovery room revealed no discomfort. The patient was discharged the same day. At a scheduled 1-week follow-up, he complained of numbness and dysesthesia on the left side of the greater auricular nerve distribution. A diagnosis of greater auricular nerve palsy was made by physical examination; the symptoms were along the classic greater auricular nerve distribution affecting the lower face and ear (Figure 4). The patient had no pain, skin lesions, or soft-tissue swelling. Otolaryngology confirmed the diagnosis and recommended observation-only treatment of symptoms. Symptoms lessened over the next 3 months, and the altered sensation resolved without deficit by 6 months. In addition, by 6 months the patient had returned to full activities (including collision sports) pain-free and with normal left shoulder function. Because symptoms continued to improve, the patient was followed with clinical observation, and a formal work-up was not necessary.

Discussion

The most important finding in this case is the greater auricular nerve palsy that occurred after arthroscopic anterior-inferior and posterior-inferior labral repairs in beach-chair positioning. This greater auricular nerve palsy was the first encountered by Dr. Foad, who over 17 years in a primarily shoulder practice setting has used beach-chair positioning exclusively. Previous reports have described a palsy occurring after arthroscopic shoulder surgery using beach-chair positioning and a horseshoe headrest.^7,8 Ng and Page⁷ discontinued and recommended against use of this headrest because of the complications of the palsy, and Park and Kim⁸ recommended a headrest redesign. We think the present case report is the first to describe a greater auricular nerve palsy that occurred after arthroscopic surgery using a standard universal headrest, which theoretically should prevent compression of the greater auricular nerve. Increased awareness of the possibility of greater auricular nerve palsy, even when proper precautions are taken,¹ is therefore warranted.

Based on the location of our patient’s palsy, we think his paralysis was most likely the result of nerve compression by the headrest during the shoulder surgery. Other factors, though unlikely, may have played a role. These include operative time (increases duration of nerve compression) and head positioning. However, 122 minutes is not unusually long for a patient’s head to be in this position during a procedure, and over the past 10 years the same anesthesiologist, head nurse, and circulating nurse have routinely used the same beach-chair positioning and headrest for Dr. Foad’s patients. Second, the postoperative interscalene block theoretically could have caused the palsy, but we think this is unlikely, as the block is placed lower on the neck, at the C6 level, and the greater auricular nerve branches off the C2–C3 spinal nerves. As described by Rains and colleagues,⁹ other authors have reported transient neuropathies to the brachial plexus, which originates in the C5–C8 region, but not to the greater auricular nerve. Last, it cannot be ruled out that a variant of the greater auricular nerve could have played a role, given the variation in the greater auricular nerve.^10,11 However, Brennan and colleagues¹⁰ reported that 2 of 25 neck dissections involved a variant in which the anterior division of the greater auricular nerve passed into the submandibular triangle and joined the mandibular region of the facial nerve. Stimulation of this nerve resulted in activity of the depressor of the lower lip, which was not the location of our patient’s palsy. In addition, our patient’s symptoms followed a classic nerve distribution of the greater auricular nerve (Figures 1, 4), which would seem to decrease the likelihood that a variant was the source of the palsy.

The superficial nature of the greater auricular nerve, which runs roughly parallel with the sternocleidomastoid muscle and innervates much of the superficial region of the skin over the mastoid, parotid gland, and mandible,^5-7 theoretically places the nerve at risk for compressive forces from the headrest during arthroscopic shoulder surgery. Skyhar and colleagues³ first described beach-chair positioning as an alternative to lateral decubitus positioning, which had been reported to result in neurologic injury in about 10% of surgical cases.⁹ The theoretical advantages of beach-chair positioning are lack of traction needed and ease of setup, which would therefore decrease the possibility of neuropathy.^1,3 However, as seen in this and other case reports,^7,8 greater auricular nerve neuropathy should still be considered a possible complication, even when using beach-chair positioning.

Besides neuropathy after arthroscopic shoulder surgery, as described in previous case reports^7,8 and in the present report, greater auricular nerve injury has been described as arising from other stimuli. Greater auricular nerve injury has arisen after perineural tumor metastasis,⁶ neuroma of greater auricular nerve after endolympathic shunt surgery,¹² internal fixation of mandibular condyle,¹³ and carotid endarterectomy.^14,15 Given the superficial nature of the greater auricular nerve, it may not be all that surprising that a palsy could also develop after headrest compression during arthroscopic shoulder surgery.

This case report brings to light a possible complication of greater auricular nerve palsy during arthroscopic shoulder surgery using beach-chair positioning and a standard universal headrest. Studies should now investigate whether greater auricular nerve palsy is more common than realized, especially with regard to specific headrests in beach-chair positioning. For now, though, Dr. Foad’s intention is not to change to a different headrest or discontinue beach-chair positioning but to draw attention to this rare complication. Additional attention should be given to the location of the headrest in relation to the greater auricular nerve, especially in cases in which operative time may be longer.

Conclusion

We have reported a greater auricular nerve palsy that occurred after arthroscopic shoulder surgery for an anterior-inferior and posterior-inferior labral tear. This is the first report of a greater auricular nerve palsy occurring with beach-chair positioning and a standard universal headrest. Symptoms resolved within 6 months. New studies should investigate the incidence of greater auricular nerve palsy after arthroscopic shoulder surgery.

Anterior-inferior and posterior-inferior labral tears are common injuries treated with arthroscopic surgery¹ typically performed with beach-chair^2,3 or lateral decubitus^1,2 positioning and variable headrest positioning. Iatrogenic nerve damage that occurs after arthroscopic shoulder surgery—including damage to the suprascapular, axillary, musculocutaneous, subscapular, and spinal accessory nerves—has recently been reported to be more common than previously recognized.^2,4

Although iatrogenic nerve injuries are in general being recognized,^1,2,4 reports of greater auricular nerve injuries are limited. The greater auricular nerve is a superficial cutaneous nerve that arises from the cervical plexus at the C2 and C3 spinal nerves, obliquely crosses the sternocleidomastoid muscle, and splits into anterior and posterior portions that innervate the skin over the mastoid process and parotid gland.^5,6 In particular, as illustrated by Ginsberg and Eicher⁶ (Figure 1), its superficial anatomy lies very near where a headrest is positioned during arthroscopic surgery, and increased pressure on the nerve throughout arthroscopic shoulder surgery may lead to neurapraxia.^6,7 In 2 case series, authors reported on a total of 5 patients who had greater auricular nerve palsy after uncomplicated shoulder surgery using beach-chair positioning and a horseshoe headrest.^7,8 The authors attributed these palsies to the horseshoe headrest, which they believed was compressing the greater auricular nerve during the entire surgery.^7,8 However, standard universal headrests, which are thought to distribute pressures that would theoretically place the greater auricular nerve at risk for palsy, previously had not been described as contributing to palsy of the greater auricular nerve.

In this article, we report on a case of greater auricular nerve palsy that occurred after the patient’s anterior-inferior and posterior-inferior labral tear was arthroscopically repaired using beach-chair positioning and a standard universal headrest. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

An 18-year-old right-hand–dominant high school American football player was referred for orthopedic evaluation of left chronic glenohumeral instability after 6 months of physical therapy. Physical examination revealed a positive apprehension test with the shoulder abducted and externally rotated at 90° and a positive relocation test. The patient complained of pain and instability when his arm was placed in a cross-chest adducted position and a posteroinferiorly directed axial load was applied. Magnetic resonance arthrogram showed an anterior-inferior labral Bankart tear with a small Hill-Sachs lesion to the humeral head but did not clearly reveal the posterior-inferior labral tear. Because of persistent left shoulder instability with most overhead activities and continued pain, the patient decided to undergo left shoulder arthroscopic Bankart repair with inferior capsular shift and posterior-inferior labral repair with capsulorraphy. He had no significant past medical history or known drug allergies.

The patient was placed in the standard beach-chair position: upright at 45° to the floor, hips flexed at 60°, knees flexed at 30°.¹ Pneumatic compression devices were placed on his lower extremities. His head was secured in neutral position to a standard universal headrest (model A-90026; Allen Medical Systems, Acton, Massachusetts) (Figures 2, 3). Care was taken to protect the deep neurovascular structures and bony prominences throughout. The patient was in this position for 122 minutes of the operation, from positioning and draping to wound closure and dressing application. Before draping, the anesthesiologist, head nurse, and circulating nurse ensured that head and neck were in neutral position. The anesthesiologist monitored positioning throughout the perioperative period to ensure head and neck were in neutral, and the head did not need to be repositioned during surgery. Standard preoperative intravenous antibiotics were given.

General anesthesia and postoperative interscalene block were used. Standard preparation and draping were performed. Three standard arthroscopic portal incisions were used: posterior, anterior, and anterosuperolateral. Findings included extensive labral pathology, small bony Hill-Sachs lesion to humeral head, small bony anterior glenoid deficiency, and deficient anterior-inferior and posterior-inferior labral remnant. These were repaired arthroscopically in a standard fashion using bioabsorbable suture anchors. There were no arthroscopic complications. After surgery, a standard well-fitted shoulder immobilizer was placed. The anesthesiologist provided interscalene regional analgesia (15 mL of bupivacaine 0.5%) in the recovery area after surgery.

Postoperative neurovascular examination in the recovery room revealed no discomfort. The patient was discharged the same day. At a scheduled 1-week follow-up, he complained of numbness and dysesthesia on the left side of the greater auricular nerve distribution. A diagnosis of greater auricular nerve palsy was made by physical examination; the symptoms were along the classic greater auricular nerve distribution affecting the lower face and ear (Figure 4). The patient had no pain, skin lesions, or soft-tissue swelling. Otolaryngology confirmed the diagnosis and recommended observation-only treatment of symptoms. Symptoms lessened over the next 3 months, and the altered sensation resolved without deficit by 6 months. In addition, by 6 months the patient had returned to full activities (including collision sports) pain-free and with normal left shoulder function. Because symptoms continued to improve, the patient was followed with clinical observation, and a formal work-up was not necessary.

Discussion

The most important finding in this case is the greater auricular nerve palsy that occurred after arthroscopic anterior-inferior and posterior-inferior labral repairs in beach-chair positioning. This greater auricular nerve palsy was the first encountered by Dr. Foad, who over 17 years in a primarily shoulder practice setting has used beach-chair positioning exclusively. Previous reports have described a palsy occurring after arthroscopic shoulder surgery using beach-chair positioning and a horseshoe headrest.^7,8 Ng and Page⁷ discontinued and recommended against use of this headrest because of the complications of the palsy, and Park and Kim⁸ recommended a headrest redesign. We think the present case report is the first to describe a greater auricular nerve palsy that occurred after arthroscopic surgery using a standard universal headrest, which theoretically should prevent compression of the greater auricular nerve. Increased awareness of the possibility of greater auricular nerve palsy, even when proper precautions are taken,¹ is therefore warranted.

Based on the location of our patient’s palsy, we think his paralysis was most likely the result of nerve compression by the headrest during the shoulder surgery. Other factors, though unlikely, may have played a role. These include operative time (increases duration of nerve compression) and head positioning. However, 122 minutes is not unusually long for a patient’s head to be in this position during a procedure, and over the past 10 years the same anesthesiologist, head nurse, and circulating nurse have routinely used the same beach-chair positioning and headrest for Dr. Foad’s patients. Second, the postoperative interscalene block theoretically could have caused the palsy, but we think this is unlikely, as the block is placed lower on the neck, at the C6 level, and the greater auricular nerve branches off the C2–C3 spinal nerves. As described by Rains and colleagues,⁹ other authors have reported transient neuropathies to the brachial plexus, which originates in the C5–C8 region, but not to the greater auricular nerve. Last, it cannot be ruled out that a variant of the greater auricular nerve could have played a role, given the variation in the greater auricular nerve.^10,11 However, Brennan and colleagues¹⁰ reported that 2 of 25 neck dissections involved a variant in which the anterior division of the greater auricular nerve passed into the submandibular triangle and joined the mandibular region of the facial nerve. Stimulation of this nerve resulted in activity of the depressor of the lower lip, which was not the location of our patient’s palsy. In addition, our patient’s symptoms followed a classic nerve distribution of the greater auricular nerve (Figures 1, 4), which would seem to decrease the likelihood that a variant was the source of the palsy.

The superficial nature of the greater auricular nerve, which runs roughly parallel with the sternocleidomastoid muscle and innervates much of the superficial region of the skin over the mastoid, parotid gland, and mandible,^5-7 theoretically places the nerve at risk for compressive forces from the headrest during arthroscopic shoulder surgery. Skyhar and colleagues³ first described beach-chair positioning as an alternative to lateral decubitus positioning, which had been reported to result in neurologic injury in about 10% of surgical cases.⁹ The theoretical advantages of beach-chair positioning are lack of traction needed and ease of setup, which would therefore decrease the possibility of neuropathy.^1,3 However, as seen in this and other case reports,^7,8 greater auricular nerve neuropathy should still be considered a possible complication, even when using beach-chair positioning.

Besides neuropathy after arthroscopic shoulder surgery, as described in previous case reports^7,8 and in the present report, greater auricular nerve injury has been described as arising from other stimuli. Greater auricular nerve injury has arisen after perineural tumor metastasis,⁶ neuroma of greater auricular nerve after endolympathic shunt surgery,¹² internal fixation of mandibular condyle,¹³ and carotid endarterectomy.^14,15 Given the superficial nature of the greater auricular nerve, it may not be all that surprising that a palsy could also develop after headrest compression during arthroscopic shoulder surgery.

This case report brings to light a possible complication of greater auricular nerve palsy during arthroscopic shoulder surgery using beach-chair positioning and a standard universal headrest. Studies should now investigate whether greater auricular nerve palsy is more common than realized, especially with regard to specific headrests in beach-chair positioning. For now, though, Dr. Foad’s intention is not to change to a different headrest or discontinue beach-chair positioning but to draw attention to this rare complication. Additional attention should be given to the location of the headrest in relation to the greater auricular nerve, especially in cases in which operative time may be longer.

Conclusion

We have reported a greater auricular nerve palsy that occurred after arthroscopic shoulder surgery for an anterior-inferior and posterior-inferior labral tear. This is the first report of a greater auricular nerve palsy occurring with beach-chair positioning and a standard universal headrest. Symptoms resolved within 6 months. New studies should investigate the incidence of greater auricular nerve palsy after arthroscopic shoulder surgery.

Anterior-inferior and posterior-inferior labral tears are common injuries treated with arthroscopic surgery¹ typically performed with beach-chair^2,3 or lateral decubitus^1,2 positioning and variable headrest positioning. Iatrogenic nerve damage that occurs after arthroscopic shoulder surgery—including damage to the suprascapular, axillary, musculocutaneous, subscapular, and spinal accessory nerves—has recently been reported to be more common than previously recognized.^2,4

Although iatrogenic nerve injuries are in general being recognized,^1,2,4 reports of greater auricular nerve injuries are limited. The greater auricular nerve is a superficial cutaneous nerve that arises from the cervical plexus at the C2 and C3 spinal nerves, obliquely crosses the sternocleidomastoid muscle, and splits into anterior and posterior portions that innervate the skin over the mastoid process and parotid gland.^5,6 In particular, as illustrated by Ginsberg and Eicher⁶ (Figure 1), its superficial anatomy lies very near where a headrest is positioned during arthroscopic surgery, and increased pressure on the nerve throughout arthroscopic shoulder surgery may lead to neurapraxia.^6,7 In 2 case series, authors reported on a total of 5 patients who had greater auricular nerve palsy after uncomplicated shoulder surgery using beach-chair positioning and a horseshoe headrest.^7,8 The authors attributed these palsies to the horseshoe headrest, which they believed was compressing the greater auricular nerve during the entire surgery.^7,8 However, standard universal headrests, which are thought to distribute pressures that would theoretically place the greater auricular nerve at risk for palsy, previously had not been described as contributing to palsy of the greater auricular nerve.

In this article, we report on a case of greater auricular nerve palsy that occurred after the patient’s anterior-inferior and posterior-inferior labral tear was arthroscopically repaired using beach-chair positioning and a standard universal headrest. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

An 18-year-old right-hand–dominant high school American football player was referred for orthopedic evaluation of left chronic glenohumeral instability after 6 months of physical therapy. Physical examination revealed a positive apprehension test with the shoulder abducted and externally rotated at 90° and a positive relocation test. The patient complained of pain and instability when his arm was placed in a cross-chest adducted position and a posteroinferiorly directed axial load was applied. Magnetic resonance arthrogram showed an anterior-inferior labral Bankart tear with a small Hill-Sachs lesion to the humeral head but did not clearly reveal the posterior-inferior labral tear. Because of persistent left shoulder instability with most overhead activities and continued pain, the patient decided to undergo left shoulder arthroscopic Bankart repair with inferior capsular shift and posterior-inferior labral repair with capsulorraphy. He had no significant past medical history or known drug allergies.

The patient was placed in the standard beach-chair position: upright at 45° to the floor, hips flexed at 60°, knees flexed at 30°.¹ Pneumatic compression devices were placed on his lower extremities. His head was secured in neutral position to a standard universal headrest (model A-90026; Allen Medical Systems, Acton, Massachusetts) (Figures 2, 3). Care was taken to protect the deep neurovascular structures and bony prominences throughout. The patient was in this position for 122 minutes of the operation, from positioning and draping to wound closure and dressing application. Before draping, the anesthesiologist, head nurse, and circulating nurse ensured that head and neck were in neutral position. The anesthesiologist monitored positioning throughout the perioperative period to ensure head and neck were in neutral, and the head did not need to be repositioned during surgery. Standard preoperative intravenous antibiotics were given.

General anesthesia and postoperative interscalene block were used. Standard preparation and draping were performed. Three standard arthroscopic portal incisions were used: posterior, anterior, and anterosuperolateral. Findings included extensive labral pathology, small bony Hill-Sachs lesion to humeral head, small bony anterior glenoid deficiency, and deficient anterior-inferior and posterior-inferior labral remnant. These were repaired arthroscopically in a standard fashion using bioabsorbable suture anchors. There were no arthroscopic complications. After surgery, a standard well-fitted shoulder immobilizer was placed. The anesthesiologist provided interscalene regional analgesia (15 mL of bupivacaine 0.5%) in the recovery area after surgery.

Postoperative neurovascular examination in the recovery room revealed no discomfort. The patient was discharged the same day. At a scheduled 1-week follow-up, he complained of numbness and dysesthesia on the left side of the greater auricular nerve distribution. A diagnosis of greater auricular nerve palsy was made by physical examination; the symptoms were along the classic greater auricular nerve distribution affecting the lower face and ear (Figure 4). The patient had no pain, skin lesions, or soft-tissue swelling. Otolaryngology confirmed the diagnosis and recommended observation-only treatment of symptoms. Symptoms lessened over the next 3 months, and the altered sensation resolved without deficit by 6 months. In addition, by 6 months the patient had returned to full activities (including collision sports) pain-free and with normal left shoulder function. Because symptoms continued to improve, the patient was followed with clinical observation, and a formal work-up was not necessary.

Discussion

The most important finding in this case is the greater auricular nerve palsy that occurred after arthroscopic anterior-inferior and posterior-inferior labral repairs in beach-chair positioning. This greater auricular nerve palsy was the first encountered by Dr. Foad, who over 17 years in a primarily shoulder practice setting has used beach-chair positioning exclusively. Previous reports have described a palsy occurring after arthroscopic shoulder surgery using beach-chair positioning and a horseshoe headrest.^7,8 Ng and Page⁷ discontinued and recommended against use of this headrest because of the complications of the palsy, and Park and Kim⁸ recommended a headrest redesign. We think the present case report is the first to describe a greater auricular nerve palsy that occurred after arthroscopic surgery using a standard universal headrest, which theoretically should prevent compression of the greater auricular nerve. Increased awareness of the possibility of greater auricular nerve palsy, even when proper precautions are taken,¹ is therefore warranted.

Based on the location of our patient’s palsy, we think his paralysis was most likely the result of nerve compression by the headrest during the shoulder surgery. Other factors, though unlikely, may have played a role. These include operative time (increases duration of nerve compression) and head positioning. However, 122 minutes is not unusually long for a patient’s head to be in this position during a procedure, and over the past 10 years the same anesthesiologist, head nurse, and circulating nurse have routinely used the same beach-chair positioning and headrest for Dr. Foad’s patients. Second, the postoperative interscalene block theoretically could have caused the palsy, but we think this is unlikely, as the block is placed lower on the neck, at the C6 level, and the greater auricular nerve branches off the C2–C3 spinal nerves. As described by Rains and colleagues,⁹ other authors have reported transient neuropathies to the brachial plexus, which originates in the C5–C8 region, but not to the greater auricular nerve. Last, it cannot be ruled out that a variant of the greater auricular nerve could have played a role, given the variation in the greater auricular nerve.^10,11 However, Brennan and colleagues¹⁰ reported that 2 of 25 neck dissections involved a variant in which the anterior division of the greater auricular nerve passed into the submandibular triangle and joined the mandibular region of the facial nerve. Stimulation of this nerve resulted in activity of the depressor of the lower lip, which was not the location of our patient’s palsy. In addition, our patient’s symptoms followed a classic nerve distribution of the greater auricular nerve (Figures 1, 4), which would seem to decrease the likelihood that a variant was the source of the palsy.

The superficial nature of the greater auricular nerve, which runs roughly parallel with the sternocleidomastoid muscle and innervates much of the superficial region of the skin over the mastoid, parotid gland, and mandible,^5-7 theoretically places the nerve at risk for compressive forces from the headrest during arthroscopic shoulder surgery. Skyhar and colleagues³ first described beach-chair positioning as an alternative to lateral decubitus positioning, which had been reported to result in neurologic injury in about 10% of surgical cases.⁹ The theoretical advantages of beach-chair positioning are lack of traction needed and ease of setup, which would therefore decrease the possibility of neuropathy.^1,3 However, as seen in this and other case reports,^7,8 greater auricular nerve neuropathy should still be considered a possible complication, even when using beach-chair positioning.

Besides neuropathy after arthroscopic shoulder surgery, as described in previous case reports^7,8 and in the present report, greater auricular nerve injury has been described as arising from other stimuli. Greater auricular nerve injury has arisen after perineural tumor metastasis,⁶ neuroma of greater auricular nerve after endolympathic shunt surgery,¹² internal fixation of mandibular condyle,¹³ and carotid endarterectomy.^14,15 Given the superficial nature of the greater auricular nerve, it may not be all that surprising that a palsy could also develop after headrest compression during arthroscopic shoulder surgery.

This case report brings to light a possible complication of greater auricular nerve palsy during arthroscopic shoulder surgery using beach-chair positioning and a standard universal headrest. Studies should now investigate whether greater auricular nerve palsy is more common than realized, especially with regard to specific headrests in beach-chair positioning. For now, though, Dr. Foad’s intention is not to change to a different headrest or discontinue beach-chair positioning but to draw attention to this rare complication. Additional attention should be given to the location of the headrest in relation to the greater auricular nerve, especially in cases in which operative time may be longer.

Conclusion

We have reported a greater auricular nerve palsy that occurred after arthroscopic shoulder surgery for an anterior-inferior and posterior-inferior labral tear. This is the first report of a greater auricular nerve palsy occurring with beach-chair positioning and a standard universal headrest. Symptoms resolved within 6 months. New studies should investigate the incidence of greater auricular nerve palsy after arthroscopic shoulder surgery.

THE CASE

A 31-year-old man came to an internal medicine clinic because he’d been losing weight over the past 2 years and hadn’t been able to regain any weight despite eating properly. Our patient was born in Ethiopia, but had been living in Canada for 6 years. He reported a remote history of 2 episodes of diarrhea.

His physical exam was normal and laboratory results revealed mild eosinophilia of 0.6 × 10⁹/L (normal range, <0.45 × 10⁹/L). Additional tests (including complete blood count, electrolytes, liver panel, thyrotropin, and blood smear) revealed no apparent metabolic causes of the patient’s weight loss. Stool analysis (3 exams) was negative for ova and parasites.

THE DIAGNOSIS

Because our patient was born in Ethiopia, we did serologic testing for Strongyloides, which was positive (enzyme-linked immunosorbent assay for immunoglobulin G antibodies [IgG-ELISA] was 2.9; positive is >2.1). We diagnosed strongyloidiasis in this patient.

DISCUSSION

Strongyloidiasis is an infection caused by the parasite Strongyloides stercoralis.¹ It affects an estimated 30 to 100 million people worldwide, mainly in Africa, Southeast Asia, Central America, and South America, but it also can occur in temperate climates.²Strongyloides is a soil-transmitted helminth (parasitic worm). The prevalence of Strongyloides infection among refugee groups in the United States is 1% to 4.3%.^3-5

Although patients with strongyloidiasis are often asymptomatic, they can present with a wide range of nonspecific symptoms. In the acute stage, patients may develop signs and symptoms including cough, wheeze, abdominal pain, weight loss, diarrhea, pruritus ani, and larva currens.² Respiratory symptoms, including tracheal irritation and a dry cough, are often confused with asthma. In the generally asymptomatic chronic stage, patients may develop gastrointestinal complaints, such as epigastric pain and heartburn.⁶

Hyperinfection syndrome can occur when patients with subclinical infection receive high doses of corticosteroids for asthma or chronic obstructive pulmonary disease exacerbations. Risk of hyperinfection is increased among immunocompromised patients with human T lymphotropic virus type-1 (HTLV-1),⁷ as well as in patients with malignancies, malnutrition, and alcohol use disorder. Eosinophilia is often absent in patients with hyperinfection, and stool examination results are almost always positive.⁸

Who to screen, how to make the diagnosis

Suspect strongyloidiasis infection in immigrants, refugees, and travelers from endemic regions who have eosinophilia. The presence of eosinophilia in immigrants, refugees, and travelers from endemic regions should alert clinicians to the possibility of an underlying helminth infection. However, because eosinophilia occurs intermittently in response to tissue invasion, absence of eosinophilia does not exclude strongyloidiasis.

The Canadian Collaboration for Immigrants and Refugee Health (CCIRH) recommends using serologic testing to screen for Strongyloides in all newly arrived refugees from low-income countries in Southeast Asia and Africa.⁹ The CCIRH also advises that while data on the burden of strongyloidiasis in non-refugee immigrant populations is limited, you should consider screening foreign-born individuals who have lived in endemic areas, have symptoms and/or signs of Strongyloides infection, and/or have evidence of eosinophilia.⁹ Because the risk of hyperinfection is increased in immunocompromised individuals, screening should be done to detect Strongyloides infection before starting chemotherapy and before initiating corticosteroids in patients from endemic areas.¹⁰

Diagnostic methods. Stool examination⁶ and IgG-ELISA² are the main methods used to diagnose strongyloidiasis. However, traditional stool examinations have low sensitivity, and it may require up to 7 stool exams to reach a sensitivity of 100%,⁶ which could explain why our patient’s stool analysis was negative for parasites. In our experience, a positive serology result should always be assumed to indicate an active infection unless there is a well documented history of prior therapy. (In such cases, a positive serology result could represent persistent antibodies following therapy.)

First-line therapy and alternative treatment

All patients with strongyloidiasis, regardless of whether they are symptomatic, must be treated to prevent possible late-onset disseminated disease and hyperinfection.⁹ The Centers for Disease Control and Prevention recommends one to 2 doses of ivermectin 200 mcg/kg as first-line therapy or albendazole 400 mg twice daily for 3 days as an alternative treatment (TABLE).¹¹ Ivermectin cures more than 95% of cases.¹² Albendazole has lower efficacy (78%).¹³ Some experts recommend administering the 2 doses of ivermectin 2 weeks apart to allow enough time for the parasite to migrate to the gut.⁴

Consider referral to an infectious disease specialist for patients coinfected with HTLV-1, as well as those who are immunocompromised. Coinfection with HTLV-1 (which is endemic in areas where Strongyloides also is
endemic) modifies patients’ immune response and can complicate treatment.⁹ Clinicians should screen strongyloidiasis patients for HTLV-1 if they come from high-prevalence areas and/or have persistent strongyloidiasis that responds poorly to antiparasitic treatment.⁹

Consider referral to an infectious disease specialist for patients coinfected with
HTLV-1, as well as those who are immunocompromised. Such referral also may be appropriate for patients from countries where loa loa is endemic, because encephalopathy has occurred in patients coinfected with loa loa who were treated with ivermectin.¹⁰

Our patient was treated with 2 doses of ivermectin 200 mcg/kg, 2 weeks apart. Four months later, his eosinophilia had resolved, his IgG-ELISA dropped to 0.37, and he had gained 2.5 pounds.

THE TAKEAWAY

Strongyloidiasis is an infection caused by the parasitic worm Strongyloides stercoralis that is most common in tropical or subtropical areas. It can be asymptomatic or present with a wide range of nonspecific signs and symptoms, such as eosinophilia, cough, wheeze, abdominal pain, weight loss, diarrhea, pruritus ani, and larva currens. It is diagnosed by stool examination and serologic testing. Ivermectin is first-line therapy; albendazole is an alternative.

THE CASE

A 31-year-old man came to an internal medicine clinic because he’d been losing weight over the past 2 years and hadn’t been able to regain any weight despite eating properly. Our patient was born in Ethiopia, but had been living in Canada for 6 years. He reported a remote history of 2 episodes of diarrhea.

His physical exam was normal and laboratory results revealed mild eosinophilia of 0.6 × 10⁹/L (normal range, <0.45 × 10⁹/L). Additional tests (including complete blood count, electrolytes, liver panel, thyrotropin, and blood smear) revealed no apparent metabolic causes of the patient’s weight loss. Stool analysis (3 exams) was negative for ova and parasites.

THE DIAGNOSIS

Because our patient was born in Ethiopia, we did serologic testing for Strongyloides, which was positive (enzyme-linked immunosorbent assay for immunoglobulin G antibodies [IgG-ELISA] was 2.9; positive is >2.1). We diagnosed strongyloidiasis in this patient.

DISCUSSION

Strongyloidiasis is an infection caused by the parasite Strongyloides stercoralis.¹ It affects an estimated 30 to 100 million people worldwide, mainly in Africa, Southeast Asia, Central America, and South America, but it also can occur in temperate climates.²Strongyloides is a soil-transmitted helminth (parasitic worm). The prevalence of Strongyloides infection among refugee groups in the United States is 1% to 4.3%.^3-5

Although patients with strongyloidiasis are often asymptomatic, they can present with a wide range of nonspecific symptoms. In the acute stage, patients may develop signs and symptoms including cough, wheeze, abdominal pain, weight loss, diarrhea, pruritus ani, and larva currens.² Respiratory symptoms, including tracheal irritation and a dry cough, are often confused with asthma. In the generally asymptomatic chronic stage, patients may develop gastrointestinal complaints, such as epigastric pain and heartburn.⁶

Hyperinfection syndrome can occur when patients with subclinical infection receive high doses of corticosteroids for asthma or chronic obstructive pulmonary disease exacerbations. Risk of hyperinfection is increased among immunocompromised patients with human T lymphotropic virus type-1 (HTLV-1),⁷ as well as in patients with malignancies, malnutrition, and alcohol use disorder. Eosinophilia is often absent in patients with hyperinfection, and stool examination results are almost always positive.⁸

Who to screen, how to make the diagnosis

Suspect strongyloidiasis infection in immigrants, refugees, and travelers from endemic regions who have eosinophilia. The presence of eosinophilia in immigrants, refugees, and travelers from endemic regions should alert clinicians to the possibility of an underlying helminth infection. However, because eosinophilia occurs intermittently in response to tissue invasion, absence of eosinophilia does not exclude strongyloidiasis.

The Canadian Collaboration for Immigrants and Refugee Health (CCIRH) recommends using serologic testing to screen for Strongyloides in all newly arrived refugees from low-income countries in Southeast Asia and Africa.⁹ The CCIRH also advises that while data on the burden of strongyloidiasis in non-refugee immigrant populations is limited, you should consider screening foreign-born individuals who have lived in endemic areas, have symptoms and/or signs of Strongyloides infection, and/or have evidence of eosinophilia.⁹ Because the risk of hyperinfection is increased in immunocompromised individuals, screening should be done to detect Strongyloides infection before starting chemotherapy and before initiating corticosteroids in patients from endemic areas.¹⁰

Diagnostic methods. Stool examination⁶ and IgG-ELISA² are the main methods used to diagnose strongyloidiasis. However, traditional stool examinations have low sensitivity, and it may require up to 7 stool exams to reach a sensitivity of 100%,⁶ which could explain why our patient’s stool analysis was negative for parasites. In our experience, a positive serology result should always be assumed to indicate an active infection unless there is a well documented history of prior therapy. (In such cases, a positive serology result could represent persistent antibodies following therapy.)

First-line therapy and alternative treatment

All patients with strongyloidiasis, regardless of whether they are symptomatic, must be treated to prevent possible late-onset disseminated disease and hyperinfection.⁹ The Centers for Disease Control and Prevention recommends one to 2 doses of ivermectin 200 mcg/kg as first-line therapy or albendazole 400 mg twice daily for 3 days as an alternative treatment (TABLE).¹¹ Ivermectin cures more than 95% of cases.¹² Albendazole has lower efficacy (78%).¹³ Some experts recommend administering the 2 doses of ivermectin 2 weeks apart to allow enough time for the parasite to migrate to the gut.⁴

Consider referral to an infectious disease specialist for patients coinfected with HTLV-1, as well as those who are immunocompromised. Coinfection with HTLV-1 (which is endemic in areas where Strongyloides also is
endemic) modifies patients’ immune response and can complicate treatment.⁹ Clinicians should screen strongyloidiasis patients for HTLV-1 if they come from high-prevalence areas and/or have persistent strongyloidiasis that responds poorly to antiparasitic treatment.⁹

Consider referral to an infectious disease specialist for patients coinfected with
HTLV-1, as well as those who are immunocompromised. Such referral also may be appropriate for patients from countries where loa loa is endemic, because encephalopathy has occurred in patients coinfected with loa loa who were treated with ivermectin.¹⁰

Our patient was treated with 2 doses of ivermectin 200 mcg/kg, 2 weeks apart. Four months later, his eosinophilia had resolved, his IgG-ELISA dropped to 0.37, and he had gained 2.5 pounds.

THE TAKEAWAY

Strongyloidiasis is an infection caused by the parasitic worm Strongyloides stercoralis that is most common in tropical or subtropical areas. It can be asymptomatic or present with a wide range of nonspecific signs and symptoms, such as eosinophilia, cough, wheeze, abdominal pain, weight loss, diarrhea, pruritus ani, and larva currens. It is diagnosed by stool examination and serologic testing. Ivermectin is first-line therapy; albendazole is an alternative.

THE CASE

A 31-year-old man came to an internal medicine clinic because he’d been losing weight over the past 2 years and hadn’t been able to regain any weight despite eating properly. Our patient was born in Ethiopia, but had been living in Canada for 6 years. He reported a remote history of 2 episodes of diarrhea.

His physical exam was normal and laboratory results revealed mild eosinophilia of 0.6 × 10⁹/L (normal range, <0.45 × 10⁹/L). Additional tests (including complete blood count, electrolytes, liver panel, thyrotropin, and blood smear) revealed no apparent metabolic causes of the patient’s weight loss. Stool analysis (3 exams) was negative for ova and parasites.

THE DIAGNOSIS

Because our patient was born in Ethiopia, we did serologic testing for Strongyloides, which was positive (enzyme-linked immunosorbent assay for immunoglobulin G antibodies [IgG-ELISA] was 2.9; positive is >2.1). We diagnosed strongyloidiasis in this patient.

DISCUSSION

Strongyloidiasis is an infection caused by the parasite Strongyloides stercoralis.¹ It affects an estimated 30 to 100 million people worldwide, mainly in Africa, Southeast Asia, Central America, and South America, but it also can occur in temperate climates.²Strongyloides is a soil-transmitted helminth (parasitic worm). The prevalence of Strongyloides infection among refugee groups in the United States is 1% to 4.3%.^3-5

Although patients with strongyloidiasis are often asymptomatic, they can present with a wide range of nonspecific symptoms. In the acute stage, patients may develop signs and symptoms including cough, wheeze, abdominal pain, weight loss, diarrhea, pruritus ani, and larva currens.² Respiratory symptoms, including tracheal irritation and a dry cough, are often confused with asthma. In the generally asymptomatic chronic stage, patients may develop gastrointestinal complaints, such as epigastric pain and heartburn.⁶

Hyperinfection syndrome can occur when patients with subclinical infection receive high doses of corticosteroids for asthma or chronic obstructive pulmonary disease exacerbations. Risk of hyperinfection is increased among immunocompromised patients with human T lymphotropic virus type-1 (HTLV-1),⁷ as well as in patients with malignancies, malnutrition, and alcohol use disorder. Eosinophilia is often absent in patients with hyperinfection, and stool examination results are almost always positive.⁸

Who to screen, how to make the diagnosis

Suspect strongyloidiasis infection in immigrants, refugees, and travelers from endemic regions who have eosinophilia. The presence of eosinophilia in immigrants, refugees, and travelers from endemic regions should alert clinicians to the possibility of an underlying helminth infection. However, because eosinophilia occurs intermittently in response to tissue invasion, absence of eosinophilia does not exclude strongyloidiasis.

The Canadian Collaboration for Immigrants and Refugee Health (CCIRH) recommends using serologic testing to screen for Strongyloides in all newly arrived refugees from low-income countries in Southeast Asia and Africa.⁹ The CCIRH also advises that while data on the burden of strongyloidiasis in non-refugee immigrant populations is limited, you should consider screening foreign-born individuals who have lived in endemic areas, have symptoms and/or signs of Strongyloides infection, and/or have evidence of eosinophilia.⁹ Because the risk of hyperinfection is increased in immunocompromised individuals, screening should be done to detect Strongyloides infection before starting chemotherapy and before initiating corticosteroids in patients from endemic areas.¹⁰

Diagnostic methods. Stool examination⁶ and IgG-ELISA² are the main methods used to diagnose strongyloidiasis. However, traditional stool examinations have low sensitivity, and it may require up to 7 stool exams to reach a sensitivity of 100%,⁶ which could explain why our patient’s stool analysis was negative for parasites. In our experience, a positive serology result should always be assumed to indicate an active infection unless there is a well documented history of prior therapy. (In such cases, a positive serology result could represent persistent antibodies following therapy.)

First-line therapy and alternative treatment

All patients with strongyloidiasis, regardless of whether they are symptomatic, must be treated to prevent possible late-onset disseminated disease and hyperinfection.⁹ The Centers for Disease Control and Prevention recommends one to 2 doses of ivermectin 200 mcg/kg as first-line therapy or albendazole 400 mg twice daily for 3 days as an alternative treatment (TABLE).¹¹ Ivermectin cures more than 95% of cases.¹² Albendazole has lower efficacy (78%).¹³ Some experts recommend administering the 2 doses of ivermectin 2 weeks apart to allow enough time for the parasite to migrate to the gut.⁴

Consider referral to an infectious disease specialist for patients coinfected with HTLV-1, as well as those who are immunocompromised. Coinfection with HTLV-1 (which is endemic in areas where Strongyloides also is
endemic) modifies patients’ immune response and can complicate treatment.⁹ Clinicians should screen strongyloidiasis patients for HTLV-1 if they come from high-prevalence areas and/or have persistent strongyloidiasis that responds poorly to antiparasitic treatment.⁹

Consider referral to an infectious disease specialist for patients coinfected with
HTLV-1, as well as those who are immunocompromised. Such referral also may be appropriate for patients from countries where loa loa is endemic, because encephalopathy has occurred in patients coinfected with loa loa who were treated with ivermectin.¹⁰

Our patient was treated with 2 doses of ivermectin 200 mcg/kg, 2 weeks apart. Four months later, his eosinophilia had resolved, his IgG-ELISA dropped to 0.37, and he had gained 2.5 pounds.

THE TAKEAWAY

Strongyloidiasis is an infection caused by the parasitic worm Strongyloides stercoralis that is most common in tropical or subtropical areas. It can be asymptomatic or present with a wide range of nonspecific signs and symptoms, such as eosinophilia, cough, wheeze, abdominal pain, weight loss, diarrhea, pruritus ani, and larva currens. It is diagnosed by stool examination and serologic testing. Ivermectin is first-line therapy; albendazole is an alternative.