SCIENTIFIC ARTICLE
Anteriorly Positioned Ulnar Nerve at the Elbow: A Rare Anatomical Event: Case Report Ellen S. Satteson, MD, Zhongyu Li, MD, PhD
Two patients with an anteriorly positioned ulnar nerve at the elbow, identified during cubital tunnel release, are presented. Upon encountering an empty cubital tunnel, additional dissection found the ulnar nerve to course posterior to and to penetrate through the intermuscular septum 3 to 5 cm proximal to the medial epicondyle. It then ran anterior to the pronator-flexor mass before entering the forearm between the ulnar and the humeral heads of the flexor carpi ulnaris. Although a rare anatomical anomaly, an anteriorly positioned ulnar nerve is potentially an underreported finding. In individuals with cubital tunnel syndrome, diagnosis and surgical treatment may be negatively affected if the surgeon fails to recognize the aberrant anatomy. Upper extremity surgeons should also be mindful of this rare anomaly when performing elbow arthroscopy or medial epicondyle release to prevent inadvertent injury to the nerve. (J Hand Surg Am. 2015;40(5):984e986. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Key words Anterior transposition, cubital tunnel syndrome, ulnar nerve, ulnar neuropathy, clinical anatomy.
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second most common compressive neuropathy of the upper extremity with an estimated incidence of 25 cases per 100,000 individuals.1 Therefore, understanding the anatomy of the ulnar nerve and the surrounding structures that may cause compression is paramount to successful treatment of the condition. Given the multiple possible compression sites contributing to cubital tunnel syndrome, it is critical that those involved with its diagnosis and treatment have an in-depth understanding of the anatomy of the ulnar nerve in this region. This includes a working knowledge of potential anatomical variants, particularly when proceeding with surgical management. UBITAL TUNNEL SYNDROME IS THE
From the Department of Orthopaedic Surgery, Wake Forest Baptist Medical Center, Winston-Salem, NC. Received for publication August 28, 2014; accepted in revised form February 5, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Zhongyu Li, MD, PhD, Department of Orthopaedic Surgery, Wake Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157; e-mail: [email protected]. 0363-5023/15/4005-0018$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.02.006
984
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Ó 2015 ASSH
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Published by Elsevier, Inc. All rights reserved.
We present 2 cases of anterior positioning of the ulnar nerve at the elbow, an aberrant nerve location discovered at the time of cubital tunnel release. CASE 1 A 66-year-old man presented for evaluation of a oneyear history of left elbow pain with sharp, shooting pain and tingling radiating into his ring and little fingers. He had no previous upper extremity trauma or surgery. Physical examination revealed no gross deformity at the elbow and full range of motion with no instability. He had decreased sensation to light touch on both the ring and the little fingers and 4/5 first dorsal interosseous and abductor digiti minimi strength on the left compared with 5/5 on the right. A Tinel test was positive proximal to the cubital tunnel. Elbow flexion test was also positive. There was no notable subluxation or dislocation of the ulnar nerve during elbow flexion. A nerve conduction study showed ulnar nerve slowing at the elbow. EMG showed markedly reduced motor unit recruitment in the first dorsal interosseous and slightly reduced recruitment in the abductor digiti minimi. Spontaneous fibrillations were noted in both. Ultrasonography is
ANTERIORLY POSITIONED ULNAR NERVE
routinely performed with a nerve conduction study at our institution. In this case, the ultrasound technician reported areas of enlargement but also described areas of the nerve that were difficult to visualize. The locations of these areas were not specified in the report. Given that the patient’s history, physical examination, and electrodiagnostic studies were consistent with severe cubital tunnel syndrome, he was treated with an open cubital tunnel release. A medial incision was made between the medial epicondyle and the olecranon. Dissection into the cubital tunnel failed to identify the ulnar nerve. It was, however, identified proximally, posterior to the intermuscular septum. It penetrated the septum 5 cm proximal to the medial epicondyle, where it appeared to be compressed prior to emerging anteriorly and passing in front of the flexor-pronator muscle mass. Decompression was achieved by releasing the intermuscular septum and brachial fascia. The flexor carpi ulnaris (FCU) fascia and deep flexor-pronator aponeurosis were also divided. After surgery, the patient began the standard regimen of nerve gliding exercises and had complete resolution of his symptoms within 6 weeks.
appeared to be compressed. The FCU fascia and deep flexor-pronator aponeurosis were released. Proximally, the nerve was located anterior to the medial epicondyle. Proximally, it was posterior to and then penetrated through the intermuscular septum 3 cm proximal to the epicondyle where additional decompression was performed. After surgery, she had complete resolution of her paresthesias by her 6-week follow-up appointment. DISCUSSION Classically, the ulnar nerve in the upper arm courses anterior to the medial head of the triceps and posterior to the medial intermuscular septum. It enters the cubital tunnel passing posterior to the medial epicondyle and medial to the olecranon. There it gives off articular branches and motor branches to the FCU and medial half of the flexor digitorum profundus. It then passes between the ulnar and humeral heads of the FCU and into the forearm.2,3 We report 2 cases of an ulnar nerve located anterior to the medial epicondyle. To the best of our knowledge, two similar cases have been reported—a patient with trisomy 132 and a patient with a history of a childhood elbow fracture managed nonsurgically.3 The occurrence of this anatomical variant is rare, but the true occurrence could be underreported because only a relatively small percentage of the population undergoes a procedure such as cubital tunnel release where the aberrant anatomy would be identified. Individuals with an ulnar nerve anterior to the medial epicondyle may, however, pose a challenge to the managing physicians. In one of the previously reported cases, for example, an experienced surgeon was unable to identify the ulnar nerve during cubital tunnel release and had to abort the procedure. The ulnar nerve was found anterior to the medial epicondyle on secondary exploration 3 days later.3 Awareness of this anatomical variant may have spared this patient a second surgical exploration. If the ulnar groove appears to be empty during cubital tunnel release, the surgical incision should be extended, and the ulnar nerve should be sought between the 2 heads of the FCU distally or 3 to 5 cm proximal to the medial epicondyle. The site where the ulnar nerve penetrates through the intermuscular septum can contribute to the compression and should be fully released. Our 2 patients had a positive Tinel sign over the FCU but not right behind the medial epicondyle. Suspicion of an anteriorly located ulnar nerve should be raised if one cannot palpate the ulnar nerve in the ulnar groove. Both our patients had a positive elbow
CASE 2 A healthy 21-year-old, right-handed woman with a history of a right both-bone midforearm fracture 8 years prior that was managed nonsurgically, was referred with an approximately 6-month history of increasing numbness and tingling in her right ring and little fingers that had failed to improve with nonsurgical treatment measures. She reported having had similar symptoms at the time of her initial injury that had resolved spontaneously. She denied subsequent trauma to the extremity. Physical examination revealed decreased sensation to light touch, temperature, and pinprick in the ulnar nerve distribution and a positive elbow flexion test. A Tinel test performed by percussing the entire course of the nerve at the elbow was noted to be positive distal to the cubital tunnel, near the origin of the FCU. Again, no palpable ulnar nerve or nerve subluxation was appreciated. X-rays showed a well-healed both-bone midforearm fracture. Electrodiagnostic studies performed at another facility were unremarkable. Despite normal electrodiagnostic testing, the patient’s symptoms and examination findings were highly suggestive of cubital tunnel syndrome. At the time of open cubital tunnel release, dissection was performed in the interval between the triceps muscle and the intermuscular septum. The ulnar groove was empty. With dissection distally, the ulnar nerve was located between the 2 heads of the FCU where it J Hand Surg Am.
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flexion test. We would have expected this to be negative given the anterior location of the nerve. However, one possible explanation is that further tightening with elbow flexion increased compression at the site where the ulnar nerve penetrated the intermuscular septum. Awareness of this rare anatomical variant is beneficial for elbow surgeons. Although there have been no reported cases of ulnar nerve injury related to this particular anatomical anomaly during elbow arthroscopy, if unrecognized, such patients could be at increased risk of injury to the aberrant ulnar nerve during placement of the superomedial portal. Knowledge of the possible anterior location of the nerve could also be of clinical importance to those performing
J Hand Surg Am.
electrodiagnostic and ultrasonographic testing in the upper extremity. Difficulty visualizing the ulnar nerve on ultrasound in the region of the cubital tunnel should prompt examination of the area anterior to the medial epicondyle to ensure that anterior positioning is not present. REFERENCES 1. Mondelli M, Giannini F, Ballerini M, Ginanneschi F, Martorelli E. Incidence of ulnar neuropathy at the elbow in the province of Siena (Italy). J Neurol Sci. 2005;234(1e2):5e10. 2. Aziz MA. Anatomical defects in a case of trisomy 13 with a D/D translocation. Tetrology. 1980;22(2):217e227. 3. Davis GA. Ulnar nerve volar to medial epicondyle: an anatomical variation. Case illustration. J Neurosurg. 2006;104(4):625.
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Vol. 40, May 2015
Anteriorly Positioned Ulnar Nerve at the Elbow: A Rare Anatomical Event: Case Report Ellen S. Satteson, MD, Zhongyu Li, MD, PhD
Two patients with an anteriorly positioned ulnar nerve at the elbow, identified during cubital tunnel release, are presented. Upon encountering an empty cubital tunnel, additional dissection found the ulnar nerve to course posterior to and to penetrate through the intermuscular septum 3 to 5 cm proximal to the medial epicondyle. It then ran anterior to the pronator-flexor mass before entering the forearm between the ulnar and the humeral heads of the flexor carpi ulnaris. Although a rare anatomical anomaly, an anteriorly positioned ulnar nerve is potentially an underreported finding. In individuals with cubital tunnel syndrome, diagnosis and surgical treatment may be negatively affected if the surgeon fails to recognize the aberrant anatomy. Upper extremity surgeons should also be mindful of this rare anomaly when performing elbow arthroscopy or medial epicondyle release to prevent inadvertent injury to the nerve. (J Hand Surg Am. 2015;40(5):984e986. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Key words Anterior transposition, cubital tunnel syndrome, ulnar nerve, ulnar neuropathy, clinical anatomy.
C
second most common compressive neuropathy of the upper extremity with an estimated incidence of 25 cases per 100,000 individuals.1 Therefore, understanding the anatomy of the ulnar nerve and the surrounding structures that may cause compression is paramount to successful treatment of the condition. Given the multiple possible compression sites contributing to cubital tunnel syndrome, it is critical that those involved with its diagnosis and treatment have an in-depth understanding of the anatomy of the ulnar nerve in this region. This includes a working knowledge of potential anatomical variants, particularly when proceeding with surgical management. UBITAL TUNNEL SYNDROME IS THE
From the Department of Orthopaedic Surgery, Wake Forest Baptist Medical Center, Winston-Salem, NC. Received for publication August 28, 2014; accepted in revised form February 5, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Zhongyu Li, MD, PhD, Department of Orthopaedic Surgery, Wake Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157; e-mail: [email protected]. 0363-5023/15/4005-0018$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.02.006
984
r
Ó 2015 ASSH
r
Published by Elsevier, Inc. All rights reserved.
We present 2 cases of anterior positioning of the ulnar nerve at the elbow, an aberrant nerve location discovered at the time of cubital tunnel release. CASE 1 A 66-year-old man presented for evaluation of a oneyear history of left elbow pain with sharp, shooting pain and tingling radiating into his ring and little fingers. He had no previous upper extremity trauma or surgery. Physical examination revealed no gross deformity at the elbow and full range of motion with no instability. He had decreased sensation to light touch on both the ring and the little fingers and 4/5 first dorsal interosseous and abductor digiti minimi strength on the left compared with 5/5 on the right. A Tinel test was positive proximal to the cubital tunnel. Elbow flexion test was also positive. There was no notable subluxation or dislocation of the ulnar nerve during elbow flexion. A nerve conduction study showed ulnar nerve slowing at the elbow. EMG showed markedly reduced motor unit recruitment in the first dorsal interosseous and slightly reduced recruitment in the abductor digiti minimi. Spontaneous fibrillations were noted in both. Ultrasonography is
ANTERIORLY POSITIONED ULNAR NERVE
routinely performed with a nerve conduction study at our institution. In this case, the ultrasound technician reported areas of enlargement but also described areas of the nerve that were difficult to visualize. The locations of these areas were not specified in the report. Given that the patient’s history, physical examination, and electrodiagnostic studies were consistent with severe cubital tunnel syndrome, he was treated with an open cubital tunnel release. A medial incision was made between the medial epicondyle and the olecranon. Dissection into the cubital tunnel failed to identify the ulnar nerve. It was, however, identified proximally, posterior to the intermuscular septum. It penetrated the septum 5 cm proximal to the medial epicondyle, where it appeared to be compressed prior to emerging anteriorly and passing in front of the flexor-pronator muscle mass. Decompression was achieved by releasing the intermuscular septum and brachial fascia. The flexor carpi ulnaris (FCU) fascia and deep flexor-pronator aponeurosis were also divided. After surgery, the patient began the standard regimen of nerve gliding exercises and had complete resolution of his symptoms within 6 weeks.
appeared to be compressed. The FCU fascia and deep flexor-pronator aponeurosis were released. Proximally, the nerve was located anterior to the medial epicondyle. Proximally, it was posterior to and then penetrated through the intermuscular septum 3 cm proximal to the epicondyle where additional decompression was performed. After surgery, she had complete resolution of her paresthesias by her 6-week follow-up appointment. DISCUSSION Classically, the ulnar nerve in the upper arm courses anterior to the medial head of the triceps and posterior to the medial intermuscular septum. It enters the cubital tunnel passing posterior to the medial epicondyle and medial to the olecranon. There it gives off articular branches and motor branches to the FCU and medial half of the flexor digitorum profundus. It then passes between the ulnar and humeral heads of the FCU and into the forearm.2,3 We report 2 cases of an ulnar nerve located anterior to the medial epicondyle. To the best of our knowledge, two similar cases have been reported—a patient with trisomy 132 and a patient with a history of a childhood elbow fracture managed nonsurgically.3 The occurrence of this anatomical variant is rare, but the true occurrence could be underreported because only a relatively small percentage of the population undergoes a procedure such as cubital tunnel release where the aberrant anatomy would be identified. Individuals with an ulnar nerve anterior to the medial epicondyle may, however, pose a challenge to the managing physicians. In one of the previously reported cases, for example, an experienced surgeon was unable to identify the ulnar nerve during cubital tunnel release and had to abort the procedure. The ulnar nerve was found anterior to the medial epicondyle on secondary exploration 3 days later.3 Awareness of this anatomical variant may have spared this patient a second surgical exploration. If the ulnar groove appears to be empty during cubital tunnel release, the surgical incision should be extended, and the ulnar nerve should be sought between the 2 heads of the FCU distally or 3 to 5 cm proximal to the medial epicondyle. The site where the ulnar nerve penetrates through the intermuscular septum can contribute to the compression and should be fully released. Our 2 patients had a positive Tinel sign over the FCU but not right behind the medial epicondyle. Suspicion of an anteriorly located ulnar nerve should be raised if one cannot palpate the ulnar nerve in the ulnar groove. Both our patients had a positive elbow
CASE 2 A healthy 21-year-old, right-handed woman with a history of a right both-bone midforearm fracture 8 years prior that was managed nonsurgically, was referred with an approximately 6-month history of increasing numbness and tingling in her right ring and little fingers that had failed to improve with nonsurgical treatment measures. She reported having had similar symptoms at the time of her initial injury that had resolved spontaneously. She denied subsequent trauma to the extremity. Physical examination revealed decreased sensation to light touch, temperature, and pinprick in the ulnar nerve distribution and a positive elbow flexion test. A Tinel test performed by percussing the entire course of the nerve at the elbow was noted to be positive distal to the cubital tunnel, near the origin of the FCU. Again, no palpable ulnar nerve or nerve subluxation was appreciated. X-rays showed a well-healed both-bone midforearm fracture. Electrodiagnostic studies performed at another facility were unremarkable. Despite normal electrodiagnostic testing, the patient’s symptoms and examination findings were highly suggestive of cubital tunnel syndrome. At the time of open cubital tunnel release, dissection was performed in the interval between the triceps muscle and the intermuscular septum. The ulnar groove was empty. With dissection distally, the ulnar nerve was located between the 2 heads of the FCU where it J Hand Surg Am.
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ANTERIORLY POSITIONED ULNAR NERVE
flexion test. We would have expected this to be negative given the anterior location of the nerve. However, one possible explanation is that further tightening with elbow flexion increased compression at the site where the ulnar nerve penetrated the intermuscular septum. Awareness of this rare anatomical variant is beneficial for elbow surgeons. Although there have been no reported cases of ulnar nerve injury related to this particular anatomical anomaly during elbow arthroscopy, if unrecognized, such patients could be at increased risk of injury to the aberrant ulnar nerve during placement of the superomedial portal. Knowledge of the possible anterior location of the nerve could also be of clinical importance to those performing
J Hand Surg Am.
electrodiagnostic and ultrasonographic testing in the upper extremity. Difficulty visualizing the ulnar nerve on ultrasound in the region of the cubital tunnel should prompt examination of the area anterior to the medial epicondyle to ensure that anterior positioning is not present. REFERENCES 1. Mondelli M, Giannini F, Ballerini M, Ginanneschi F, Martorelli E. Incidence of ulnar neuropathy at the elbow in the province of Siena (Italy). J Neurol Sci. 2005;234(1e2):5e10. 2. Aziz MA. Anatomical defects in a case of trisomy 13 with a D/D translocation. Tetrology. 1980;22(2):217e227. 3. Davis GA. Ulnar nerve volar to medial epicondyle: an anatomical variation. Case illustration. J Neurosurg. 2006;104(4):625.
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