American Society for Peripheral Nerve

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Congenital Anterior Transposition of the Ulnar Nerve at the Elbow: A Rare Anatomic Variant
Ellen Satteson, MD; Zhongyu Li, MD
Department of Orthopaedic Surgery, Wake Forest Baptist Medical Center, Winston-Salem, NC

Introduction: Cubital tunnel syndrome is the second most common compressive neuropathy of the upper extremity. Anatomic variants of the ulnar nerve at the elbow are rare.

Methods: Two cases of congenital transposition of the ulnar nerve, identified intra-operatively during cubital tunnel release, are presented here. One, a 66-year-old male who presented with typical cubital tunnel symptoms with no history or upper extremity trauma or surgery. The other, a 22-year-old female with cubital tunnel symptoms and a history of a both bone forearm fracture as a child.

Results: In these cases, the ulnar nerve was identified behind and penetrated through the intermuscular septum about 3-5 cm proximal to the medial epicondyle at the elbow. It then ran anterior to the pronator-flexor mass before entering the forearm between the ulnar and humeral heads of the flexor carpi ulnaris.

Discussion: Although a rare anatomic anomaly, congenital anterior transposition of the ulnar nerve is potentially under reported and has great clinical importance. In individuals with cubital tunnel syndrome, diagnosis and surgical treatment may be negatively impacted if the electrodiagnostic and ultrasound technician or surgeon fails to recognize the aberrant anatomy. Upper extremity surgeons should also be mindful of this condition when performing elbow arthroscopy or medial epicondyle release to prevent inadvertent injury to the nerve.

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