Anteriorly positioned ulnar nerve at the elbow: a rare anatomical event: case report.

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.