An anatomic factor significant in transposition of the ulnar nerve.

Anterior subcutaneous or submuscular transposition of the ulnar nerve are recommended treatments for the cubital tunnel syndrome. Commonly encountered findings at submuscular transposition are the presence of a distinct fibrous septum within the main flexor-pronator origin, which arises from the proximal ulna and medial epicondyle and requires release to accomplish the transposition. Cadaver dissections were conducted to study the intermuscular fascial anatomy of the flexor-pronator origin. The surgical findings were confirmed. The fascial structure is the common aponeurosis between the flexor digitorum superficialis of the ring finger and the humeral head of the flexor carpi ulnaris. Failure to release this structure from the proximal ulna caused kinking and tethering of the nerve when transposition was attempted.