The role of ulnar nerve transposition in ulnar nerve repair: a cadaver study

Ulnar nerve transposition at the elbow is recommended to diminish nerve gaps during neurorrhaphy. We undertook a cadaver study to determine the gap distance that can be overcome by subcutaneous transposition at the elbow, evaluating lacerations 2.0 cm distal to the medial epicondyle and 2.0 cm proximal to the wrist crease. With a 100-g load on each nerve stump, gaps that could be overcome were measured before and after transposition in different elbow and wrist positions. For the distal forearm lacerations, wrist position significantly affected nerve gap, while transposition and elbow position did not. Nerve gap was significantly reduced by approximately 11 mm with wrist flexion from 0 degrees to 45 degrees. For proximal forearm lacerations, gap distance was significantly affected by transposition and was dependent to a greater extent on the interaction between transposition and elbow position, with wrist position having no effect. A clinically relevant scenario for the proximal laceration compared the pretransposition gap with the elbow and wrist at neutral with the posttransposition gap with the elbow and wrist flexed. Posttransposition gap reduction, with elbow and wrist flexion at 45 degrees, was approximately 9 mm and was not significant. To span a gap near the elbow, we estimate that more than 45 degrees of elbow flexion is required.