Latrogenic snapping of the medial head of the triceps after ulnar nerve transposition.

We postulate an iatrogenic cause for snapping of the medial head of the triceps. A patient whose ulnar nerve and triceps did not dislocate over the medial epicondyle preoperatively had snapping of a portion of the medial triceps after submuscular transposition of the ulnar nerve. We believe that release of the brachial fascia and excision of the medial intermuscular septum removed the restraint to anterior translation of the medial aspect of the triceps, permitting dislocation of a portion of the medial head of the triceps with elbow flexion in this case. Previous reports of snapping of the triceps resulting after ulnar nerve transposition occurred in patients whose ulnar nerve dislocated preoperatively; in these cases, the triceps was thought to have dislocated preoperatively (along with the ulnar nerve) but was not recognized. Careful intraoperative assessment of the triceps after ulnar nerve transposition should prevent medial triceps instability as a postoperative concern.