Cubital tunnel syndrome caused by abnormal insertion of triceps brachii muscle.

Some cases of cubital tunnel syndrome are caused by anatomical abnormalities such as the epitrochleo-anconeus muscle or snapping and bulkiness of the medial head of the triceps brachii muscle. We report a rare cause of cubital tunnel syndrome that has not been reported previously. It was caused by an abnormal insertion of the medial head of the triceps muscle into the medial epicondyle. The clinical course and operative findings are described.