Snapping of the medial head of the triceps and recurrent dislocation of the ulnar nerve. Anatomical and dynamic factors.

We describe seventeen patients (twenty-two limbs) who had snapping (dislocation) of both the ulnar nerve and the medial head of the triceps over the medial epicondyle. Two patients (two limbs) were seen because of painless snapping, four patients (five limbs) had snapping and pain in the medial aspect of the elbow, three patients (three limbs) had symptoms related to the ulnar nerve only, and six patients (seven limbs) had snapping and symptoms related to the ulnar nerve. In addition, snapping was identified incidentally on routine screening in five asymptomatic limbs in four patients, one of whom was seen because of snapping and symptoms related to the ulnar nerve on the contralateral side. The diagnosis was confirmed with magnetic resonance imaging or computerized tomography, or both, in all but the first three patients, in whom the operative findings were confirmatory. Only six patients (seven limbs) were sufficiently symptomatic to be managed operatively. Of these six patients, five (six limbs) who had symptoms related to the ulnar nerve had lateral transposition or excision of the dislocating medial head of the triceps in addition to decompression and transposition of the ulnar nerve. Two of these patients had had persistent symptoms immediately after a previous transfer of the ulnar nerve performed at another institution for symptoms related to, and well documented dislocation of, the ulnar nerve; we performed the index procedure to correct the postoperative snapping, which was the result of an unrecognized dislocation of the medial head of the triceps in one patient and the result of an accessory triceps tendon in the other. One patient who had pain in the medial part of the elbow, snapping (without symptoms related to the ulnar nerve), and cubitus varus had a valgus osteotomy of the distal aspect of the humerus that corrected the line of pull of the triceps and relieved the snapping. All of the patients who were managed operatively had an excellent result (no snapping, no symptoms related to the ulnar nerve, and a full range of motion), at an average of 4.5 years postoperatively. Non-operative treatment provided control of symptoms related to the ulnar nerve in four limbs and control of pain from the snapping in four limbs. Snapping on the medial side of the elbow, even if it is associated with symptoms related to the ulnar nerve, is not necessarily caused by dislocation of the ulnar nerve alone. Patients who have a transposition of the ulnar nerve, especially those who have dislocation of the ulnar nerve, should be examined intraoperatively with the elbow in flexion and extension so that the surgeon can be certain that the medial head of the triceps does not snap over the medial epicondyle. Failure to recognize concurrent dislocation of the ulnar nerve and the medial head of the triceps can result in persistent, symptomatic snapping after an otherwise successful transposition of the ulnar nerve.