Iatrogenic Snapping of the Medial Head of the Triceps After Ulnar Nerve Transposition

Robert J. Spinner, MD, Gerard T. Gabel, MD


J South Orthop Assoc. 2001;10(4) 

In This Article

Abstract and Introduction

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.

Snapping of a portion of the medial head of the triceps is a condition in which a portion of the distal triceps dislocates over the medial epicondyle with elbow flexion or with extension from a flexed position.[1,2,3,4,5,6,7,8] It has been ascribed to anatomic variations in the medial head of the triceps muscle or triceps tendon or the bony anatomy of the elbow (eg, cubitus varus, hypoplastic trochlea or medial epicondyle, and medially elongated olecranon).[9] These variations may be congenital, developmental, or acquired (posttraumatic). Small changes in the triceps position or size, which may be manifested by dynamic motion (such as exercises that involve active elbow extension against resistance), can also result in snapping.[10,11]

Snapping triceps is frequently associated with ulnar nerve dislocation. Because many physicians are not familiar with snapping triceps, it is commonly misdiagnosed as the more common clinical entity of isolated ulnar nerve dislocation; in these patients, unrecognized snapping due to the triceps may persist after ulnar nerve transposition for ulnar nerve dislocation and neuropathy.[12] Some authors have raised the possibility that snapping triceps may occur secondarily either by releasing the cubital tunnel[5] or by resecting the medial intermuscular septum (MIS).[7] However, in both of these reports, the ulnar nerves dislocated preoperatively and the possibility of a coexisting dislocating triceps could not be eliminated definitively.

In the following case, one of us (G.T.G.) carefully documented that no dislocating structure was present with flexion/extension of the elbow preoperatively and intraoperatively (before ulnar nerve transposition), but the triceps dislocated post- operatively. We believe this case is important in establishing medial triceps instability as a possible complication of ulnar nerve transposition.