Cubital Tunnel Syndrome

The video demonstrates Froment's sign on the patient's right hand, which is characterized by interphalangeal (IP) flexion during attempted key pinch, and is found in patients with ulnar neuropathy. Therefore it can be found with ulnar nerve compression in the cubital tunnel (Cubital Tunnel Syndrome) or in Guyon's Canal (Ulnar Tunnel Syndrome).

Froment's sign is performed by having the patient pinch a piece of paper with the thumb IP joint extended against resistance (pulling paper away). It should be done with both hands side by side to compare them to each other.

In a hand with a ulnar neuropathy, adductor pollicis (ulnar n.) is deficient, and can not flex the MCP joint to give pinch strength with an extended IP joint. The thumb compensates by recruiting the FPL (median n.) to flex the IP joint to give pinch strength. The result is, in a positive Froment's sign, the IP joint will flex (buckle) to try to give increased strength to the pinch.

Illustration V shows a demonstration of the Froment's sign.

The ulnar nerve passes posterior to the medial epicondyle and medial to the olecranon, then enters the cubital tunnel. The roof of the cubital tunnel is primarily made up of Osborne's ligament, and the floor consists of the medial collateral ligament.

These soft tissue structures can cause narrowing of the tunnel, especially with elbow flexion, leading to ulnar nerve compression and cubital tunnel syndrome. This is shown in Illustration A. The Arcade of Struthers is a band of deep fascia that attaches to the intermuscular septum and covers the ulnar nerve 8 cm proximal to the medial epicondyle. The intramuscular septum is continuous from the medial epicondyle to the coracobrachialis muscle. The ulnar nerve travels through the two heads of the FCU distal to the cubital tunnel. These anatomic landmarks are shown in Illustration B.

Morrey evaluated 26 patients with post-traumatic contracture of the elbow who were treated with either operative release alone, or operative release and distraction arthroplasty. Twenty-four (96%) of the patients had improved elbow function and two had persistent ulnar neuritis treated with nerve transposition.

Cheung et al discuss the various surgical approaches to the elbow and the indications for each.

Video V is an educational lecture that discusses common nerve entrapment diagnosis and managment.

There are five sites of potential ulnar nerve entrapment around the elbow: arcade of Struthers, medial intermuscular septum, medial epicondyle, cubital tunnel, and deep flexor pronator aponeurosis.

The ulnar nerve emerges from the medial intermuscular septum, under the arcade of Struthers, and lies on the medial head of the triceps. At the level of the elbow, the ulnar nerve continues distally toward the posterior aspect of the condylar groove, passing between the medial epicondyle and olecranon to enter the cubital tunnel. The roof is formed by the arcuate (Osborne’s) ligament. This ligament blends distally with the antebrachial fascia superficial to the aponeurosis and connects the ulnar and humeral heads of the FCU. The ligament of Struthers is a fibrous band extending from the supracondylar process of the humerus to the medial epicondyle which can cause compression of the median nerve.

Elhassan et al discuss the pathogenesis, evaluation, and treatment of entrapment neuropathy of the ulnar nerve.

Illustration A shows the various site of compression at the elbow. Illustration V shows a submuscular ulnar nerve transposition performed Dr. Susan E. Mackinnon

The patient's clinical presentation and physical exam are consistent with cubital tunnel syndrome. The clinical photograph demonstrates Froment's sign; compensatory IP hyperflexion of FPL (AIN) to compensate for the loss of adductor pollicis (ulnar nerve) during key pinch. Simple decompression of the ulnar nerve is less invasive and achieves clinical outcomes equivalent to decompression with transposition.

Zlowodzki et al conducted a meta-analysis evaluating anterior transposition and simple decompression of the ulnar nerve. No difference in motor nerve-conduction velocities or clinical outcome scores was found.

Bartels performed a prospective randomized trial (included in the Zlowodski meta-analysis) on 152 patients comparing simple decompression to transposition. No difference in clinical results at 1 year were reported, but a significantly higher complication rate occurred in the transposition group (31%) compared to simple decompression (9.6%).

Nabhan et al performed a level 1 study randomizing 66 patients to simple decompression or subcutaneous ulnar nerve transposition. No differences were found with respect to clinical outcome or nerve conduction velocities.

Illustration V is an educational presentation discussing ulnar nerve transposition at the elbow.