CUBITAL TUNNEL SYNDROME
Cubital tunnel syndrome is the most common peripheral nerve compression syndrome after carpal tunnel syndrome and involves compression of the ulnar nerve at or around the elbow. The cubital tunnel is a fascial sheath that the ulnar nerve runs through just posterior to the medial epicondyle. Nerve compression can occur through the tunnel or at sites just proximal or distal to it, such as the medial intermuscular septum, the arcade of Struthers, the flexor carpi ulnaris fascia, and the deep flexor-pronator aponeurosis. A subluxating ulnar nerve may also produce symptoms similar to those of nerve compression. Other causes of ulnar nerve symptoms around the elbow can include adhesions from prior surgery; presence of an anomalous muscle (anconeus epitrochlearis); tumors; snapping of the medial triceps; bony changes from arthritis, prior fractures, or heterotopic bone; and anatomic deformities, such as cubitus valgus and cubitus varus. The arcade of Struthers is an aponeurotic band located approximately 8 cm proximal to the medial epicondyle that runs from the medial head of the triceps to the medial intermuscular septum. As the ulnar nerve crosses from the anterior to the posterior compartment in the distal part of the upper arm, it can pass underneath this band, if present. The arcade can particularly become a point of entrapment if the ulnar nerve is transposed anteriorly and the band is not released.
|CUBITAL TUNNEL SYNDROME: SITES OF COMPRESSION|
Symptoms of cubital tunnel syndrome include medial-sided elbow pain and paresthesias in the ulnar side of the palm and ulnar one and a half digits of the hand. A positive Tinel sign will re-create these paresthesias by tapping along the course of the ulnar nerve on the medial side of the elbow. The location of the Tinel sign may help to localize the exact site of nerve compression. Direct pressure can exacerbate symptoms by increasing compression of the nerve in the cubital tunnel, whereas elbow flexion can cause traction-related deformation of the nerve that increases symptoms. Elbow flexion can also demonstrate evidence of nerve instability, because the ulnar nerve will typically dislocate or subluxate anterior to the medial epicondyle with elbow flexion and cause a snapping or clicking sensation. Snapping of the medial triceps can also create a clicking sensation at the elbow with range of motion and must be distinguished. With more chronic or severe cases of entrapment, motor findings can be present, including weakness and wasting of the intrinsic muscles of the hand. When symptoms of cubital tunnel syndrome are present, an electromyographic study of the extremity can be performed both to confirm that the abnormality is localized to the elbow and to determine the severity of the neuropathy. Ulnar nerve compression can occur proximally at the cervical spine or brachial plexus, as well as distally in the forearm, wrist, or hand, although much less commonly.
Nonoperative management is the initial treatment in milder cases of cubital tunnel syndrome and consists of activity modification and splinting to take pressure off the nerve, such as avoidance of repetitive or prolonged elbow flexion and use of splints that keep the elbow in a relatively extended position, particularly at night. Elbow pads can also be worn during the day to prevent compression on the nerve. Surgery is indicated when nonoperative measures fail and involves in-situ decompression of the ulnar nerve or ulnar nerve transposition. In-situ decompression is often used in milder cases, whereas transposition is performed in severe cases and in situations in which nerve instability is present. When performing an ulnar nerve transposition, all possible sites of nerve entrapment proximal and distal to the cubital tunnel should be decompressed, in addition to releasing the cubital tunnel. This includes release of the arcade of Struthers if present, excision of the medial intermuscular septum, and release of the flexor carpi ulnaris and flexor digitorum superficialis fascia. Ulnar nerve transposition can be subcutaneous or submuscular and acts to decompress the nerve by placing it in a position anterior to the medial epicondyle. Subcutaneous transposition is more commonly performed, and in this technique the nerve is stabilized anteriorly by a loose fasciodermal sling. Submuscular transposition is considered in cases of revision surgery and in patients with little to no subcutaneous fat. The flexor-pronator origin is detached with this technique to allow placement of the ulnar nerve anteriorly and adjacent to the median nerve. The flexor-pronat r origin is then repaired over the transposed nerve.
|Submuscular transposition of ulnar nerve|