ABSTRACT
Cubital tunnel syndrome is the second most common nerve entrapment neuropathy of the upper extremity after carpal tunnel syndrome. Five possible locations of nerve entrapment include the arcade of Struthers, medial intermuscular septum, medial epicondyle, cubital tunnel itself with the arcade of Osborne, and deep flexor pronator aponeurosis. In addition to compression of the ulnar nerve at these locations, traction-related deformation of the ulnar nerve during elbow flexion is also thought to be a causative factor. This deformation results in increased intraneural pressure, whereas the cross-sectional areas of the cubital tunnel and the ulnar nerve at the elbow decrease (1). Ulnar nerve strain is greatest with maximum elbow flexion directly behind the medial epicondyle (2). In the normal cubital tunnel, the ulnar nerve strain that occurs with elbow flexion does not cause any symptoms or signs, whereas in the pathologic condition, symptoms and signs of ulnar neuropathy occur with elbow flexion. Another source of nerve compression occurs at the posterior bundle of the medial collateral ligament (PMCL), which forms the floor of the cubital tunnel. The posterior bundle tightens in elbow flexion and thus compresses the ulnar nerve (3).
