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Figure 9a. Cubital tunnel. (a) Drawing of the medial aspect of the elbow shows the course of the ulnar nerve (dark gray region) in the cubital tunnel. At the condylar groove, the nerve passes between the medial epicondyle and the olecranon, just deep to the cubital tunnel retinaculum and the arcuate ligament (light gray region) between the humeral and ulnar origins (*) of the flexor carpi ulnaris muscle (FCU). (b, c) Transverse 5-12-MHz US scans of the proximal tunnel (b) and distal tunnel (c) show the normal relationship of the ulnar nerve (arrow) to the medial epicondyle (ME) and the two heads of the flexor carpi ulnaris muscle (*). O = olecranon.