Fig. 1. Cross-sectional views of the ulnar nerve ultrasonographic tracing in normal control. The ulnar nerve is shown within the dotted line. (A) Wrist at the Guyon canal level. Arrowheads show the flexor retinaculum. (B) Midforearm, where the nerve splits from the ulnar artery. (C) Cubital tunnel inlet at the medial epicondyle. The Osborne ligament is partially visualized (arrowheads). C, capitate bone; FCU, flexor carpi ulnaris; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; ME, medial epicondyle; O, olecranon; P, pisiform bone; S, scaphoid bone; U, ulnar bone; UA, ulnar artery.