The ulnar nerve is surrounded by the tendon expansion of the flexor carpi ulnaris muscle at the wrist: an anatomical study of Guyon's canal.

Abstract

The ulnar tunnel (Guyon's canal) is an osseofibrous tunnel for the ulnar nerve and artery. With regard to the proximal palmar wall (palmar carpal ligament) of the ulnar tunnel, detailed anatomical data such as attachment sites, fibrous continuity to surroundings, and variations have not been clearly described. In this study, topology of Guyon's canal was examined, especially to the palmar side of the ulnar nerve, focusing on the continuity of tendinous structures to reveal a more detailed constitution of Guyon's canal. The palmar wall of Guyon's canal was investigated in 113 forearms of 57 cadavers. The dorsal wall of the canal was also investigated in 25 subjects. The ulnar nerve passed lateral to the pisiform and the flexor carpi ulnaris tendon. At the level of the pisiform, except for one, the ulnar nerve passed dorsal to the aponeurosis expanding from the flexor carpi ulnaris tendon and the periosteum of the pisiform, and this aponeurosis laterally merged with the palmar aspect of the flexor retinaculum. Moreover, the ulnar nerve ran palmar to the pisohamate ligament and the flexor retinaculum extended from the same tendon. The present study suggests that the aponeurosis of palmar side to the ulnar nerve connected with the flexor carpi ulnaris tendon, the periosteum of the pisiform, and the palmar surface of the flexor retinaculum. These findings indicate that the ulnar nerve is surrounded by the aponeurotic portion expanding from the flexor carpi ulnaris tendon at the wrist, which is a new insight of Guyon's canal.