Guyon’s Canal

canalis ulnaris (Guyoni)

Guyon's canal (ulnar tunnel) is the fibro-osseous tunnel at the wrist through which the ulnar nerve and artery pass from the forearm into the hand. It is bounded medially by the pisiform, laterally by the hook of hamate, roofed by the palmar carpal ligament and palmaris brevis, and floored by the flexor retinaculum and pisohamate ligament.

Region: Forearm

Clinical Relevance

Clinical Notes

Ulnar nerve compression in Guyon's canal (ulnar tunnel syndrome) produces hypothenar weakness and little/ring finger numbness. Three zones within the canal determine the pattern: zone 1 (proximal to bifurcation — motor + sensory), zone 2 (around deep motor branch — pure motor), zone 3 (superficial sensory branch — pure sensory). Ganglion cysts, hook of hamate fractures, and anomalous muscles are common causes. EMG precisely localises the level of compression within the canal.

Pathology

Common Injuries & Conditions

Ulnar Tunnel Syndrome

Ulnar nerve compression in Guyon's canal producing hypothenar weakness, ring and little finger numbness, and a positive Tinel sign at the wrist, with the zone of compression determining the motor-sensory pattern, treated by canal decompression.

Hook of Hamate Fracture

Fracture of the hamate hook from a direct blow (golf club, bat) compressing the ulnar nerve in Guyon's canal, producing ulnar-sided hand pain and ring/little finger neuropathy, diagnosed by CT and treated by fragment excision.