Guyon’s canal, also less frequently known as ulnar tunnel or canal, is a fibro-osseous tunnel extending from the transverse carpal ligament at the proximal aspect of the pisiform to the origin of the hypothenar muscles at the hook of hamate. It is approximately 4 cm in length.
- roof: palmar carpal ligament, palmaris brevis muscle and hypothenar connective tissue
- floor: transverse carpal ligament, pisohamate ligament, pisometacarpal ligament, flexor digitorum profundus tendons, and abductor digiti minimi muscle
- lateral wall: hook of hamate, transverse carpal ligament, flexor tendons
- medial wall: pisiform bone, flexor carpi ulnaris tendon, abductor digiti minimi muscle
- ulnar nerve: bifurcates within the canal into the deep (more radial) and superficial (more ulnar) branches
- ulnar artery and ulnar vein
- veins associated with the ulnar nerve
At the level of the hook of hamate, the canal bifurcates into two channels: the first channel contains the superficial ulnar nerve and ulnar artery, and the second channel contains the deep ulnar nerve. These are separated by either the fibrous arch of the flexor digiti minimi brevis, or the muscle itself attaching to the hook of hamate.
The abductor digiti minimi muscle can occasionally have an anomalous presence in Guyon’s canal. It was present in 25% of a sampled population and can cause compression leading to Guyon's canal syndrome .
History and etymology
Described and named by Jean Casimir Felix Guyon (1831-1920), a French anatomist and urologist in 1861 .