Ulnar canal

The ulnar canal (a.k.a. Guyon's canal) is a fibro-osseous tunnel located at the anteromedial aspect of the wrist. It serves as a crucial passageway for the ulnar nerve and ulnar artery into the hand.

Boundaries

• Roof: Primarily formed by the palmar carpal ligament, a superficial thickening of the antebrachial fascia.

• Floor: Composed of the flexor retinaculum (transverse carpal ligament) and the hypothenar muscles

• Medial (ulnar) wall: Defined by the pisiform bone

• Lateral (radial) wall: Formed by the hook of the hamate.

Contents

The canal transmits the ulnar nerve (which typically divides into superficial sensory and deep motor branches within the canal) and the ulnar artery.

Relationship with the carpal tunnel

The palmar carpal ligament creates the superficial roof of Guyon's canal. The flexor retinaculum, forming the deeper floor of Guyon's canal, simultaneously serves as the roof of the adjacent carpal tunnel, which houses the median nerve and flexor tendons. Thus, the ulnar nerve and artery pass superficial to the flexor retinaculum but deep to the palmar carpal ligament as they enter the hand.