Pisohamate ligament

At a glance

English

Pisohamate ligament

Latin (TA2)

Ligamentum pisohamatum

System

Ligament

Region

Hand

Side

Paired, left and right

About the pisohamate ligament

The pisohamate ligament lies on the palmar side of the wrist at the base of the little finger side of the hand. It runs from the pisiform, the small pea-shaped bone sitting on the front of the triquetrum, downwards and outwards to the hamate's hook, the curved projection that juts forward from the hamate into the palm. Both points can be felt through the skin at the heel of the hand.

The pisiform is a sesamoid bone within the tendon of flexor carpi ulnaris. That tendon does not stop at the pisiform; its pull is carried on beyond it by two ligaments. The pisohamate ligament takes it on to the hamate's hook, and the pisometacarpal ligament takes it to the base of the fifth metacarpal. These two bands are therefore best regarded as continuations of the tendon, and they allow flexor carpi ulnaris to act on the hand as well as the wrist. The ligament also gives part of the origin of abductor digiti minimi, the muscle that moves the little finger away from the others.

Its most important relation is with the ulnar canal, also called Guyon's canal, a short tunnel at the wrist between the pisiform and the hook of the hamate. The pisohamate ligament, together with the flexor retinaculum, forms its floor, and the palmar carpal ligament forms its roof. The ulnar nerve and its companion artery pass through this canal into the hand, superficial to the carpal tunnel rather than within it. At the distal end of the canal the nerve divides into its superficial and deep branches, the deep branch curving round the hamate's hook.

Compression of the ulnar nerve in the canal, for instance from long cycling on dropped handlebars, from a fracture of the hook of the hamate or from a ganglion, causes numbness of the little finger and weakness of the small hand muscles.

Attachments and function

Attaches from

The pisiform, as a continuation of the tendon of flexor carpi ulnaris.

Attaches to

The hook of the hamate.

Function

Carries the pull of flexor carpi ulnaris on to the hamate, gives part of the origin of abductor digiti minimi and helps to floor the ulnar canal.

Nerve supply

Articular twigs of the ulnar nerve.

Blood supply

Branches of the ulnar artery.