Hamate
Os hamatum
Also known as: unciform bone, hook of hamate
A wedge-shaped bone on the ulnar side of the distal carpal row with a prominent hook (hamulus) projecting into the palm, which bounds both the carpal tunnel and Guyon’s canal.
Overview
The hamate articulates with the 4th and 5th metacarpals distally, the capitate laterally, the triquetrum proximally and medially, and sometimes the lunate. The hook of hamate curves anteriorly from its palmar surface and gives attachment to the flexor retinaculum, the pisohamate ligament and the hypothenar muscles flexor digiti minimi and opponens digiti minimi. The hook forms the medial wall of the carpal tunnel and the lateral wall of Guyon’s canal, and the deep branch of the ulnar nerve curves around its base. The hook can be palpated ≈2 cm distal and lateral to the pisiform.
- Location
Medial (ulnar) end of the distal carpal row.
Parts & subdivisions
- BodyArticulates with metacarpals 4 and 5.
- Hook (hamulus)Flexor retinaculum and hypothenar attachments; bounds the carpal tunnel and Guyon’s canal.
Anatomy
- Articulations
Capitate, triquetrum, lunate (variably), 4th and 5th metacarpals.
- Ossification
Single centre ≈2–4 months (second carpal to appear).
Function
- Supports the mobile 4th and 5th metacarpals
- Anchors the flexor retinaculum and hypothenar muscles
- Pulley for the flexor tendons of the little and ring fingers
Clinical significance
Fracture of the hook of hamate
Occurs in golfers, baseball batters and racquet players when the handle strikes the hypothenar eminence; poorly seen on standard X-rays (carpal tunnel view or CT). May injure the ulnar nerve or cause flexor tendon rupture.
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.