Pisiform
Os pisiforme
Also known as: pea-shaped bone
A small pea-shaped sesamoid bone in the tendon of flexor carpi ulnaris, lying on the palmar surface of the triquetrum. It is the last carpal bone to ossify.
Overview
The pisiform articulates only with the triquetrum. It develops within the tendon of flexor carpi ulnaris, which continues beyond it as the pisohamate and pisometacarpal ligaments to the hook of hamate and base of the 5th metacarpal. It is easily palpated at the base of the hypothenar eminence, at the distal wrist crease. It gives attachment to the flexor retinaculum, abductor digiti minimi and the palmar carpal ligament, and forms the medial wall of Guyon’s canal (ulnar canal), through which the ulnar nerve and artery pass into the hand.
- Location
Palmar surface of the triquetrum, medial wrist (base of the hypothenar eminence).
Anatomy
- Articulations
Triquetrum (pisotriquetral joint).
- Ossification
Last carpal to ossify, ≈9–12 years.
Function
- Increases the lever arm of flexor carpi ulnaris
- Attachment for the flexor retinaculum and abductor digiti minimi
- Landmark for the ulnar nerve and artery at the wrist
Clinical significance
Guyon’s canal (ulnar tunnel) syndrome
Compression of the ulnar nerve between pisiform and hook of hamate (cyclists’ handlebar palsy, ganglia, hamate fractures) causes hypothenar and interosseous weakness with ulnar-sided numbness, sparing the dorsal ulnar hand (dorsal cutaneous branch arises proximally).
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.