Pisiform !
The pisiform is the small pea-shaped wrist bone felt at the base of the palm on the little-finger side; it sits inside a wrist tendon.
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What it is
A pea-sized bone in the flexor carpi ulnaris tendon, felt at the heel of the hand.
What it does
One of the eight carpal bones that let the wrist bend and carry load to the forearm.
Key facts
- Joints with
- Triquetrum only
- Landmarks
- Sesamoid in the FCU tendon; medial wall of Guyon's canal
Relations
- Behind
- Triquetrum, at the pisotriquetral joint
- Above
- Flexor carpi ulnaris tendon, which ends in it
- Below
- Pisiform ligaments to the hook of the hamate and the base of the 5th metacarpal; origin of the abductor digiti minimi
- Lateral
- Guyon's canal with the ulnar nerve and ulnar artery, then the hook of the hamate
- In front
- Palmaris brevis and skin of the hypothenar eminence
How to find it
The easiest carpal bone to feel: a pea-sized knob at the base of the hypothenar eminence, on the distal wrist crease on the little-finger side. With the wrist relaxed in slight flexion it can be moved from side to side, and the flexor carpi ulnaris tendon is followed down to it.
Examination
- Pisotriquetral grind: pressing and rolling the pisiform against the triquetrum reproduces pain in pisotriquetral arthritis or instability
On imaging
Overlaps the triquetrum on the PA view; it is seen clear of other bones on a lateral view in slight supination or on a carpal tunnel view.
Clinical notes
- Ulnar nerve compression in Guyon's canal (for example in cyclists leaning on handlebars) weakens the intrinsic hand muscles, with or without numbness of the little finger
- A fall on the hypothenar eminence can fracture it; painful nonunion or arthritis may be treated by removing it
- Landmark for an ulnar nerve block at the wrist: just proximal to it, the nerve lies under the radial edge of the flexor carpi ulnaris tendon, with the ulnar artery on its radial side
Development
The last carpal bone to ossify, around age 9–12, sometimes from more than one centre, which can mimic a fracture.
Test yourself
Think of the answer, then tap the question to see it.
In which tendon is the pisiform a sesamoid bone?
The flexor carpi ulnaris tendon, which continues as the pisohamate and pisometacarpal ligaments.
Which canal do the pisiform and the hook of the hamate bound, and what passes through it?
Guyon's canal, through which the ulnar nerve and ulnar artery enter the hand.
Which is the last carpal bone to ossify?
The pisiform, around age 9–12, sometimes from more than one centre, which can mimic a fracture.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- os pisiforme TA2 1254
- Official Spanish (DeCS)
- Hueso pisiforme
- English (TA2)
- Pisiform
Related
- Abductor digiti minimi
- FCU tendon
- Flexor carpi ulnaris
- Flexor retinaculum
- Pisiform ligaments
- Wrist capsule
- Wrist collateral ligaments
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Hand Carpal Bones.
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Representative model, for educational purposes only.
