Pisiform

Study entry

Parts

Small pea-shaped bone on the palmar surface of the triquetrum; it is a sesamoid bone in the tendon of the flexor carpi ulnaris.

Joints

Only with the triquetrum.

Palpation

At the base of the hypothenar eminence, on the medial side of the distal wrist crease.

Clinical

Landmark of the ulnar canal: the ulnar artery and nerve pass just lateral to it.

Source: cap. 3, «Huesos de la mano»

Clinical correlation

Ulnar canal syndrome (Guyon's canal) and handlebar neuropathy

At the wrist, the ulnar nerve may be compressed between the pisiform and the hook of the hamate, in an osteofibrous canal closed by the pisohamate ligament (Guyon's canal). It causes loss of sensation in the little finger and part of the ring finger and weakness of the intrinsic muscles of the hand. There may be clawing of the 4th and 5th fingers, but, unlike a high ulnar lesion, finger flexion continues and the hand does not deviate to the radial side.

Related clinical cases

• Ulnar canal syndrome (Guyon's canal) and handlebar neuropathy

Other structures in this region

• Clavicle
• Scapula
• Humerus
• Radius
• Ulna
• Scaphoid
• Lunate
• Triquetrum