The hamate (unciform) is one of the eight carpal bones found in the hand. It is the most medial bone of the proximal row, articulating with the triquetral and lunate proximally, the capitate laterally and the ring and little metacarpals distally.
The hamate (triangular refers to triquetral and 4th and 5th metacarpals to ring and little metacarpals)
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The hamate is wedge-shaped, with a curved hook of hamate (hamulus) projecting from the distal part of the palmar surface. The hook is concave laterally and its tip points laterally, enabling it to contribute to the medial wall of the carpal tunnel. There is a slight transverse groove on the distal base of the hook.
The hamate itself has a rough palmar surface and rough dorsal surface. The larger distal surface is divided into two facets by a slight ridge, the small lateral facet articulating with the base of the ring metacarpal and the medial facet with the little metacarpal. The smaller proximal surface (the base of the wedge) has a thin facet which articulates with the lunate in adduction. The medial surface is convex proximally and concave distally, and articulates with the triquetral for most of its length. The lateral surface is the articular surface with the capitate.
- The flexor retinaculum attaches to the tip of the hook
- The dorsal and palmar ligaments of the distal row attach to the dorsal and palmar surfaces respectively
- The intercarpal ligament with the capitate attaches to the lateral surface
- Articulates with the lunate at the midcarpal joint
- Articulates with the triquetral at the midcarpal joint
- Articulates with the capitate at an intercarpal joint
- Articulates with the ring metacarpal at the carpometacarpal joint
- Articulates with the little metacarpal at the carpometacarpal joint
The deep terminal branch of the ulnar nerve may run in the groove at the base of the hook
The hamate begins to ossify in the third month.
The groove for the deep terminal branch of the ulnar nerve is variably present.
The articular facet with lunate may not be present.
- May be fractured.