Name of bone
The hamate bone (unciform bone) in the wrist is readily distinguished by its wedge-shaped form and the hook-like process that projects from its volar surface. It is situated at the medial and lower angle of the carpus, with its base directed downward, resting on the fourth and fifth metacarpal bones, and its apex directed upward and lateralward.
The etymology derives from the Latin hamatus "hooked," from hamus which means "hook."
Muscle and ligament attachments
- The superior surface, the apex of the wedge, is narrow, convex, smooth; it articulates with the lunate.
- The inferior surface articulates with the fourth and fifth metacarpal bones by concave facets that are separated by a ridge.
- The dorsal surface is triangular and rough for ligamentous attachment.
- The volar surface presents a curved, hook-like process - the hamulus - at its lower and ulnar side. It is directed forward and lateralward.
- The medial surface articulates with the triangular bone by an oblong facet, cut obliquely from above, downward and medialward.
- The lateral surface articulates with the capitate by its upper and posterior part, the remaining portion being rough for the attachment of ligaments.
Figure 1. Surface anatomy of the left hamate
This is the bone most commonly fractured when an amateur golfer hits the ground hard with his/her golf club on his/her downswing. The fracture is usually a hairline fracture, commonly missed on normal radiographs. Symptoms include pain aggravated by gripping, tenderness over the hamate, and symptoms of irritation of the ulnar nerve, such as numbness and weakness of the pinky finger with partial involvement of the ring finger as well, the "ulnar 1 1/2 fingers."
Hamate fracture is also a common injury in baseball players. A number of professional baseball players have had the bone removed during the course of their careers.
The calcification of the hamate bone is seen on radiographs during puberty and is sometimes used in orthodontics to determine if the adolescent patient is suitable for orthognathic intervention (eg. before or at their growth spurt).