Hamate fractures mainly occur in two locations - the hook of the hamate or the body. Hook of the hamate fractures are common in sports with hand held equipment where a direct blow occurs to the palm of the hand - for instance a baseball bat, golf club or tennis racquet striking the palm over the hook. Fractures of the hamate body are less common and can be associated with 5th or sometimes 4th metacarpal fractures.
The hamate is the most ulnar carpal bone on the distal row. The blood supply to the hamate is variable with 70% have only vascular supply to the body predisposing hook fractures to non-union. Anatomical variants of incomplete fusion of the hook of the hamate to the body (os hamulus proprius) may be confused with non-union. Attachments to the hamate include the transverse carpal ligament and flexor carpi ulnaris.
Patients will present with ulnar sided wrist pain and point tenderness over the hook of the hamate. Possible associated symptoms are flexor tendinopathies including attritional rupture and ulnar neuropathy. These fractures can often present late when the pain of the acute injury is ignored and the pain is chronic not subsiding. In these cases non-union may already be present on initial presentation.
Standard radiographs of the wrist (AP and lateral) may be insufficient to make the diagnosis and a carpal tunnel or 45 degree supination oblique view may be required. CT is the most sensitive diagnostic study. When in doubt of hook fractures versus os hamulus proprius an MRI may distinguish the acuity of the injury.
Acute injuries can be treated closed with cast immobilization. Hook of the hamate non-unions can be excised with small fragments or fixed with bone graft and screws when fragments are large enough. Displaced hamate body fractures may either be precutaneously pinned or fixed with an open reduction.
Non-union may occur with vascular disruption. Ulnar neuropathy may have profound affects. Flexor tendon rupture over the bony prominence is not an uncommon complication.