The aetiology of fracture and nonunion in the hook of the hamate.

Fractures of the hook of the hamate are traditionally thought to be caused by direct trauma. A review of the anatomy and function of the hamate hook suggests that fracture is more likely as a result of a fatigue response that develops in the hook from repetitive load applied by the adjacent deep flexor tendons. Additional vascular compromise, from direct pressure of the tendons on critical local vessels, reduces blood flow leading to both mechanical and vascular effects that create pathological osseous change and weakening. These changes are likely to predispose to stress fracture and nonunion in repetitive gripping activities and are consistent with radiological findings.