Hook of Hamate Fracture

Figure 1: Frontal radiograph of the right wrist shows no apparent fracture. In retrospect, there may be slight indistinctness of the "eye" of the hamate hook.
Figure 2: Axial CT image at the level of the hamate shows a nondisplace fracture near the base of the hamate hook (arrow).

Facts:

• Uncommon fracture that is easily missed on radiography
• Hook of hamate fracture is more common than fracture of the hamate body
• Direct blow to the hook, or avulsion of transverse carpal ligament and pisohamate ligament
• Presenting with pain on ulnar side of the palm aggravated by grasp, point tenderness over the hook at 1 cm distal and radial to the pisiform
• Best seen on carpal tunnel view (radiography) or CT
• If displaced and untreated, avascular necrosis and nonunion may occur.

Imaging Features

• On frontal radiograph, there is absence or indistinctness of the "eye" of hamate (oval, dense cortical ring shadow over the hamate)
• On CT scan, the fracture line is apparent at the hook best seen on axial images. It can involve the tip or the base of the hook

Reference:

Singh AK, Kaewlai R. Extremity Trauma. In: Soto and Lucey's Emergency Radiology the Requisites, 2008.