A 17-year-old boy presented to the emergency department with pain in his left wrist. The onset of symptoms occurred while at bat in the second game of a four-game tournament in which he was playing that day. The pain impaired his ability to bat through the remaining games. He complained of mild tingling in his small finger. He was right handed. Exam showed mild point tenderness in the proximal hypothenar region of his left hand. He had normal wrist and finger range of motion and normal finger neurovascular function. A radiograph of the wrist was interpreted by the emergency physician (and later by the radiologist) as normal. A CAT scan of the wrist was ordered.
Dx: Fracture of the Hook of the Hamate
The CAT scan shows a lucency where the small projection, or hook, comes off of the volar aspect of the hamate bone.
Hamate fractures, including hook of the hamate (or hammulus) fractures, constitute 1.5% of all carpal bone fractures. These injuries are known to occur as stress fractures after longstanding use, as with golf clubs, or acutely, with use of a bat or racquet held in the hand, or fall on an outstretched hand (1). The patient may present immediately after the injury, or, at times, the symptoms are minimal, weeks or months after the injury (by which time, nonunion of the fracture may be present) (2). The patient may complain of ill-defined pain in the ulnar half of the wrist. On exam, there may be tenderness on deep palpation in the proximal ulnar palm while pressure is applied to the dorsal ulnar aspect of the wrist. Lateral movement or flexion of the small finger increases discomfort, especially with ulnar deviation of the wrist. Initial standard wrist radiographs may be negative. When the diagnosis is considered, a carpal tunnel view and supine oblique views of the wrist may show the fracture. If the diagnosis is suspected, but radiographs are negative, a CT of the wrist should be done. One study showed that conventional radiographs had a sensitivity of 72% and a specificity of 88%, while CT had a sensitivity of 100% and specificity of 94%; hence use of CT should always be considered in case of doubt. Other considerations presenting with this clinical picture include bony contusion, fracture of the body (as opposed to the hook) of the hamate, 4th and 5th carpometacarpal injuries, ligament avulsion of the hook of the hamate or of the trapezoid ridge,(3) and damage to the triangular fibrocartilage complex.
The hook of the hamate forms the distolateral border of Guyon’s canal, through which both the ulnar artery and nerve pass; thus, this injury can result in both neurological and vascular complications (though textbooks and articles don’t discuss the complication rate or how long after the injury these complications occur); it may also result in tendon rupture (4). Immediate treatment consists of splinting and referral to a hand surgeon. Definitive treatment consists of casting for up to six weeks, internal fixation or excision of the fragment, in all cases followed by physical therapy (5).
REFERENCES
1. Harano K, Inoue G. Classification and treatment of hamate fractures, Hand Surg 2005;10(2-3)151-7
2. Gaebler C and McQueen M in Rockwood and Green’s Fractures in Adults, Lippincott, Williams, and Wilkins, Philadelphia, PA:2005, p. 886
3. Amadio P and Moran S in Green’s Operative Hand Surgery, Elsevier, Philadelphia, PA:2005 p.764
4. Boulas HJ, Milek MA. Hook of the hamate fractures, diagnosis, treatment and complications, Orthop Rev. Jun 1990;19(6)518-29
5. Scheufler O, Andresen R, Radmer S, et al. Hook of hamate fractures: critical evaluation of different therapeutic procedures. Plast Reconstr Surg Feb 2005;115(2)488-97
Rauvan Averick is an attending emergency physician at Staten Island University Hospital and an assistant professor of emergency medicine at SUNY-Downstate Medical Center.
