Fracture, Hamate: Hook, Body

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Fracture, Hamate: Hook, Body
Mark Stovak
A fracture through the hook or the body of the hamate
Hamate fractures occur in 3 patterns:
  • Type 1: Hook
  • Type 2a: Coronal (dorsal oblique and splitting)
  • Type 2b: Transverse (1)
  • Hook fracture:
    • Hook of the hamate fractures account for <2% of all carpal bone fractures (2).
    • The number of hook of the hamate fractures reported in the literature is low because routine x-rays usually are normal, and symptoms are nonspecific (2).
    • Average length of time from injury to correct diagnosis is 10 mos (3).
    • Fractures most commonly occur at the base of the hook (1).
  • Body fracture: Body of the hamate fractures is rare and much less common than hook fractures.
Risk Factors
Hook fracture: Sporting activities that involve a bat, club, or racket (2)
General Prevention
Avoid holding the handle end of the bat, club, or stick in the palm to prevent it from creating pressure on the hook of the hamate.
  • Acute traumatic injury
  • Repetitive stress leads to a stress fracture.
  • Hook fracture:
    • Type 1
    • Hook of the hamate fractures occurs in athletes who use equipment with a handle (eg, golf clubs, baseball bats, and rackets) (2).
    • Athlete grips the handle of the club, bat, or racket over the distal ulnar aspect of the palm, placing the handle in close proximity to the hook of the hamate (2).
    • In golf, the fracture often occurs when the club head accidentally strikes too much ground and a large divot is taken. In baseball, most fractures occur at the end of forceful check swings as opposed to swings that make contact with the ball (2).
    • A less common mechanism of injury is a fall on an outstretched hand (2).
    • Stress fractures are also possible of the hook and are likely if no traumatic event can be identified in the history.
  • Body fracture:
    • Body fractures often result from punching a hard stationary object, such as a wall, with a closed fist (type 2a). The 4th and 5th metacarpals are driven back into the hamate, leading to a fracture. Body fractures may accompany a boxer's fracture (1).
    • They also may occur when the hamate is smashed between two objects in a dorsopalmar fashion (type 2b) (1).
  • Stress fractures have been described from repetitive military-style knuckle push-ups (4).
Physical Exam
  • Point tenderness occurs in the palm over the hook of the hamate. The hook is located by projecting a line from the pisiform to the center of the head of the index metacarpal. Rarely, if the fracture is at the base of the hook, pain may be greater over the dorsal hamate than over the hook in the palm (because the hamate is covered on the volar aspect with thick skin, subcutaneous fibrofatty tissue, and parts of the palmaris brevis muscle and transverse carpal ligament, making palpation difficult) (2).
  • Painful and weak grasp (2)
  • Check pulses: An Allen test will help to rule out ulnar artery thrombosis (2).
  • Signs of partial or complete 4th/5th flexor digitorum profundus (FDP) tendon rupture may be present. Pain with grip, decreased grip strength, crepitance with 4th/5th finger motion, and eventually, loss of active flexion at the 4th/5th finger distal interphalangeal joints may indicate FDP injury; a small percentage of all hook fractures are correctly diagnosed only after FDP tendon rupture (2).
  • Decreased sensation or weakness may be due to ulnar or median nerve injury. The fracture fragments may injure the nerves directly, or swelling and inflammation may injure them indirectly (2).
Diagnostic Tests & Interpretation
  • Hook fracture:
    • The routine wrist series (anteroposterior [AP], lateral, and oblique views) usually are negative, often delaying diagnosis (2).
    • Ring of the hook can be visualized on AP view; if it is not present, this may be a clue to a hook fracture (5).
    • Carpal tunnel view often will aid in making the diagnosis. However, to obtain this view, the wrist must be forcefully hyperextended. During the acute phase of the injury, pain and limited range of motion may not allow proper positioning to make this x-ray possible (2).
    • Another useful view is the radially deviated thumb-abducted lateral view (the hook is seen in profile between the 1st and 2nd metacarpals) (6).
    • An additional view is the hamate hook lateral view. This view places the film on a 30-degree slant board and rests the hand on the film with the thumb abducted and the beam perpendicular to the table (the hook is seen in profile between the 1st and 2nd metacarpals) (7).
    • CT scanning is the gold standard for diagnosis but often is unnecessary if plain films show the fracture. CT scans are useful if plain films are negative and a fracture is highly suspected. CT scanning has the advantage of visualizing both hamates at the same time and can be used to evaluate the extremely rare case of a bipartite hamate, which usually is bilateral and is a normal variant. CT scan is performed with both hands in the praying position (palm to palm) (2).
  • Body fracture:
    • The routine wrist series (AP, lateral, and oblique views) is more useful for diagnosis of body fractures than for hook fractures. The oblique and lateral views are the most useful. However, many fractures are still missed by plain films (1,8,9).
    • CT scan may be needed to delineate further the exact fracture pattern and degree of fragment displacement. CT scan should be considered when routine films are negative but a fracture is highly suspected (1,8,9).
Differential Diagnosis
  • Flexor/extensor carpi ulnaris tendon injury
  • Metacarpal/carpal bone fracture or contusion
  • Ulnocarpal ligament sprain
  • Triangular fibrocartilaginous complex tear
  • Ulnar artery thrombosis
  • Ulnar nerve entrapment/neuropathy
  • Carpal tunnel syndrome
Ongoing Care
  • Prognosis of hook fractures is generally good if they are diagnosed and treated (cast, excision, ORIF) early before tendon injury/rupture occurs (13).
  • Prognosis for hamate body fractures is generally good if they are diagnosed and treated (cast, ORIF, closed reduction and pinned) early enough to maintain congruent joint surfaces (8,9).
  • 814.08 Closed fracture of hamate (unciform) bone of wrist
  • 814.18 Open fracture of hamate (unciform) bone of wrist

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