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Fracture, Hamate: Hook, Body

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Fracture, Hamate: Hook, Body
Mark Stovak
Basics
Description
A fracture through the hook or the body of the hamate
Epidemiology
Hamate fractures occur in 3 patterns:
  • Type 1: Hook
  • Type 2a: Coronal (dorsal oblique and splitting)
  • Type 2b: Transverse (1)
Incidence
  • 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.
Etiology
  • Acute traumatic injury
  • Repetitive stress leads to a stress fracture.
Diagnosis
History
  • 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
Imaging
  • 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
Treatment
  • Hook fracture:
    • Acute treatment (<2 wks)
      • One option is excision of the hook distal to the fracture. Most patients return to their previous level of functioning in their sport or occupation by 8 wks. Excision has been the favored approach for both displaced and nondisplaced fractures (10)[C].
      • Conservative option for nondisplaced fractures is a short-arm cast. The cast should immobilize the metacarpophalangeal joints of the 4th/5th fingers and be a thumb spica to decrease micromotion at the hook. Cast should be worn for 6–8 wks to prevent nonunion. If pain is still present after cast removal, then excision for nonunion is the treatment of choice (11)[C].
      • Decision between casting and surgery is based on the lifestyle demands of the patient. The athlete who does not want to risk having a nonunion after casting may opt for surgery to minimize the time away from sport. Similarly, a patient with a job that requires repetitive grabbing, gripping, or lifting may elect for excision to reduce the risk of an extended period of time away from work (10)[C].

      • P.201


    • Delayed treatment (>2 wks):
      • Nonunion of the hook of the hamate is very common. Nonunion is related to micromotion from the soft tissue attachments to the hook but also may be related to a tenuous blood supply similar to the scaphoid (10)[C].
      • Excision of the hook is the treatment of choice for these injuries to prevent a nonunion. The sooner the fragment is removed and the base smoothed, the less likely is the chance for tendon rupture and/or neurovascular damage (12)[C].
      • An alternative approach is open reduction and internal fixation (ORIF); the goal is to maintain maximal grip strength by preserving the pulley system for the 4th/5th FDP tendons. Although this seems logical, the loss of grip strength associated with excision has been minimal, resulting in excision being the most popular surgical treatment method (10)[C].
      • Treatment for painless nonunion is excision to reduce the risk of tendon rupture and/or neurovascular injury (2)[C].
  • Body fracture:
    • Coronal fractures are often associated with 4th and 5th metacarpal dislocations that require reduction. Once reduced, stability must be assessed. If the reduction is stable and the fracture nondisplaced, then a short-arm cast can be used for 4–6 wks. If the fracture is displaced, then ORIF or closed reduction with pinning must be used to obtain congruent joint surfaces to prevent degenerative joint disease (1)[C].
    • Transverse fractures, if not displaced, can be treated in a short-arm cast for 4–6 wks or by ORIF or closed reduction and pinning if displacement has occurred (1)[C].
Ongoing Care
Prognosis
  • 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).
Complications
  • Complete rupture of the FDP tendon is reported to occur in 15–20% of cases of nonunion. The FDP of the little finger ruptures more commonly than that of the ring finger (2)[C].
  • Excision is associated with a 3% complication rate; complications include ulnar/median nerve injury, ulnar palmar arch vessel injury, weakness, painful grip, altered sensation, flexor tendon adhesions, and scar tenderness (2)[C].
References
1. Hirano K, Inoue G. Classification and treatment of hamate fractures. Hand Surg. 2005;10:151–157.
2. Binzer T, Carter P. Hook of the hamate fracture in athletes. Op Tech Sports Med. 1996;4:242–247.
3. Murray PM, Cooney WP. Golf-induced injuries of the wrist. Clin Sports Med. 1996;15:85–109.
4. Busche MN, Knobloch K, Rosenthal H, et al. Stress fracture of the hamate body and fourth metacarpal base following military style push-ups: an unusual trauma mechanism. Knee Surg Sports Traumatol Arthrosc. 2008.
5. Boulas H, Milek M. Hook of the hamate fractures: diagnosis, treatment, and complications. Orthop Rev 1990;XIX:518–529.
6. Bhalla S, Higgs PE, Gilula LA. Utility of the radial-deviated, thumb-abducted lateral radiographic view for the diagnosis of hamate hook fractures: case report. Radiology. 1998;209:203–207.
7. Akahane M, Ono H, Sada M, et al. Fracture of hamate hook–diagnosis by the hamate hook lateral view. Hand Surg. 2000;5:131–137.
8. Chase JM, Light TR, Benson LS. Coronal fracture of the hamate body. Am J Orthop. 1997;26:568–571.
9. Ebraheim NA, Skie MC, Savolaine ER, et al. Coronal fracture of the body of the hamate. J Trauma. 1995;38:169–174.
10. Scheufler O, Andresen R, Radmer S, et al. Hook of hamate fractures: critical evaluation of different therapeutic procedures. Plast Reconstr Surg. 2005;115:488–497.
11. Carroll RE, Lakin JF. Fracture of the hook of the hamate: acute treatment. J Trauma. 1993;34:803–805.
12. David TS, Zemel NP, Mathews PV. Symptomatic, partial union of the hook of the hamate fracture in athletes. Am J Sports Med. 2003;31:106–111.
13. Bishop A, Beckenbaugh R. Fracture of the hamate hook. J Hand Surg. 1988;13A:135–139.
Codes
ICD9
  • 814.08 Closed fracture of hamate (unciform) bone of wrist
  • 814.18 Open fracture of hamate (unciform) bone of wrist
Clinical Pearls
  • The treatment option that will allow the quickest return to play with the least amount of residual symptoms is excision of the hook of the hamate.
  • Routine plain-film radiographs are not sensitive for identifying hook of the hamate fractures. A specialized view (eg, carpal tunnel; radial-deviated, thumb-abducted lateral; or hamate hook lateral) or a CT scan is usually needed for identification.
  • Surgery is recommended to prevent tendon rupture even in the absence of pain related to fracture.


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