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Carpometacarpal Fracture - Dislocation

synonyms: carpometacarpal dislocation, carpal metacarpal, Reverse Bennett's fracture

Carpometacarpal Fx ICD-9

  • 833.04 (dislocation carpometacarpal joint closed) 833.14 (open)
  • 814.00 (fracture carpal bone unspecified, closed), 814.10 (open)
  • 815.00 (fracture metacarpal bone unspecified, closed), 815.10 (open)

Carpometacarpal Fx Etiology / Epidemiology / Natural History

  • Relatively uncommon injury, generally high energy injuries
  • Often overlooked in settings of multiple trauma
  • Most common patterns: simultaneous dislocation of all four ulnar metacarpals and isolated fifth CMC Fx-dislocation. Dorsal dislocations are much more common than volar
  • Isolated dorsal dislocations/fracture-dislocations occur from longitudinal compressive forces strikeing the dorsum of the metacarpal head causing simultaneous flexion and longitudinal compression.
  • Neglected injuries lead to muscle imbalance/weakness, articular incongruity/arthritis

Carpometacarpal Fx Anatomy

  • Metacarpal bases are solidly fixed onto the distal carpus with stout volar, dorsal and intermetacarpal ligament attachments.
  • Small finger and ring finger articule on the hamate's two concavities with signifcantly more mobility than the middle and index fingers.

Carpometacarpal Fx Clinical Evaluation

  • Generally caused by high energy direct trauma/blow to the metacarpal head with the wrist flexed. Also can result from direct force to the palm, such as the handle bars in a motorcylce accident.
  • Swelling generally obscures the palpable deformity
  • Complete neurovascular exam indicated as digitial ischemia and neuropraxia have been reported.

Carpometacarpal Fx Xray / Diagnositc Tests

  • P/A, lateral and oblique views of the hand. Dorsal fracture-dislocations can be missed on standard views.
  • Best seen on 30° pronated lateral view.
  • CT: indicated if suspected CMC dislocation is not evident on plain films.

Carpometacarpal Fx Classification / Treatment

  • Reverse Bennett's fracture (5th CMC fracture dislocation): Open reduction via a small dorsal lazy-S incision, Avoid damage to the dorsal sensory branches of the ulnar nerve. Reduced and fix with a longitudinal Kirschner wire.
  • Isolated Dorsal or multiple dorsal CMC dislocation: CRPP. Traction in flexion with simultaneous longitudinal pressure on the dorsally displaced metacarpal base, followed by extension of the metacarpal head when length has been restored followed by longitudinal and/or oblique K-wire fixation.
  • For thumb injuries see: Bennet's Fracture, Rolando Fracture,

Carpometacarpal Fx Associated Injuries / Differential Diagnosis

Carpometacarpal Fx Complications

  • Pain
  • Traumatic arthitis
  • Weakness
  • Muscle imbalance

Carpometacarpal Fx Follow-up Care

  • Post-op: Volar plaster splint. is continued for 4 to 6 weeks, at which time the wire is removed. IP and MP joint ROM exercises.
  • 7-10 Days: Wound check, repeat xrays to ensure maintenance of reduction. Continue volar splinting. IP and MP joint ROM exercises.
  • 4-6 Weeks: Remove K-wires. Progress with ROM.
  • 3 Months: Evaluate ROM. Consider OT if motion is poor. Sport specific rehab.
  • 6 Months: Return to sport / unlimited activity.
  • 1Yr: Follow up xrays, outcome assessment.

Carpometacarpal Fx Review References

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