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
- Traumatic arthitis
- 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