• Epidemiology
    • dorsal dislocations most common
    • index finger most commonly involved
  • Mechanism
    • a hyperextension injury
  • Simple vs. Complex
    • simple
      • volar plate not interposed in joint
      • treated with closed reduction
    • complex
      • complex dislocations have interposition of volar plate and/or sesamoids
        • in index finger flexor tendon displaces ulnarly and lumbrical displaces radially which tighten around metacarpal neck preventing reduction
        • in small finger flexor tendons and lumbrical displace radially and the abductor digiti minimi and flexor digiti minimi ulnarly preventing closed reduction
      • may require open reduction
  • Kaplan's lesion (rare) 
    • most common in index finger
    • complex dorsal dislocation of finger, irreducible
    • metacarpal head buttonholes into palm (volarly)
    • volar plate is interposed between base of proximal phalanx and metacarpal head
  • Physical exam
    • skin dimpling often seen in complex dislocations but absent in simple dislocations
  • Radiographs 
    • lateral view best shows dislocation 
    • joint space widening may indicate interposition of volar plate 
    • useful to detect associated chip fractures
  • Nonoperative
    • closed reduction
      • indications
        • simple dislocations
      • technique
        • reduction technique involve applying direct pressure over proximal phalanx while the wrist is held in flexion to take tension off the intrinsic and extrinsic flexors
        • avoid longitudinal traction and hyperextension during closed reduction, may pull volar plate into joint
  • Operative
    • open reduction
      • indications
        • complex dislocations
Surgical Techniques
  • Open reduction
    • approach
      • dorsal approach
        • split extensor tendon to expose joint
        • may be able to push volar plate out with freer elevator
        • usually need to split volar plate to remove from joint
        • use this approach for volar dislocations
      • volar approach 
        • places neurovascular structures at risk
        • release A1 pulley to expose volar plate

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