Lunate Dislocation

Aka: Lunate Dislocation, Transnavicular Perilunate Dislocation, Perilunate Dislocation, Isolated Lunate Dislocation, Pure Volar Lunate Dislocation

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II. Epidemiology

  1. Most common in children and young adults (with high energy injury)

III. Mechanism

  1. High energy injury (e.g. fall from height, Motor Vehicle Accident)

IV. Precautions

  1. Lunate Dislocations are initially missed in up to 25% of cases
  2. Deformities may be subtle

V. Types: Lunate Dislocation

  1. Transnavicular Perilunate Dislocation (TransScaphoid Perilunate Dislocation)
    1. Mid-Navicular Fracture
    2. Posterior displacement of distal Navicular Fracture pole and associated Carpal Bones (including Lunate)
    3. May be associated with Median Neuropathy (from Carpal Tunnel compression)
    4. Optimal treatment is with early surgical repair (poor outcome if delayed repair)
  2. Perilunate Dislocation
    1. Most common carpal dislocation (10% of all carpal dislocations)
    2. Intact navicular bone and wrist dorsally dislocates in relation to Lunate Bone (which remains in fossa)
    3. Missed injury in up to 25% of cases
  3. Isolated Lunate Dislocation (Pure Volar Lunate Dislocation)
    1. Lunate dislocates from Capitate
    2. Lunate rotates anteriorly (towards volar wrist)
    3. Wrist XRay lateral demonstrates anterior displacement, while on AP View, Lunate appears more triangular

VI. Symptoms

  1. Pain, swelling, tenderness and decreased range of motion of the affected wrist
  2. Median Nerve Paresthesias may be present

VII. Exam

  1. Trauma Exam
    1. High mechanism injury (esp. with Intoxication) is often associated with other injuries
    2. Multiple other injuries in 26% of Lunate Dislocation cases
    3. Ipsilateral upper extremity with additional injuries in 10% of cases
  2. Complete extremity exam (neurovascular, joint above and below, skin and compartments)
    1. Wrist Exam
    2. Hand Neurovascular Exam (esp. Median Nerve)
  3. Careful skin exam overlying dislocation
    1. Open dislocation occurs in 10% of cases

VIII. XRay

  1. Wrist XRay
    1. Diagnostic in most cases

IX. Procedure: Closed Reduction of Isolated Lunate Dislocation

  1. Background
    1. All Isolated Lunate Dislocations will ultimately require ORIF (due to carpal instability)
    2. However, attempt closed reduction and Splinting in Emergency Department
  2. Anesthesia
    1. Procedural Sedation or
    2. Median Nerve Block at Wrist (Regional Anesthesia of the Median Nerve)
      1. Short acting agent (e.g. Lidocaine) allows for re-assessment of Median Nerve post-reduction
  3. Technique
    1. Finger traps with 10-15 pound traction for 10-15 minutes
      1. Performed after Median Nerve Block or systemic Analgesics
      2. Maintain inline traction while finger traps are removed
    2. Reduction (under Procedural Sedation or Median Nerve Block)
      1. Patient's wrist positioned in slight flexion
      2. Place one thumb over dorsal Lunate, providing posterior counter support
      3. Place other thumb over the volar Lunate and apply anterior pressure toward dorsal wrist
      4. Closed reduction will fail if interposed joint capsule in dislocation (requires urgent ORIF)
  4. Splinting
    1. Return wrist to slightly extended or neutral position
    2. Apply Sugar-Tong splint
  5. Disposition
    1. Obtain post-reduction films
    2. Refer to orthopedics for definitive management (i.e. ORIF)
      1. Surgery at 3-5 days after stable closed reduction and Splinting, without Median Neuropathy
      2. Urgent orthopedic evaluation for persistent or recurrent dislocation, Median Neuropathy

X. Complications

  1. Median Nerve Injury
  2. Open Dislocation
  3. Delayed diagnosis (longterm Disability risk)

XI. References

  1. Kiel, Kumetz and Shannon (2019) Crit Dec Emerg Med 33(5): 14-5
  2. Mercier (1995) Practical Orthopedics, Mosby, St. Louis, p. 360-2

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