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Lunate Dislocation

Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist
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Rx Musculoskeletal System (A - Z)
Lunate dislocation is an uncommon but serious wrist injury, often resulting from a high-energy mechanism of trauma. Individuals with lunate dislocations typically present after a high impact falls onto an extended wrist. Commonly reported symptoms include wrist pain, swelling, and decreased sensation and/or paresthesia in the median nerve distribution secondary to carpal tunnel injury. Lunate dislocations typically occur due to a fall on an outstretched hand (or during a motor vehicle injury) where there is forceful dorsiflexion of the wrist. There is an injury to all of the perilunate ligaments, most significantly the dorsal radiolunate ligament.
The treatment choices for perilunate and lunate dislocations are closed reduction and casting, open reduction-internal fixation-ligament repair, trapeziolunate external fixation, limited wrist arthrodesis, and proximal row corpectomy.
If the knuckle of the third metacarpal head is level with the knuckles of the second and fourth metacarpal heads, the sign is positive and indicative of a lunate dislocation. The patient should rest the involved forearm on the table. Then, ask the patient to extend the thumb so that these tendons become prominent.

Background

  • Uncommon wrist injury secondary to trauma
  • The Lunate is disarticulated and displaced volar (dorsal dislocation less common) from both the capitate and the radius.
  • The remainder of the carpal bones remain in normal anatomic position in relation to the radius
  • Frequently missed on initial presentation due to subtlety of radiographs

Pathophysiology

  • Classically a fall on an outstretched hand causes wrist hyperextension, ulnar deviation, and intercarpal supination.
  • The sequence of events:
    • Scapholunate disruption
    • Disruption of capitulating articulation
    • Disruption of lunotriquetral articulation and Lunotriquetral Ligament
    • Failure of dorsal radiocarpal ligament
    • Lunate rotates and dislocates, usually into the carpal tunnel
  • Epidemiology
    • Carpal dislocations account for less than 10% of all wrist injuries

Differential Diagnosis

  • Fractures
    • Distal Radius Fracture
      • Barton’s Fracture
      • Chauffer’s Fracture
      • Colles’ Fracture
      • Die-Punch Fracture
      • Radial Styloid Fracture
      • Smith’s Fracture
    • Distal Ulna Fracture
    • Carpal Fractures
      • Scaphoid Fracture
      • Lunate Fracture
      • Triquetrum Fracture
      • Pisiform Fracture
      • Trapezium Fracture
      • Trapezoid Fracture
      • Capitate Fracture
      • Hamate Fracture
    • Essex Lopresti Fracture
  • Dislocations
    • Carpometacarpal Joint Dislocation
    • Distal Radioulnar Joint Dislocation
    • Lunate Dislocation
    • Perilunate Dislocation
  • Instability & Degenerative
    • Scapholunate Instability
    • Lunotriquetral Instability
    • Scaphoid Nonunion Advanced Collapse
    • Distal Radial Ulnar Joint Instability
    • Kienbocks Disease
  • Tendinopathies & Ligaments
    • De Quervain’s Tenosynovitis
    • Intersection Syndrome
    • TFCC Injury
    • Wrist Tendinopathies
    • Extensor Carpi Ulnaris Instability
  • Neuropathies
    • Carpal Tunnel Syndrome
    • Pronator Teres Syndrome
    • Anterior Interosseus Nerve Syndrome
    • Posterior Interosseus Nerve Syndrome
    • Guyon Canal Syndrome
  • Pediatric Considerations
    • Distal Radial Epiphysitis (Gymnast’s Wrist)
    • Torus Fracture
  • Arthropathies
    • Wrist Osteoarthritis
    • Rheumatoid Arthritis
  • Cartilage
    • Osteochondral Defect
  • Vascular
    • Hypothenar Hammer Syndrome
  • Other
    • Ganglion Cyst of Wrist
    • Ulnar Impingement Syndrome
    • Infectious Tenosynovitis

Diagnosis

  • General: Physical Exam Wrist
  • Often pain and swelling over the dorsum of the wrist
  • Limited range of motion of the wrist
  • Median nerve distribution may be diminished due to volar displacement of the lunate
  • It May have associated radial styloid, scaphoid, capitate, or triquetral avulsions and dislocations

Radiographs

  • Standard Radiographs Wrist
  • The piece of pie sign is the characteristic triangular appearance of the lunate on the PA view caused by volar rotation of the lunate
  • Spilled teacup sign is found on the lateral x-ray due to volar rotation of the lunate

MRI

  • Not required to make a diagnosis may be helpful to clarify soft tissue injuries

Classification

Mayfield Classification

  • Stage 1: scapholunate dissociation
  • Stage 2: scapholunate dissociation, lunocapitate disruption
  • Stage 3: scapholunate dissociation, lunocapitate disruption, lunotriquetral disruption
  • Stage 4: Lunate dislocated with median nerve compression

Treatment

Nonoperative

  • Most cases require surgical management for optimal outcomes

Acute Management

  • Emergent Orthopedic consultation for reduction and stabilization with operative management
  • Immediate closed reduction and splinting alone may be utilized though often associated with poor functional outcomes and redislocation
  • Closed reduction technique
    • Finger traps, elbow at 90 degrees of flexion
    • Hand 5-10 lbs traction for 15 minutes
    • Dorsal dislocations are reduced through wrist extension, traction, and flexion of wrist
    • Apply Sugar Tong Splint

Operative

  • Generally requires surgical management

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