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Updated: Dec 22 2024

Lunate Dislocation (Perilunate dissociation)

Images
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https://upload.orthobullets.com/topic/6045/images/perilunatedislocation_1.jpg
https://upload.orthobullets.com/topic/6045/images/lunate dislocation.jpg
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https://upload.orthobullets.com/topic/6045/images/greater and lesser.jpg
  • Summary
    • Lunate/perilunate dislocations are high energy injuries to the wrist associated with neurological injury and poor functional outcomes.
    • Diagnosis requires careful evaluation of plain radiographs.
    • Treatment requires urgent closed versus open reduction and stabilization.
  • Epidemiology 
    • Incidence
      • rare
        • < 1 per 100,000 injuries annually 
      • commonly missed (~25%) on initial presentation
  • Etiology
    • Mechanism of injury
      • traumatic, high energy
      • occurs when wrist extended and ulnarly deviated
        • leads to intercarpal supination
    • Pathoanatomy
      • sequence of events
        • scapholunate ligament disrupted -->
        • disruption of capitolunate articulation -->
        • disruption of lunotriquetral articulation -->
        • failure of dorsal radiocarpal ligament -->
        • lunate rotates and dislocates, usually into carpal tunnel
      • dislocation can course through
        • greater arc
          • ligamentous disruptions with associated fractures of the radius, ulnar, or carpal bones
        • lesser arc
          • purely ligamentous
    • Categories
      • perilunate dislocation
        • lunate stays in position while carpus dislocates
        • 4 types
          • transcaphoid-perilunate
          • perilunate
          • transradial-styloid
          • transcaphoid-trans-capitate-perilunar
      • lunate dislocation
        • lunate forced volar or dorsal while carpus remains aligned
  • Anatomy
    • Normal wrist anatomy
    • Osseous
      • proximal row
        • scaphoid
        • lunate
        • triquetrum
        • pisiform
      • distal row
        • trapezium
        • trapezoid
        • capitate
        • hamate
    • Ligaments
      • interosseous ligaments
        • run between the carpal bones
          • scapholunate interosseous ligament
          • lunotriquetral interosseous ligament
        • major stabilizers of the proximal carpal row
      • intrinsic ligaments
        • ligaments the both originate and insert among the carpal bones
          • dorsal intrinsic ligaments
          • volar intrinsic ligaments
      • extrinsic ligaments
        • connect the forearm bones to the carpus
          • volar extrinsic carpal ligaments
          • dorsal extrinsic carpal ligaments
  • Classification
      • Mayfield Classification
      • Stage I
      • Scapholunate dissociation
      • Stage II
      • + lunocapitate disruption
      • Stage III
      • + lunotriquetral disruption, "perilunate"
      • Stage IV
      • Lunate dislocated from lunate fossa (usually volar)
      • - associated with median nerve compression
  • Presentation
    • Symptoms
      • acute wrist swelling and pain
      • median nerve symptoms may occur in ~25% of patients
  • Imaging
    • Radiographs
      • recommended views
        • PA
        • lateral
      • findings
        • PA
          • break in Gilula's arc
          • lunate and capitate overlap
          • "piece-of-pie sign"
            • triangular appearance of lunate
            • due to palmar rotation from dorsal force of carpus
        • lateral
          • loss of colinearity of radius, lunate, and capitate
          • SL angle >70 degrees
          • spilled teacup sign
    • MRI
      • usually not required for diagnosis
  • Treatment
    • Nonoperative
      • closed reduction and casting
        • indications
          • no indications when used as definitive management
        • outcomes
          • universally poor functional outcomes with non-operative management
          • recurrent dislocation is common
    • Operative
      • emergent closed reduction/splinting followed by open reduction, ligament repair, fixation, possible carpal tunnel release
        • indications
          • all acute injuries < 8 weeks old
        • outcomes
          • emergent closed reduction leads to
            • decreased risk of median nerve damage
            • decreased risk of cartilage damage
          • return to full function unlikely
          • decreased grip strength and stiffness are common
      • proximal row carpectomy
        • indications
          • chronic injury (defined as >8 weeks after initial injury)
            • not uncommon, as initial diagnosis frequently missed
      • total wrist arthrodesis
        • indications
          • chronic injuries with degenerative changes
  • Techniques
    • 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
        • follow with surgery
    • Open reduction, ligament repair and fixation +/- carpal tunnel release
      • approach (controversial)
        • dorsal approach
          • longitudinal incision centered at Lister's tubercle
          • excellent exposure of proximal carpal row and midcarpal joints
          • does not allow for carpal tunnel release
        • volar approach
          • extended carpal tunnel incision just proximal to volar wrist crease
        • combined dorsal/volar
          • pros
            • added exposure
            • easier reduction
            • access to distal scaphoid fractures
            • ability to repair volar ligaments
            • carpal tunnel decompression
          • cons
            • some believe volar ligament repair not necessary
            • increased swelling
            • potential carpal devascularization
            • difficulty regaining digital flexion and grip
      • technique
        • fix associated fractures
        • repair scapholunate ligament
          • suture anchor fixation
        • protect scapholunate ligament repair
          • controversy of k-wire versus intraosseous cerclage wiring
        • repair of lunotriquetral interosseous ligament
          • decision to repair based on surgeon preference as no studies have shown improved results
      • post-op
        • short arm thumb spica splint converted to short arm cast at first post-op visit
        • duration of casting varies, but at least 6 weeks
    • Proximal row carpectomy
      • technique
        • perform via dorsal and volar incisions if median nerve compression is present
        • volar approach allows median nerve decompression with excision of lunate
        • dorsal approach facilitates excision of the scaphoid and triquetrum
  • Complications
    • Transient ischemia of the lunate  
      • radiodense appearance of the lunate on radiograph reported in up to 12.5% of cases
      • usually identified 1-4 months post-injury
      • treatment
        • observation (benign and self-limiting)
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