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http://upload.orthobullets.com/topic/6045/images/47a_moved.jpg
http://upload.orthobullets.com/topic/6045/images/perilunatedislocation_1.jpg
http://upload.orthobullets.com/topic/6045/images/lunate dislocation.jpg
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http://upload.orthobullets.com/topic/6045/images/greater and lesser.jpg
Introduction
  • High energy injury with poor functional outcomes
  • Commonly missed (~25%) on initial presentation
  • 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
  • Mechanism
    • 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
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
      • most common in Mayfield stage IV where the lunate dislocates into the carpal tunnel
Imaging
  • Radiographs
    • required views
      • PA/lateral wrist radiographs
    • findings
      • AP 
        • break in Gilula's arc
        • lunate and capitate overlap
        • lunate appears triangular "piece-of-pie sign"
      • lateral
        • loss of colinearity of radius, lunate, and capitate
        • SL angle >70 degrees
  • 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
 

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