Lunate Dislocations ( perilunate dissocation)- wrist instability Flashcards Preview

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Flashcards in Lunate Dislocations ( perilunate dissocation)- wrist instability Deck (23):

How does this injury occur?

  • High energy injury when wrist EXTENDED and ULNARLY deviated -> intercarpal supination


Does this injury have good functional outcomes

No they are poor


What are the type of disslocation?

  • Perilunate dislocation- lunate stays in position while carpus dislocates
    • Transcaphoid-perilunate
    • Perilunate
    • Transradial-styloid
    • Transscaphoid-trans-capitate-perilunar
  • Lunate dislocation-( see pic) lunate forced volar/dorsal whilst carpus remains alligned


What is the pathoanatomy?

  • 1) Scapholunate ligament disrupted
  • 2) Capitolunate articulation disrupted
  • 3) Lunotriqetral articulation disrupted
  • 4) Failure of dorsal radiocarpal ligament  
  • then lunate rotates and dislocates


Where can the dislocation occur?

  • Thru greater arc- ligamentous and fracture
  •  Lesser arc- just ligamentous


what bones are in the proximal row?

  • scaphoid
  • lunate
  • triquetrum
  • pisiform


what bones are in the distal row?

  • trapezium
  • trapezoid
  • capitate
  • hamate


What are the major stabilisers of the proximal row?

  • scapholunate ligament
  • lunotriquetral ligament


What are the intrinsics ligaments?

  • Dorsal and volar intrinsic ligaments


What are the extrinsics ligaments in the hand?

  • volar extrinsic
  • dorsal extrinsic


Name the classification system for perilunate dislocation ?



Can you describe the MAYFIELD classification?

  • stage 1- scapholunate dissociation
  • stage 2- + capitolunate dissociation
  • Stage 3 - + lunotriquetral disruption, perilunate(seepic)
  • Stage 4- + lunate DISLOCATED from lunate fossa usually volar- 


What is stage 4 associated with ?

MEDIAN N compression


What do you see on X-rays?


  • Break in GILULA's arc ( see pic)
  • lunate and capitate overlap
  • lunate appears triangular piece of pie sign


  • loss of colinearity of radius, lunate and capitate
  • Scapholunate angle >70 degrees


How do you tx perilunate dislocation?


Closed reduction and casting but lead to poor functional outcomes so reduce the surgery!!


  • EMERGENCY CLOSED REDUCTION /SPLINTING + open reduction, ligament repair fixation and possible carpal tunnel release=  all acute injuries <8 wks
  • oc- reduced median nerve damage/ cartilage damage
  • Return to full function unlikely, reduced grip strength and stiffness common


What are the indications for closed/open reduction , fracture fixation, ligament repair and splinting?

A injury <8 weeks old


What other tx are available?

  • Proximal row carpectomy- for chronic injury >8 weeks, not uncommon as injury often initally missed
  •  Total wrist arthrodesis- chronic injury with degenerative changes


What surgical approach would you use to open and reduce the lunate?


  • Dorsal - longitudinal centred over listers tubercle
  • excellent exposure of prox row and mid carpal joints but can't do carpal tunnel thru this
  • Volar- extended carpal tunnel incision just prox to volar wrist crease
  • Both dorsal and volar approach- adv: added exposure, easier reduction, access distal scaphoid fracture, ability to repair volar ligaments and carpal tunnel decompression
  • dis= some believe volar lig no need for repair, increase swelling, potential carpal devascularisation, difficult regaining digital flexion grip


What is the principles of surgical tx?

  • Fix fractures
  • Repair SL lig- suture anchor protect SL lig repair- K wire vs circulage wire
  • Repair Lunotriquetral ligament


What would you do post op?

  • Short arm thumb spica cast
  • convert to short arm cast at first post op visits
  • cast at least 6 weeks


What is the principles of prix row carpectomy tx?

  • Preform volar and dorsal incisions
  • if median n compression is present volar approach allows median N decompression and excision of lunate
  • dorsal approach facilities excision of scaphoid and triquetrum


Describe how you would preform a close reduction of the lunate?

  • Finger traps, elbow at 90 degrees
  • hand 5-10 ILbs for 15 mins
  • dorsal disolocations reduced thru wrist Extension, traction and flexion of the wrist
  • Apply split
  • Follow with surgery


How are the unusual dorsal dislocations reduced?

  • Wrist extension, traction and flexion apply a long splint and follow up with surgery