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Introduction
  • Avascular necrosis of the lunate leading to abnormal carpal motion
  • Epidemiology
    • incidence
      • most common in males between 20-40 years old
    • risk factors
      • history of trauma
  • Pathophysiology
    • thought to be caused by multiple factors
      • biomechanical factors
        • ulnar negative variance
          • leads to increased radial-lunate contact stress
        • decreased radial inclination
        • repetitive trauma
      • anatomic factors
        • geometry of lunate
        • vascular supply to lunate
          • patterns of arterial blood supply have differential incidences of AVN
          • disruption of venous outflow leading to increased intraosseous pressure
  • Prognosis
    • progressive and potentially debilitating condition if unrecognized and untreated
Anatomy
  • Blood supply to lunate
    • 3 variations
      • Y-pattern
      • X-pattern
      • I-pattern
        • 31% of patients
        • postulated to be at the highest risk for avascular necrosis
Classification
 
Lichtman Classification
Stage Description Treatment Image
Stage I No visible changes on xray, changes seen on MRI Immobilization and NSAIDS
Stage II Sclerosis of lunate Joint leveling procedure (ulnar negative patients) 
Radial wedge osteotomy or STT fusion (ulnar neutral patients)
Distal radius core decompression
Revascularization procedures
Stage IIIA Lunate collapse, no scaphoid rotation Same as Stage II above
Stage IIIB Lunate collapse, fixed scaphoid rotation
Proximal row carpectomy, STT fusion, or SC fusion
Stage IV Degenerated adjacent intercarpal joints Wrist fusion, proximal row carpectomy, or limited intercarpal fusion
 
Presentation
  •  Symptoms
    • dorsal wrist pain
      • usually activity related
      • more often in dominant hand
  • Physical exam
    • inspection and palpation
      • +/- wrist swelling
      • often tender over radiocarpal joint
    • range of motion
      • decreased flexion/extension arc
      • decreased grip strength
Imaging
  •  Radiographs
    • recommended views
      • AP, lateral, oblique views of wrist
    • findings (see table above)
  • CT
    • most useful once lunate collapse has already occurred 
    • best for showing
      • extent of necrosis
      • trabecular destruction
      • lunate geometry
  • MRI
    • best for diagnosing early disease 
    • rule out ulnar impaction 
    • findings
      • decreased T1 signal intensity
      • reduced vascularity of lunate
Treatment
  • Nonoperative
    • observation, immobilization, NSAIDS
      • indications
        • initial management for Stage I disease
      • outcomes
        • a majority of these patients will undergo further degeneration and require operative management
  • Operative
    • temporary scaphotrapeziotrapezoidal pinning
      • indications
        • adolescent with radiographic evidence of Kienbock's and progressive wrist pain
    • joint leveling procedure
      • indications
        • Stage I, II, IIIA disease with ulnar negative variance
        • initial operative managment
      • technique
        • can be radial shortening osteotomy or ulnar lengthening
        • more evidence on radial shortening
    • radial wedge osteotomy
      • indications
        • Stage I, II, IIIA disease with ulnar positive or neutral variance
    • vascularized bone grafts
      • indications
        • Stage I, II, IIIA, IIIB disease
      • outcomes
        • early results promising, but long-term data lacking
        • best results in Stage III patients
    • distal radius core decompression
      • indications
        • Stage I, II, IIIA disease
      • technique
        • creates a local vascular healing response
    • partial wrist fusions
      • STT
      • capitate shortening osteotomy +/- capitohamate fusion
      • scaphocapitate
      • indications
        • Stage II disease with ulnar neutral or positive variance
        • Stage IIIA or IIIB disease
        • must address internal collapse pattern (DISI)
    • proximal row carpectomy (PRC)
      • indications
        • stage IIIB disease
        • stage IV disease
      • outcomes
        • some studies have shown superior results of STT fusion over PRC for stage IIIB disease
    • wrist fusion
      • indications
        • stage IV disease
      • technique
        • must remove arthritic part of joint
    • total wrist arthroplasty
      • indications
        • Stage IV disease
      • outcomes
        • long-term results not available
Techniques
  • Vascularized bone grafts
    • technique 
      • many options have been described including
        • transfer of pisiform
        • transfer of distal radius on a vascularized pedicle of pronator quadratus
        • transfers of branches of the first, second, or third dorsal metacarpal arteries
        • 4 + 5 extensor compartment artery (ECA)   
      • temporary pinning of the STT joint, SC joint or external fixation may be used to unload lunate after revascularization
  • Impact of surgical procedure on radiolunate contact stress 
Operative Procedure
% decrease on radiolunate contact stress
STT fusion   3%
Scaphocapitate fusion 12%
Capitohamate fusion 0%
Ulnar lengthening of 4mm 45%
Radial shortening of 4mm 45%
Capitate shortening and capitohamate fusion  66%, but 26% increase in radioscaphoid load

 

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