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Scapho-Lunate Advanced Collapse

synonyms:SLAC wrist

SLAC ICD-9

SLAC Etiology / Epidemiology / Natural History

  • Primary disorder in the SLAC wrist is that of scapholunate dissociation secondary to scapholunate interosseous ligament rupture . Scapholunate dissociation leads to unopposed volar flexion of the scaphoid and the dorsal intercalated segmental instability (DISI) pattern
  • Scapholunate dissociation is generally from trauma, but may occur from calcium pyrophosphate deposition.
  • Most common cause of wrist arthritis. 57% of degenerative wrist arthritis (Watson HR, Ballet FL. Journal of Hand Surgery 1984;9A, No. 3 May 1984).

SLAC Anatomy

SLAC Clinical Evaluation

  • Variable degrees of wrist pain, swelling and decreased ROM. Advanced disease is associated with night pain.
  • May have remote history of wrist trauma.

SLAC Xray / Diagnositc Tests

  • Degenerative changes progress from the radial styloid and scaphoid along the scaphoradial joint.
  • Lateral radiographs may show the scapholunate angle to be increased beyond 60°, which is felt to be the upper limit of normal.  Normal scapholunate angle=47 range=30-60 degrees.
  • PA radiograph, the scaphoid appears foreshortened, has a “cortical ring” sign(volar flexed scaphoid distal pole seen in cross section) and there is a scapholunate gap of greater than 3 mm
  • PA clenched fist view in ulnar deviation accentuates widenings at the scapholunate interval
  • Carpal height Index= distance between the base of the third metacarpal and the articular surface of the radius divided by the length of the third metacarpal on a neutral P/A xrays. Normal = 0.54 +/- 0.03. Best evaluated by comparing Carpal height index to that of the normal side. (Mann Fa, Radiology 1992;184:15). Can also compare carpal height index using the height of the capitate. Normal using capitate = 1.57 +/- 0.05.

SLAC Classification / Treatment

  • Stage I=degenerative changes (narrowing/sclerosis) in scaphoid tip (narrowing and beaking).
    Treatment: scaphocapitate or scaphotrapeziotrapezoid fusion with resection of the radial styloid.
  • Stage II=degenerative changes in entire scaphoid fossa.
    Treatment: proximal row carpectomy vs scaphoid excision and lunate-capitate-hamate-triquetral (four-corner) arthrodesis
  • Stage III=degenerative changes in capitolunate joint and scaphoid fossa.
    Treatment: proximal row carpectomy vs scaphoid excision and lunate-capitate-hamate-triquetral (four-corner) arthrodesis. Arthrodesis is favored due to arthritic changes in the capitate.
  • Stage IV=degenerative changes in wrist.
    Treatment: proximal row carpectomy vs scaphoid excision and lunate-capitate-hamate-triquetral (four-corner) arthrodesis. Arthrodesis is favored due to arthritic changes in the capitate.
  • Non-operative treatment = splinting, activity modifications, NSAIDs, steriod injections.

SLAC Associated Injuries / Differential Diagnosis

SLAC Complications

  • Degenerative changes in the radiocapitate articulation.
  • Stiffness, motion loss.
  • Weakness.
  • CRPS
  • Continued pain.
  • Instability.

SLAC Follow-up Care

  • Post-op: Volar splint in neutral, elevation.
  • 7-10 Days: Wound check, short arm cast.
  • 4 Weeks: Cast removed, xray wrist. Start gentle ROM / strengthening exercises. Functional activities. Cock-up wrist splint prn / for light duty work. No heavy manual labor
  • 3 Months:Full activities, may resume manual labor if adequate strength has been achieved.
  • 6 Months:
  • 1Yr: follow-up xrays, assess outcome

SLAC Review References

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