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Scapholunate Advanced Collapse (SLAC)

- Discussion:
    - scapholunate advanced collapse (SLAC) refers to a specific pattern of osteoarthritis and subluxation which results from untreated chronic scapholunate dissociation or from chronic scaphoid non-union;
    - degenerative changes occur most often in areas of abnormal loading;
           - radial-scaphoid joint is involved initially, followed by degeneration in the unstable lunatocapitate joint, as capitate subluxates dorsally on lunate;

- Radiographs:
    - radioscaphoid joint is first to develop degenerative changes;
    - capitolunate & STT joints, follow in order w/ degenerative changes;
    - capitate migrates proximally into space created by scapholunate dissociation;
    - radiolunate joint is usually spared because of concentric articulation of lunate w/ in speroid lunate fossa of distal radius;
    - lunate:
            - w/ end stage SLAC midcarpal joint collapses under compression & lunate assuming an extended or dorsiflexed position (DISI deformity);

- Treatment:
    - proximal row carpectomy:
           - advantages are that it is technically easy, and often allows better preservation of strength and motion, as compared to limited carpal arthrodesis;
                  - patients can expect over 60% of normal ROM as compared to opposite wrist and over 90% of normal grip strength;
                  - this compares to four corner fusion, in which patients can expect less than 50% ROM and about 75% grip strength;
           - relatively contra-indicated w/ capitolunate arthrosis;
    - wrist fusion
    - limited carpal fusion: (LCF);
           - 4 corner fusion:
           - involves preservation of radiolunate joint and stabilization of the midcarpal row;
           - usually LCF is combined w/ scaphoid excision inorder to adress radioscaphoid arthrosis;
           - incomplete reduction of the dorsiflexed lunate may result in limitation of wrist extension;
           - may be indicated for wrists w/ more extensive intercarpal arthrosis;

- Outcomes:
    - in the report by Cohen MS, et al, 2 cohort populations of 19 patients from separate institutions performing exclusively either a scaphoid excision and 4-corner arthrodesis (lunate, capitate, hamate, and triquetrum) or proximal row carpectomy (PRC) for scapholunate advanced collapse arthritis were compared.
            - length of the follow-up period averaged 28 months for the 4-corner arthrodesis group compared with 19 months for the PRC patients;
            - at the follow-up examination wrist motion revealed no significant differences in the flexion-extension arc, averaging 81° in the PRC patients and 80° following 4-corner arthrodesis, which was 62% and 58%, respectively, of the opposite wrist.                
            - 4-corner arthrodesis patients maintained greater radial deviation and total percent radial-ulnar deviation of the wrist;
            - grip strength averaged 71% for the PRC group compared with 79% for the 4-corner arthrodesis patients.
            - pain relief was similar using a variety of measures and patient satisfaction was equivalent.
            - both PRC and scaphoid excision and 4-corner arthrodesis are motion-preserving options for the treatment of scapholunate advanced collapse arthritis with minimal subjective or objective differences in short-term follow-up evaluations.
            - ref: Degenerative arthritis of the wrist: proximal row carpectomy versus scaphoid excision and four-corner arthrodesis 

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Scapholunate advanced collapse wrist: proximal row carpectomy or limited wrist arthrodesis with scaphoid excision.

Motion preserving procedures in the treatment of scapholunate advanced collapse wrist: proximal row carpectomy versus four corner arthrodesis.