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Non Dissociative Carpal Instability

- See: carpal instability

- Discussion:
    - refers to a proximal row instability which occurs in the absence of instability between the individual proximal carpi;
           - ie, the scapholunate and lunotriquetral intervals are normal;
    - potential sites of pathology:
           - capitolunate instability
                    - palmar subluxation of the capitate on the lunate, which occurs as a consequence of palmar translation of proximal row on the radius;
           - STT instability:
           - ulnar mid-carpal instability;
           - distal radial malunion;
    - exam:
           - in a majority of patients, there is a painful clunk as the wrist moves from radial to ulnar deviation (causing the lunate to move from a flexed to an extended position);
    - radiographs:
           - palmar translation of the carpi on the radius may often show VISI deformity;
           - less often dorsal translation of the carpi may produce a DISI deformity;
           - arthrograms are usually negative;
    - non operative treatment:
           - ulnar gutter splint w/ a pisiform boost;
           - only 40% of patients w/ mid carpal instability will remain satisfied with non operative treatment;
    - operative treatment:
           - radial shortening procedure:
                  - w/ negative ulnar variance (and steep radial inclination), consider a radial shortening procedure (w/ possible closing wedge osteotomy), and a possible ligament reconstructive procedure;
                  - the radial shortening osteotomy may improve the sliding dynamics of the proximal carpi and may prevent the "clunk" which is characteristic of midcarpal instability;
                  - in well selected patients, a radial shortening procedure will yeild good results in over 80% of patients;
           - stabilization of dorsal triquetro-hamate joint:
                  - indicated for ulnar-midcarpal instability;
           - mid-carpal fusion:
                  - indicated for fixed or static deformities

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