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Chronic Capitolunate Instability

- Discussion: (see: dynamic instability);
    - capitolunate joint has high potential for instability, since it is mainly stabilized only by the radiocapitate ligament (and captiotriquetral ligament, to a lesser degree); (see wrist ligaments);
    - may result from malreduced radial styloid frx, or any condition which shortens or reduces tension in the ligament;
    - often results from severe dorsiflexion injury;
    - patients may note wrist clicking and pain while lifting heavy objects;
    - grasping in supination may provoke symptoms;
    - diff dx:
      - prior to making this diagnosis, need to r/o:
            - Kienbock's, scapholunate diastatsis, capitate frx, lunotriquetral diastasis;
            - no VISI or DISI deformity should be present;

- Radiographs:
    - lateral view of wrist;
    - dorsal capitate displacement apprehension test;
          - w/ patient's hand kept in a neutral position (w/ regard to flexion and extension as well as supination and pronation), the surgeon places his thumb under the capitate and attempts to force it dorsally;
                  - flouroscopy will confirm any dynamic instability;
          - also consider taking a contralateral radiograph of the normal wrist

Chronic capitolunate instability

Central Carpal Instability - Capitate Lunate Instability Pattern.  Diagnosis by Dynamic Displacement. Lousi DS, et al. Orthopedics. 1984;7(11):1693-1696.