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Exam for Scapholunate Instability

- See:
      - Carpal Instability:
              - scapholunate advanced collapse
              - scapholunate instability  

- Discussion:
    - scapholunate and lunate injuries cause tenderness just distal to Lister's tubercle;
           - marked prominence of the entire carpus dorsally may indicate of a perilunate dislocation;
    - SLD is characterized by limited range of motion and increased weakness;
    - Watson test:
           - this test provokes dorsal subluxation of the proximal scaphoid over the dorsal rim of the radius, as the wrist is radially deviated;
           - is performed by grasping the patient's hand from its ulnar aspect of the small metacarpal with the examiner's thumb on the palmar surface of the distal pole of the scaphoid;
                - alternatively, the patient's hand is grasped by the examiner's hand from the radial aspect of the index metacarpal with the thumb and the palmar surface;
                - it is critical for the examiner's thumb to apply pressure to the distal pole of the scaphoid, in order to prevent it from flexing;
           - move wrist from ulnar to radial deviation w/ distal tuberosity compressed;
           - as scaphoid flexes to more vertical orientation w/ radial deviation, tuberosity compression forces proximal pole subluxation dorsal to lip of radius;
           - as the examiner's thumb pressure is removed, the subluxed scaphoid reduces, and may produce a palpable clunk and dorsal wrist pain (indicating instability of the scapholunate ligament);
           - this test has been criticized for low specificity;
                 - in the study by Wolfe, et al (1997), 36% of normal individuals had a positive shift test;
                        - when examined flouroscopically, many of these individuals had a capitolunate instability;
                        - Kinematics of the scaphoid shift test.

The scaphoid shift test.

Examination of the scaphoid

Radiographic observation of the scaphoid shift test.