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Chapter 4 Hand and Wrist 153

Figurę 4-85. A and B, Midcarpal instability test (arrows indicate tlie direction of the applied compression force).

ward with the right hand and upward with the left hand. In the normal patient, very little movemcnt or discomfort is noted. If significantly morę translation is noted than in the opposite wrist, Iunotriquetral instability should be suspected. If this maneuver reproduces the patients pain or results in a grinding sensation, this is further evidence that Iunotriquctral instability is responsible for the patient s symptoms.

Midcarpal instability is the most difficult of the wrist instabilitics to detect and interpret. When midcarpal instability is present, the proximal and distal rows of carpal bones do not move synchronously in relation to each other as the wrist progresses from radial to ulnar deviation. Instead, a jump, a catch, or a clunk is felt in the middlc of the joint motion. For the midcarpal instability test, the patient is positioned with the elbow flexed and forearm pronated. To test the patient s right wrist, for example, the examiner^łs right hand grasps the patients right hand and the examiners left hand grasps the patient’s right forearm. The cxaminer places the patient’s wrist in a position of ulnar deviation and loads the patient s wrist by pushing the hand proximally toward the forearm (Fig. 4-85A). While maintaining this loading, the patients wrist is slowly moved into radial deviation (Fig. 4-85B). In the normal wrist, this movement should pro-cecd smoothly, accompanied by no significant jumping, catching, or clunking sensations. If midcarpal instability is present, the examiner usually sees and/or feels the midcarpal joint jump, catch, or clunk as the wrist moves into radial deviation. Pushing upward on the volar surface of the pisiform should correct the subluxation and cause the clunk to disappear.

Distal Radioulnar Joint. Instability can also exist in the distal radioulnar joint. Most commonly, the head of the ulna subluxes dorsally in relation to the radius when the forearm is in the pronated position. The test for instability in the distal radioulnar joint is sometimes callcd the piano key test. To perform it, the patient is placed in a position of elbow flexion and forearm pronation. To test the right wrist, for example, the examincr grasps the patients ulnar head between the thumb and the indcx finger of his or her own left hand and the distal radius between the thumb and the index finger of his or her own right hand. The examiner then translates the distal ulna up and down in relation to the distal radius (Fig. 4-86). The examiner compares the amount of translation with the patients other wrist and notes whether clicking, popping, or pain is produced. The finding of inereased translation, compared with the opposite wrist, accompanied by clicking, popping, or pain suggests the prescnce of symptomatic instability of the distal radioulnar joint. The examiner can also stress the distal radioulnar joint by compressing the distal ulna against the distal radius with one hand while pas-sively pronating and supinating the patient s forearm with the other hand (Fig. 4-87). If this maneuver produces pain, popping, or grinding at the distal radioulnar joint,

Figurę 4-86. Piano key test of the distal radioulnar joint.