Charter 4 Hand and Wrist 141
pollicis longus. Rcsistance testing of these motions, there-fore, adds little information to the rest of the examina-tion. However, strength of ulnar and radial deviation can be tested, if desired, with the patients elbow flexed and the forearm pronated. The patient is asked to make a fist. To test the strength of ulnar deviation, the patient is instructed to ulnar-deviate the wrist and resist the exam-iners attcmpts to force it back into radial deviation (Fig. 4-60). Conversely, to test the strength of radial deviation, the patient is asked to radial-deviate the wrist and resist the examiners attempt to force it back into ulnar devia-tion (Fig. 4-61).
ABDUCTORS AND ADDUCTORS OF THE FlNGERS
Abduction of the fingers is powered by the dorsal interos-seiy whereas adduction is powered by the volar (palmar) interossei. Ali of these muscles are innervated by the ulnar nerve. To test the strength of abduction, the patient is positioned with the elbows flexed and the forearms pronated. Usually both hands are tested simultaneously for ease of comparison. The patient is instructed to abduct the fingers as far as possible and to maintain that position whilc the examiner attempts to force the fingers back together with his or her own fingers (Fig. 4-62). The examiner should be able to overcome the strength of the abductors with a feeling of moderate resistance. The first dorsal interosseous is by far the largest and most visible of the interossei. If the examiner is uncertain as to whether weakness of the interossei is present, it may be helpful to test the first dorsal interosseous in isolation. This is done with the patienfs hand in the same basie position. The patient is instructed to abduct the index finger and to maintain it in that position while the exam-
Figurę 4-61. Assessing radial deviation strength.
iner attempts to push it back into adduction (Fig. 4-63). The examiner may palpate the first dorsal interosseous with the index finger of his or her free hand.
The volar interossei are responsible for adduction of the fingers, a relatively weak action. Finger adduction strength may be tested by asking the patient to sąueeze a file card or piece of paper between the adducted fingers. The patient is then instructed to sąueeze the fingers together as tightly as possible in an attempt to prevent the examiner from withdrawing the card (Fig. 4-64). The examiner should sense moderate resistance as the card is withdrawn.
Figure 4-60. Assessing ulnar dcviation strength.
MOVEMENTS OF THE THUMB
Thumb extension is powered by the extensor pollicis longus and extensor pollicis brevis, both of which are innervated by the posterior interosseous branch of the
Figurę 4-62. Assessing finger abduction strength.