REIDER PART 1
55

Figurę 4-70. Assessing opposition strength.

thumb toward the little finger in the absence of oppo-nens function, the examiner should inspect the patienfs hand carefully to verify that true opposition is occur-ring. The patient is then instructed to press the tips of the two fingers together as tightly as possible. The exam-iner^łs two index fingers are then hooked around the base of the thumb and the little finger, respectively, and the examiner attempts to puli these two digits apart (Fig. 4-70). In the normal patient, the examiner should encounter considerable resistance but usually is able to

_Charter 4_Hand and Wrist 145

break the strength of opposition. The opponens muscle, located on the radial side of the first metacarpal, should feel rock hard to palpation. Inability to properly oppose the thumb owing to muscular wcakness is most com-monly the result of a carpal tunnel syndrome because the opponens pollicis is innervated by the motor median nerve. Severe basilar joint arthritis can also interfere with proper opposition, however, owing to pain or loss of joint rotation. Asking the patient to oppose the thumb to the ring finger instead of the little finger will eliminate the opponens digiti minimi.

Sensation Testing

If the median nerve is comprcsscd in the carpal tunnel, there may be altercd sensation in the median nerve distri-bution in the hand, which includes the palmar surface of the radial digits including the tips of the thumb, the index finger, the long finger, and the radial aspect of the ring finger (Fig. 4-71). This loss is usually evaluatcd by testing two-point discrimination and/or light touch with monofiliments at the volar tip of the thumb or index finger (Fig. 4-72A). Because the palmar cutaneous branch of the median nerve arises proximal to the carpal tunnel, the palmar base of the thumb is spared.

Ulnar nerve compression in Guyon’s canal may lead to altered sensation in the ulnar nerve distribution, including the little finger and the ulnar aspect of the ring finger. This is best evaluated by two-point discrimination and monofiliment tests at the volar tip of the little finger (see Fig. 4-72B).

Although the superficial sensory branch of the radial nerve supplies the radial dorsum of the hand, it is most

Figurę 4-71. Average sensory distribution in the hand. A, Dorsum. B, Palm.