REIDER PART 1
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156 Chapter 4_Hand and Wrist

Figurę 4-91. A and B, Assessing capillary refill.

however, return to the nailbed within 2 seconds or 3 sec-onds. If reperfusion occurs morę slowly than this, circu-lation to the finger is compromised. Examination of the other digits allows the examiner to determine whether the problem is confined to one particular finger or affects the entire hand.

Allen's Test. Alleifs test is designed to determine whether both the radial and the ulnar arteries contribute significantly to the perfusion of the hand. This Information is important to know before performing a procedurę that might injure one of the arteries, such as inserting an arterial linę into the radial artery or surgically approach-ing the scaphoid tubercle from its volar aspect.

The Allen test is performed with the patients elbow flexcd and forearm supinated. The examiner locates the radial and ulnar pulses as described in the Palpation section and places a thumb over each. The normal color of the patients fingersand palm is noted (Fig.4—92A).The patient is then instructcd to open and close the hand three times and then make a tight fist (Fig. 4-92B). This action has the effect of exsanguinating much of the blood from the patients hand. The radial and ulnar arteries are then simul-taneously compressed beneath the examiner s thumbs. The patient is then instructed to open the hand. Immediately after opening, the hand should appear blanched because the examiner is occluding inflow from both arteries (Fig. 4—92 C). The examiner then quickly releases compression from one of the arteries and observes the color of the hand (Fig. 4-92D). If the released artery is contributing significantly to perfusion, the normal color of the palm and volar fingers should return within a few seconds.

The test is then repeatcd, this time releasing the other artery while maintaining compression on the artery that was previously released. Again, the time required for perfusion to return to the hand is noted. In about 80% of normal individuals, the ulnar artery predominates over the radial artery. However, both arteries should be able to perfuse the hand in the majority of individuals. If the return of color to the palm is significantly pro-longed after the release of either artery, the examiner should conclude that perfusion from that artery is reduccd.

The Allen test can also be used for assessing the rel-ative contributions of the two digital arteries to an individual finger. In this case, the examiner observes the normal resting color of the finger in que$tion and has the patient exsanguinate it by flexing the finger tightly. The examiner then obstructs both digital arteries by compressing at both sides at the base of the finger (Fig. 4-93A). Because the digital arteries are closer to the volar than the dorsal surface of the fingers, the exam-iners thumbs should be positioned to compress from the volar surface. The patient is then instructed to extend the finger (Fig. 4-93B). The examiner then releases compression from one of the digital arteries and observes the time required for normal color to return to the finger (Fig. 4-93C). As with the Allen test of the hand, the procedurę is then repeated for the other digital artery so that the relative contributions of the two vessels can be compared.

The physical findings in common conditions of the hand and wrist are summarized in Table 4—1.