A 60-year-old man sustained a traumatic amputation through the left thumb and index metacarpal. Thumb reimplantation was attempted but failed because of inadequate venous return, leaving the defect shown at 14 days post-injury.
The blood supply to the forearm comes from the radial and ulnar arteries, which normally communicate distally through the deep and superficial palmar arches (see hand anatomy). The integrity of the connection is tested preoperatively by the Allen test, alternately compressing each artery, squeezing the blood out of the hand and releasing to observe the return of color. If the arches are intact, the reverse flow in the radial artery can be used as a pedicle to support the overlying radial forearm skin paddle. The distal pedicle allows the flap to be rotated to cover hand defects.
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