|Microsurgery: Transplantation and Replantation by Harry J. Buncke, MD, et al.
| The posterior skin incision is made first, extending from the lateral epicondyle to the insertion of the deltoid muscle. In the region of the cutaneous portion of the flap, the incision is carried down through the deep fascia enveloping the triceps muscle. The posterior flap is raised subfascially, tacking the triceps fascia to the skin island to prevent the flap from shearing off and protecting the perforating cutaneous branches of the PRCA within the surrounding fascia of the triceps. Dissection continues from back to the anterior border of the triceps muscle. Here, the fascia dives deeply and inserts into the humerus. It is within this two-leaved fascial envelope (the posterior leaf is the triceps fascia and the anterior leaf is the biceps, brachialis, brachioradialis fascia) that the PRCA lies. When the posterior dissection has been accomplished, the cutaneous perforators will be visible, and one may then adjust the position of the anterior incision to include these vessels in the fasciocutaneous portion of the flap.
To harvest the anterior half of the flap, an incision is made overlying the biceps muscle and carried into the subfascial plane, again tacking the fascia to the skin island. This dissection proceeds anterior to posterior to the insertion of the fascia into the bone at the posterior border of the biceps, brachialis, and brachioradialis muscles. At this point, the cutaneous flap, with its ascending cutaneous perforators, is tethered by the fascia that inserts into the bone. The distal continuation of the PRCA is then transected and ligated, and the two leaves of the fascia are released from their bony insertion. Osseous perforators are ligated as the fascia is separated from the bone. If bone is to be taken with the flap, the segment is outlined, encompassing the fascial insertion. The pedicle is dissected proximally, and great care is taken to identify the radial nerve that lies between the brachialis and brachioradialis muscles. Often the posterior cutaneous nerve of the forearm is so intimately attached to the flap that it cannot be separated and must be sacrificed. The dissection continues proximally until the insertion of the deltoid muscle is reached. Here, the pedicle turns posteriorly and the PRCA can be followed for a short distance as it travels toward the so-called spiral groove on the posterior humeral surface. To obtain the maximal pedicle length, the region of the spiral groove can be entered by dividing the fibers of origin of the lateral head of the triceps from the humeral shaft. These fibers are repaired at the conclusion of surgery. In practice, the greatest length of pedicle that can be obtained is approximately 8 cm. At this level, the smallest outer diameter is 1 mm, but usually the diameter is between 1.5 mm and 2.0 mm.l The paired venae comitantes that accompany the PRCA provide the venous drainage.
Katsaros et al.1 have shown that a donor site of up to 6 cm in anteroposterior diameter may be closed primarily. Donor sites of greater diameters need skin grafting for closure. Whey multiple perforators are found to the proximal and distal portions of the flap, the flap can be cut through in its central area, providing two islands that can be folded to form lining and cover for facial defects, or placed side by side to form a shorter, wider flap.
An area of numbness results along the lateral forearm, innervated by the posterior cutaneous nerve of the forearm. This is usually tolerated well and decreases progressively within the first 6 months after surgery.
PLATE VIII-1. Anatomy
A. The principal surface markings of the flaps are the deltoid insertion and the lateral epicondyle of the humerus. The central axis of the flap lies along this line, which parallels the lateral intramuscular septum.
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