This flap can serve as innervated fasciocutaneous flap or as de-epithiliazed subcutaneous fascial flap. The lateral arm flap is based on the posterior radial collateral vessels (PRCA). The artery is a direct continuation of the deep brachial artery. The draining veins of this area are the venae comitants of the PRCA. The pedicle length is up to 7 cm. The external diameter of this artery is usually 1.5-2.0 mm but some
times can be smaller, 0.8 mm. The vein's diameter ranges from 2.0-2.5 mm. The anatomy of this vascular pedicle is constant, in contrast with the medial arm flap, which has a more variable vascular supply.
The lateral arm flap is innervated by the posterior brachial cutaneous nerve, a proximal branch of the radial nerve (C5-6), giving the flap potential as a sensate flap. Additional sensory supply comes from the posterior antebrachial cutaneous nerve which divides at the distal upper arm, with the upper branch supplying the posterior inferior upper arm and the lower branch supplying the lateral side of the arm and elbow.11
The dimensions of the skin flap can be up to 8 x 15 cm. The surface markings that are important in planning include:
a. a line that joins the deltoid insertion with the lateral epycondyle (this line marks the lateral intermuscular septum and the course of the PRCA), and b. design the flap with this line as the central vascular axis. The deep fascia is included in the flap, but it also can be harvested based on the PRCA pedicle alone, and this kind of flap can be advantageous in cases where thin well-vascularized coverage is required and for coverage of areas where tendon gliding is required.12
The distal territory is thin and is innervated by the lateral brachial cutaneous nerve of the arm, and is often hairless. In addition, vascularized bone (humerus) may be harvested with this flap for composite reconstruction13 (Fig. 8.1).
The periostal blood supplying from the PRCA will allow a vascularized bony segment 10 cm long and 1 cm wide to be included with the skin flap.
The patient position is supine, arm draped to allow free movement: lying on an arm table or fixed across the chest. A tourniquet is recommended but sometimes is difficult to maintain during proximal dissection. Dissection begins with a posterior incision to triceps muscle fascia. The flap is raised sub-fascially and skin is sutured to the fascia to prevent sheering. The posterior fascia is elevated exposing the lateral head of the triceps. Continue dissection to the anterior border of triceps muscle. Here the fascia dives deep and inserts into the humerus. Perforators are now seen in the septum. An anterior incision down to fascia is made. The anterior fascia over the brachialis and the brachio-radialis muscle is incised and follows the level of the periosteum of the humerus. The distal continuation of the PRCA is ligated. Separate the fascial septum as close as possible to the periosteum. The pedicle is followed proximally under the triceps muscle into the spiral groove. The lower cutaneous nerve is separated from the radial nerve. The flap elevation technique should be modified when the fasciocutaneous flap is designed to include vascularized bone (humerus) and tendon (triceps).
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