Neurovascular Anatomy

The medial antebrachial and lateral antebrachial cutaneous nerves innervate the skin of the volar forearm and inclusion of either nerve provides a potentially sensate free flap (Fig. 46). A commonly used recipient nerve in oral reconstruction is the lingual

Figure 44 De-epithelialized radial forearm free flap with distal marker segment used for repair of an extensive craniofacial defect. Note the defect with communication of the anterior cranial fossa and the nasal cavity (A). The flap is placed over the defect and secured (B). The distal marker skin segment is incorporated into the scalp incision for monitoring purposes.

Figure 44 De-epithelialized radial forearm free flap with distal marker segment used for repair of an extensive craniofacial defect. Note the defect with communication of the anterior cranial fossa and the nasal cavity (A). The flap is placed over the defect and secured (B). The distal marker skin segment is incorporated into the scalp incision for monitoring purposes.

Figure 45 Radial forearm free flap for pharyngeal reconstruction with planned marker segment (arrow) to be incorporated into the neck skin flap.

nerve. The radial artery and venae comitantes are enveloped by fascial extensions from the intermuscular septum. The fascio cutaneous component receives its blood supply from the radial artery via septocutaneous perforators that course through the lateral intermuscular septum between the brachioradialis and flexi carpi radialis.

Muscular perforators provide the vascular supply to the underlying periosteum and radial bone. The vascular pedicle (radial artery and vena comitantes) courses toward the antecubital fossa to the brachial artery. Dissection and freeing of the vascular pedicle between the superior flap edge and brachial artery require division of multiple muscular perforators.

The venae comitantes drain a deep venous system that freely communicates with the superficial system of veins. The much larger superficial venous drainage system fully supports venous outflow and can be used in place of or in addition to the venae comitantes. The superficial cephalic vein over the dorsoradial aspect of the wrist is most often incorporated.

The presence of an intact circulation between the deep and superficial palmar arches is important to ensure that the hand is adequately perfused after the radial artery is sacrificed. The lack of a collateral system may be found in as many as 15% of patients, and can be investigated clinically by performing an Allen's test (56). Edgar V. Allen originally described the Allen's test in 1929 as a noninvasive evaluation of the patency of the arterial supply to the hand of patients with throm-boangiitis obliterans. In the early 1950s, the Allen's test was modified for use as a test of collateral circulation prior to arterial cannulation (57). With respect to the forearm free flap, the Allen's test is used to test the adequacy of the ulnar artery to supply the hand in the absence of the radial artery. It is performed by elevating the hand in question above the patient's head, manually occluding both the radial and ulnar arteries, dropping the hand to the level of the heart, having the patient open and close the fist several times, releasing the ulnar artery, and timing the return of capillary refill to the radial side of the hand. A positive (normal) test should document the return of capillary refill after release of the ulnar artery within 6 s. An Allen's test is not fail-safe and the adequacy of crossover blood flow between the ulnar and radial arteries should also be assessed in the operating room before the radial artery is harvested by temporary occlusion (58). If inadequate crossover exists, the flap should either be abandoned or the radial artery reconstructed with a saphenous vein graft.

After flap harvest, the donor site is covered with a skin graft. It is important to preserve the fragile tendon fascial sheaths (the peritenon) during flap harvest to provide a vascularized bed for the skin graft.

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