Answer:
The flap is based on the septocutaneous branches of the anterior tibial artery as it passes through the middle third of the leg. It is usually rotated proximally to cover the upper third of the tibia. Alternatively, it can be distally rotated to provide coverage to the lateral malleolus. Greater length and arc of rotation distally can be achieved with division of the anterior tibial artery proximally. Distally based flaps, however, may be unreliable because of inadequate reverse flow in the anterior tibial artery. Also, the patency of the posterior tibial and peroneal arteries should be confirmed preoperatively. Venous insufficiency is also considered a relative contraindication to distally based flaps. The skin overlying the muscle can be included or only fascia without skin can be used to minimize the donor defect. Although, theoretically the anterior tibialis is available for use as a free flap based on the anterior tibial artery, the required sacrifice of this artery and potential for lower extremity vascular insufficiency make it a less desirable donor site for use as in microvascular free flaps.