Answer:
Kolker et al. found that there was no significant difference in outcome (flap failure vs. success) or rates of reoperation between free flaps that were based on recipient vessels proximal to the zone of injury and those based on vessels distal to the zone of injury provided that adequate flow is demonstrated in vessels traversing the zone of injury. Although potentially traumatized vessels in the zone of injury may be more predisposed to vascular occlusive problems, the added risk is not considered significant and is counterbalanced by the technically easier distally based free flap. Moreover proximally based free flaps often require an anastomosis deep within the muscles of the lower extremity as well as a longer tunnel for the pedicle. Vein grafts are more commonly necessary to achieve a proximal anastomosis. These factors which are not as often present in distally based flaps may contribute to greater thrombosis and failure in proximally based free flaps.