Reconstruction of large-sized lumbosacral or sacral defects often is not possible using local or regional flaps, making the use of free flaps necessary. However, the difficulty of any microsurgical procedure in this region is complicated by the need to search for potential recipient vessels to revascularize the flap. In the present case, a free musculocutaneous anterolateral thigh flap to cover a large-sized and deep lumbosacral defect was used. Arterial anastomosis was performed, connecting the cutaneous anterolateral thigh (ALT) perforator to the perforator of the second lumbar artery. In this fashion, the arterial circulation through the flap was flowing reversely through the muscle. The concomitant vein of the descending branch of the lateral circumflex femoral artery was hooked up to the thoracodorsal vein using a long interposition vein graft because the perforator of the second lumbar vein was too small. Postoperative healing was uneventful. In conclusion, a successful reconstruction of a lumbar defect has shown that local perforators in the lumbar area may be accessible for easier perforator-to-perforator anastomoses and that the muscular part of the musculocutaneous ALT flap can survive on retrograde arterial perfusion from a perforator of the skin island.