Anatomical bases of the bypass-flap: study of the thoracodorsal axis.

Cutaneous tissue loss in patients with lesions on the arterial axes remains difficult to treat. Currently, combined surgery associating distal bypass and free flap seems to be the technique that yields the best results. The hemodynamic advantages of this technique, recently demonstrated, are the distal resistance and the increase in bypass flow. Nevertheless, it is complex and its indications limited. Two major drawbacks can be noted: The increasing risk of thrombosis due to the multiplication of anastomoses on the same arterial axis and the deterioration in venous autograft. To overcome these inconveniences we propose a new technique that we call bypass-flap (BF): the graft of an anatomical entity comprised of one artery and one flap. This graft secures the cover of tissue loss and the revascularization of the limb. Apart from its combined nature this technique presents three major advantages. The arterial autograft is superior to the venous graft, the gradually decreasing diameter of the artery secures the congruence of the anastaomoses, and the arterial flow of the graft is higher than a simple bypass due to the joint vascularization of the flap. The arterial graft includes the subscapular and the thoracodorsal arteries. The free flap is composed of serratus anterior muscle supplied by branches of the graft. This investigation studied the feasibility of the bypass flap and determined the length and diameter of the arterial graft and its muscular branch. Forty anatomical preparations were performed on 20 cadavers. The dissections were performed after injection of Rhodorsil. The anatomical feasibility of the bypass flap was confirmed in 37 cases. The total length of the arterial graft that preserved an external diameter above 2 mm was measured at 13 cm (8.5-15.5). This includes the subscapular artery and the thoracodorsal artery with its intramuscular part (if external diameter of that part always above 2 mm). The length of the pedicle of the serratus anterior flap was measured at 7.5 cm (3.0-12.5 cm).