Experimental animal model proving the benefit of primary defatting of full-thickness random-pattern skin flaps by suppressing "perfusion steal".

Abstract

The value of primary flap defatting remains unclear. This experimental animal study provides a novel theory on the problem of primary defatting, "steal of perfusion" to the skin by fat. This theory is based on the fact that the fat brings blood supply to the proximal flap portion but blood is sequestered in the fat of the distal flap portion, to the disadvantage of skin perfusion. Fifteen full-thickness random-pattern skin flaps, with a 3:1 length-to-width ratio, elevated on the necks of pigs and then left in situ on a plastic sheet interposed between the flap and the deep vascularization from the muscle, were compared with 15 identical contralateral flaps, defatted in the distal half. In the 15 nondefatted flaps, necrosis of the distal half of the flap was observed. Among the 15 defatted flaps, no necrosis was observed in four defatted flaps, partial necrosis was seen in five defatted flaps, concentric necrosis in three defatted flaps, partial necrosis in two defatted flaps, and necrosis in one defatted flap. Necrosis in defatted flaps was significantly less than that in nondefatted flaps (25.6 +/- 21.8 percent of flap surface versus 50 +/- 2.7 percent; p < 0.001). There is a benefit to primary defatting. Perfusion steal exists for pedicular and peripheral vascularization. Primary partial defatting of a random-pattern flap is beneficial for distal perfusion, which is attributed to suppression of perfusion steal. Complete defatting is detrimental to flap survival. The fat is indispensable for perfusion of the proximal flap portion and is paradoxically detrimental for the distal region.