Skin flap delay procedures: proximal delay versus distal delay.

An experimental study was designed to determine which portion of a flap, distal or proximal, contributes more to the delay phenomenon. (Since flap necrosis usually occurs in it distal portion, it is often assumed that only this portion of a flap must be delayed to improve flap survival.) Random-pattern pig flank flaps (16 X 3 cm) were used. All control flaps survived to at least 8 cm. Survival of flaps in which the distal half was delayed was not significantly different from that of controls. Survival of flaps in which the proximal half was delayed was significantly greater than undelayed controls. Completely delayed flaps, however, had significantly better survival than any other group. These findings are inconsistent with the metabolic adaptation hypothesis. They suggest that the denervation supersensitivity-arteriovenous anastomosis hypothesis is incorrect. They are consistent with the vascular collateral hypothesis and the new basal capillary shunting hypothesis.