The development of neovascularisation in flap perfabrication with vascular implantation: an experimental study

Femoral arteriovenous pedicles were implanted beneath the abdominal skin in rats (n = 30) to investigate the development of neovascularisation over time. New vessel formation was assessed by micro-angiography and quantified under light microscopy. Flap viability was assessed by dye injection studies at different time intervals. Two weeks after implantation of the vascular pedicles, neovascularisation was confined to the vicinity of the arteriovenous pedicle only and none of the flaps were viable. At 4 and 6 weeks, 4 out of 6 flaps were viable, with new vessel formation being widespread throughout the subcutaneous tissue. All flaps were viable at 8 and 12 weeks. Neovascularisation in the dermis up to the epidermis was observed after 8 weeks. Neovascularisation in the panniculus carnosus showed a steady increase after 6 weeks. There was a decrease in the total number of vessels at 12 weeks compared to 8 weeks but at 12 weeks the diameters of the vessels were considerably larger. Flap survival was best predicted by the amount of neovascularisation in the panniculus carnosus. In this experimental model, it is concluded that prefabricated flaps should be raised at 8 weeks instead of 4 or 6 weeks after the implantation of an arteriovenous pedicle, to reduce the risk of flap failure.