PREFORMATION OF MICROVASCULAR COMPOSITE FREE FLAPS IN THE RAT AS AN ANIMAL-MODEL

For optimal reconstruction of large defects after tumor surgery of the head and neck, composite flaps may be necessary. We describe the desi gn of microsurgically reanastomosed composite skin flaps, using porous polyethylene or titanium implants as a ''back side'' in an animal mod el. The epigastric skin of 48 healthy adult Wistar rats was prepared f or the subdermal insertion of porous polyethylene implants (pore size: 100-200 mu m) and titanium mesh implants having different forms and s izes. Two to 6 weeks after this procedure the flaps were lifted, trans posed to the other side and the epigastric vessels were reanastomosed microsurgically. Eighty-three per cent of the skin flaps containing th e titanium implants survived when the transplantation occurred 2 weeks after insertion of the implants. Concurrently all flaps with the impl anted porous polyethylene (1 mm thick) showed signs of skin necrosis. Survival of the polyethylene loaded flaps improved to 50% when the fla ps were left 4 weeks at the donor site. The influence of the implant f orm on the survival of the flaps was investigated with different impla nt shapes with flap necrosis being greatest when concave implants were used. Histopathological evaluation of the titanium flaps showed a thi n capsule around the implants and a minimal inflammatory reaction. All porous polyethylene implants resulted in a pronounced chronic infecti on. Transplantation of flaps containing perforated metals (such as the titanium mesh) was possible 2 weeks after insertion of the implant, w hereas neovascularization of flaps with porous material required more than 4 weeks growth in situ to ensure at least a 50% viability of the skin. An advantage of the metal implants is the possibility of its use in correcting form by modelling.