Experimental model for transplantation of a modified free myocutaneous gracilis flap to an irradiated neck region in rats.

In 102 Wistar rats (male, weight 300-500 g), a modified free myocutaneous gracilis flap was obtained from the groin and transplanted to the neck. To create a pre-irradiated transplant bed, a local area of the neck was irradiated preoperatively with 30 Gy (fractionation: 3 x 10 Gy) in 30 animals, and with 50 Gy (fractionation: 5 x 10 Gy) in a further 30 animals. The interval between preoperative irradiation and transplantation was 4 weeks. Forty-two animals received no such preoperative radiation. The evaluation of healing and the success of the transplanted flap was based on a clinical assessment, carried out on postoperative days 1 7. Testing for significant differences was done nonparametrically using the Kruskal-Wallis test. The survival rate in the nonirradiated animals was 86%. In contrast, the healing of the free flaps in the pre-irradiated transplant bed was significantly lower (P=0.003) 76%, after irradiation with 30 Gy and 50% after 50 Gy. The significant difference (P=0.020) in survival rates after irradiation with 30 and 50 Gy was evidence for the dependence of successful healing on the preoperative radiation dose. Transplantation of the free myocutaneous gracilis flap to a previously irradiated transplant bed in the region of the neck is a suitable model for investigating the healing of free transplants to irradiated tissue. The success rate observed in non-irradiated transplant beds is comparable to that seen with other flap models in rats.