The effect of pre-operative conventional and hyperfractionated radiotherapy schedules on wound healing and tensile strength in rats: an experimental study.

We examined the effects of pre-operative conventional and hyperfractionated radiotherapy schedules on wound healing and tensile strength in 90 female Wistar rats weighing between 182 and 240 g. The animals were randomized into three groups (n = 30 each). Group I was sham-irradiated. Group II (conventional) received 20 daily fractions of 200 cGy, to a total dose of 4000 cGy. Group III (hyperfractionated) received 40 fractions of 120 cGy, twice daily, to a total dose of 4800 cGy. Four weeks after radiotherapy, incision and primary repair with simple suturing was performed on one side of the neck. Twenty-one days after wounding, all the rats were sacrificed. Non-parametric Kruskal-Wallis and Mann-Whitney U-tests were used for the statistical analysis of wound tensile strength. The chi-squared test was used for the statistical analysis of the histopathologic findings. The hyperfractionated group had a significantly lower tensile strength than that of the control group (P = 0.03, z = -2.18). According to the histopathologic findings, fibrosis was increased significantly in the hyperfractionated group as compared to the other groups (P = 0.038, chi2 = 6.52). Hyperfractionated radiotherapy significantly reduced the wound tensile strength in the early evaluation period as compared to the control group.