This study investigates the histomorphologic and functional effects of external-beam irradiation on peripheral nerve regeneration in the rat model. All animals received a 1.5-cm interposition isogeneic nerve graft to the right posterior tibial nerve. Group 1 animals served as controls and Groups 2 and 3 received fractionated postoperative irradiation doses of 66 and 106 Gy, respectively. All animals were evaluated for functional recovery with monthly walking-track analysis. At the end of 8 months, the animals were sacrificed and segments of the grafted and distal nerve were harvested for histomorphologic analysis. A statistically significantly fewer number of axons were found in the distal segment of the irradiated specimens, compared to controls. There was no significant difference in the nerve-fiber density of the grafted or distal segments, compared to controls. Functional evaluation by walking-track analysis showed no difference between the irradiated groups and controls over the length of the study. These results suggest that acute nerve grafting of nerve defects in the face of planned postoperative irradiation is safe.
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