Long-term evaluation of rat peripheral nerve repair with end-to-side neurorrhaphy

This study was designed to assess long-term reinnervation of end-to-side ne urorrhaphy in the rat. The cut right peroneal nerve was repaired and suture d to the side of the intact tibial nerve. Both the extent of reinnervation and the integrity of the intact donor nerve were evaluated in 48 Sprague-Da wley rats randomly treated with fresh or delayed nerve repair with or witho ut perineurotomy. Evaluations included nerve conduction velocity (NCV) of b oth the peroneal and tibial nerves, dry muscle weight, and histologic exami nation (neurofilament stain and morphometric assessment) at 8 and 12 months postoperatively. Although animals treated with perineurotomy tended to hav e better NCV and dry muscle weight recovery than those without, the differe nce was not statistically significant. No difference was observed between f resh and predegenerated nerve repair. The mean total (all four subgroups) N CV recovery rates were 87 percent and 94 percent for the peroneal nerve, an d 93 percent and 95 percent for the tibial nerve, compared to the contralat eral intact nerves, at 8 and 12 months, respectively. Tibialis anterior mus cle mass measurements revealed a recovery in dry muscle weight of about 85 percent and 89 percent at 8 and 12 months, respectively, compared to the in tact contralateral tibialis anterior muscles. Histologic studies with neuro filament staining revealed numerous axons at the distal end of the peroneal nerve in all groups, indicative of myelinated axonal regeneration. Morphom etric analysis demonstrated that the presence of a window in the perioneuri um improved the histologic picture. The mean number of myelinated fibers at 12 months postoperatively was significantly higher in animals with a perin eurotomy window (compared to without) in both fresh and predegenerated nerv e repair subgroups, respectively (p <0.05). These results indicated that en d-to-side neurorrhaphy permits axonal regeneration from the intact donor ne rve and is associated with satisfactory recovery. The effect of the procedu re on the donor nerve was negligible.