BACKGROUND: Some experimental studies demonstrate that subcutaneous implant of allograft can significantly decrease lymphocyte infiltration and reduce immunological reaction. However, compared with autologous nerve grafting, what is the effect of nerve regeneration after repair? OBJECTIVE: To observe the local nervous status of the detected part of sciatic nerve repaired through subcutaneously implanting peripheral nerve allograft, and compare the effect with fresh autologous nerve grafting. DESIGN: Contrast observation. SETTING: Departments of Orthopaedics of Zhengzhou Fifth People’s Hospital and First Hospital Affiliated to Chongqing Medical University. MATERIALS: Totally 30 healthy adult Wistar male rats, with body mass of (200±20)g, were enrolled. Optical microscope (Olympus biological microscope BHS, Japan), Electron microscope (H-600, Japan), CM-2000 biomedical image analysis system(CM-2000,Beihang) and myoelectricity scanner (KEYPOINT, Denmark) were used in this experiment. METHODS: This experiment was carried out in the Orthopaedic Laboratory of Chongqing Medical University between October 2000 and April 2002. ① Six rats were chosen as the donors for allogenic nerve grafting, and 15 mm sciatic nerve segment was chosen as graft. The other rats were randomly divided into two groups: allogenic nerve grafting group and autologous nerve grafting group, with 12 rats in each group. In the allogenic nerve grafting group, a skin incision was made on the posterior side of right thigh, and subcutaneous blunt dissection was performed prorsally a little, then allograft was implanted. Two weeks later, sciatic nerve was exposed at the posterior side of left thigh and cut respectively at 5 mm and another 10 mm away from pelvis. The donor nerve (with connective tissue veil) implanted subcutaneously on the right thigh was taken out. Sectioned connective tissue at the proximal end was trimmed and that at the distal end as done but reserved 10 mm in length, and inosculated antegradely at the nerve defect on the left side with 11/0 nylon line. Twelve rats in autologous nerve grafting group underwent a 10 mm sciatic nerve defect incision on the right thigh and implant of fresh sciatic nerve from left thigh. The incision on the left thigh was repaired in situ. ②2,4,8 and 14 weeks after grafting, the nerve specimen of anastomosis segment was observed under optical microscope. Fourteen weeks after grafting, the ultrathin section of distal sciatic nerve was observed under transmission electron microscope. The number and size of regenerated axons at the cross section of anastomosis of proximal and distal sciatic nerve were analyzed with biomedical image analysis system. Neuroelectrophysiological change of in vivo sciatic nerve was detected with myoelectricity scanner. ③ t test was used in the comparison of difference of measurement data. MAIN OUTCOME MEASURES: ① Observation of anastomosis part of sciatic nerve under optical and electron microscopes in the two groups. ② Comparison of motor nerve conduction velocity, latent period and action potential peak as well as the number and size of cross-section of anastomosis part of proximal and distal sciatic nerve between two groups. RESULTS: ①Observation under optical microscope:Two weeks after grafting, neve axon of repaired region broke and medullary sheath denatured in the allogenic nerve grafting group and autologous nerve grafting group. At the same time, vascular engorgement and a little lymphocytes infiltration were found in the autologous nerve grafting group, but those were found worsened in the allogenic nerve grafting group. Four weeks after grafting, the intensity of the inflammatory reaction was similar between two groups, some collagen fibers at the proximal end proliferated; 8 weeks after grafting, the inflammatory reaction ended basically and the collagen fibers proliferated obviously in the two groups. ② Observation under electron microscope: Fourteen weeks after grafting, the structure of epineurium was in integrity and there were no obvious differences in perineurium and endonurium between two groups. A large number of myelinated nerve fibers and a few unmyelinated nerve fibers regenerated. The structure of myelin sheath was in integrity. ③The number and size of regenerated axons of anastomosis of proximal and distal sciatic nerve had no significant difference 14 weeks after grafting [(575.500±7.495)vs(585.700±11.172) axons/visual field;(389.300±49.073)vs(407.600±0.283)axons/visual field;(6 423.830±119.911)vs(6 695.36±84.287) μm2/visual field;(5 980.110 ±74.572)vs(5 980.110±74.572) μm2/visual field] (P > 0.05). ④ Neuroelectrophysiological examination showed that there were no significant differences in motor nerve evoked potential latent period[(1.420±0.346)vs (1.237±0.250) ms] , motor nerve conduction velocity [(12.120±0.906)vs(13.020±0.599) m/s]and latent period of sciatic nerve [(0.500±0.380)vs (1.250±1.067) mV] of rats between two groups (P > 0.05). CONCLUSION: Although subcutaneous implant of peripheral nerve allograft has some inflammatory reactions, no obvious rejection is found. Repair results of two groups show that subcutaneous implant of allograft can promote nerve regeneration, which is similar to autologous nerve grafting. BACKGROUND: Some experimental studies demonstrate that subcutaneous implant of allograft can significantly decrease lymphocyte infiltration and reduce immunological reaction. However, compared with autologous nerve grafting, what is the effect of nerve regeneration after repair? OBJECTIVE: To observe the local nervous status of the detected part of sciatic nerve repaired through subcutaneously implanting peripheral nerve allograft, and compare the effect with fresh autologous nerve grafting. DESIGN: Contrast observation. SETTING: Departments of Orthopedics of Zhengzhou Fifth People’s Hospital and First Hospital Affiliated to Chongqing Medical University. MATERIALS: Totally 30 (adult) Wistar male rats, with body mass of (200 ± 20) g, were enrolled. Optical microscope (Olympus biological microscope BHS, Japan), Electron microscope (H-600, Japan), CM-2000 biomedical image analysis system -2000, Beihang) and myoelectricity scanner (KEYPOINT, Denmark) were used in this experiment. MET HODS: This experiment was carried out in the Orthopedic Laboratory of Chongqing Medical University between October 2000 and April 2002. ① Six rats were chosen as the donors for allogenic nerve grafting, and 15 mm sciatic nerve segment was chosen as graft. The other rats were randomly divided into two groups: allogenic nerve grafting group and autologous nerve grafting group, with 12 rats in each group. In the allogenic nerve grafting group, a skin incision was made on the posterior side of right thigh, and subcutaneous blunt dissection was performed prorsally a little, then allograft was implanted. Two weeks later, sciatic nerve was exposed at the posterior side of left thigh and cut respectively at 5 mm and another 10 mm away from pelvis. The donor nerve (with connective tissue veil) implanted subcutaneously on the right thigh was taken out. Sectioned connective tissue at the proximal end was trimmed and that at the distal end as done but reserved 10 mm in length, and inosculated a ntegradely at the nerve defect on the left side with 11/0 nylon line. Twelve rats in autologous nerve grafting group underwent a 10 mm sciatic nerve defect incision on the right thigh and implant of fresh sciatic nerve from left thigh. The incision on the left 2, 4, 8 and 14 weeks after grafting, the nerve specimen of anastomosis segment was observed under optical microscope. Fourteen weeks after grafting, the ultrathin section of distal sciatic nerve was observed under transmission electron microscope. and size of regenerated axons at the cross section of anastomosis of proximal and distal sciatic nerve were analyzed with biomedical image analysis system. Neuroelectrophysiological change of in vivo sciatic nerve was detected with myoelectricity scanner. ③ t test was used in the comparison of difference of measurement data. MAIN OUTCOME MEASURES: ① Observation of anastomosis part of sciatic nerve under optical and electron microscopes in the two groups. ② Comparison of motor nerve conduction velocity, latent period and action potential peak as well as the number and size of cross-section of anastomosis part of proximal and distal sciatic nerve between two groups. RESULTS: ①Observation under optical microscope: Two weeks after grafting, neve axon of repaired region broke and medullary sheath denatured in the allogenic nerve grafting group and autologous nerve grafting group. at the same time, vascular engorgement and a little lymphocytes infiltration were found in the autologous nerve grafting group, but those were found worsened in the allogenic nerve grafting group. The intensity of the inflammatory reaction was similar between two groups, some collagen fibers at the proximal end proliferated; 8 weeks after grafting, the inflammatory reaction ended basically and the collagen fibers proliferated obviously in the two groups. ② Observation under electron microscope: Fourteen weeks after grafting, the structure of epineurium was in integrity and there were no obvious differences in perineurium and endonurium between two groups. A large number of myelinated nerve fibers and a few unmyelinated nerve fibers regenerated. The structure of myelin sheath was in integrity. ③ The number and size of regenerated axons of anastomosis of proximal and distal sciatic nerve had no significant difference for 14 weeks after grafting [(575.500 ± 7.495) vs (585.700 ± 11.172) axons / visual field; (389.300 ± 49.073) vs (407.600 ± 0.283) axons / visual field; (6 423.830 ± 119.911) vs (6 695.36 ± 84.287) μm 2 / visual field; (5 980.110 ± 74.572) vs (5 980.110 ± 74.572) μm 2 / visual field respectively (P 0.05) .④Neuroelectrophysiological examination showed that there were no significant differences in motor nerve evoked potential latent period [(1.420 ± 0.346 vs 1.237 ± 0.250) ms], motor nerve conduction velocity [(12.120 ± 0.906 vs 13.020 ± 0.599) m / s] and latent period of sciatic nerve [(0.500 ± 0.380) vs (1.250 ± 1.067) mV] of rats between two groups ( P> 0.05). CONCLUSION: Although subcutaneous implant of peripheral nerve allograft has some inflammatory reactions, no obvious rejection is found. Repair results of two groups show that subcutaneous implant of allograft can promote nerve regeneration, which is similar to autologous nerve grafting.