BACKGROUND: Some studies demonstrate that allogenic peripheral nerve segment embedded subcutaneously significantly reduce the infiltration of lymphocyte and decrease immunological reaction. OBJECTIVE: To observe the gross shape, optical and electron microscope results of allogenic nerve segment in rats 2 weeks after subcutaneous embedment, and compare with subcutaneous emdedment of autologous nerve segment. DESIGN: A randomized and controlled experiment. SETTING: Department of Orthopaedics of Fifth People’s Hospital of Zhengzhou; Department of Orthopaedics, First Hospital Affiliated to Chongqing Medical University. MATERIALS: Totally 30 adult healthy Wistar male rats , with body mass of (200±20) g, were enrolled . Ten rats were chosen as the donors of allogenic nerve transplantation. The other 20 rats were randomly divided into 2 groups: allogenic nerve embedment group and autologous nerve embedment group, with 10 rats in each one. JEM-1220 transmission electron microscope (Japan) and Olympus BX50 optical microscope (Japan) were used. METHODS: This experiment was carried out at the laboratory of Orthopaedic Department, Chongqing Medical University from October 2000 to April 2002.① Sciatic nerve of donor rats for allogenic nerve transplantation was cut off at 5 mm distant from pelvic strait.15 mm sciatic nerve segment was chosen from lateral part as graft. allogenic nerve embedment group: 15 mm sciatic nerve form the donor rats was embedded in the posterior part of right legs. Autologous nerve embedment group: 15 mm sciatic nerve segment of autologous left side was embedded in the posterior side of right legs. ② Nerve segment embedded subcutaneously was taken out at postoperative 2 weeks and performed gross observation; then 5 samples chosen randomly respectively from 2 groups and given haematoxylin-eosin staining and observation under optical microscope (×400);The other 5 samples were made into ultrathin sections(0.5 μm)and observed under transmission electron microscope(×17 000). MAIN OUTCOME MEASURES: Gross shape, optical and electron microscope results of nerve segments of rats between two groups at 2 weeks after subcutaneous embedment. RESULTS: ① Results of gross observation: Appearance of nerve segment was similar between 2 groups. ②Results of optical observation: medullary sheath denaturation, axonotmesis, vascular engorgement, desmoplasia of adventitia and infiltration of inflammatory cells were all found in both 2 groups. Inflammatory reaction was a little more severe in the allogenic nerve embedment group than in the autologous nerve embedment groups. ③Results of electron microscope : Similar cataplasia and denaturation of medullary sheath and cataplasia of Schwann cell were all found in the 2 groups. CONCLUSION: Some inflammatory reaction occurs after allogenic nerve embedment, but the activity of Schwann cell is similar to that of peripheral nerve after autologous nerve embedment. BACKGROUND: Some studies demonstrate that allogenic peripheral nerve segment embedded subcutaneously significantly reduce the infiltration of lymphocyte and decrease immunological reaction. OBJECTIVE: To observe the gross shape, optical and electron microscope results of allogenic nerve segment in rats 2 weeks after subcutaneous embedment, and compare SET: Department of Orthopedics of Fifth People’s Hospital of Zhengzhou; Department of Orthopedics, First Hospital Affiliated to Chongqing Medical University. MATERIALS: Totally 30 adult healthy Wistar male rats, with the body mass of (200 ± 20) g, were enrolled. Ten rats were chosen as the donors of allogenic nerve transplantation. The other 20 rats were differentiated into 2 groups: allogenic nerve embedment group and autologous nerve embedment group, with 10 rats in each one. JEM-1220 transmission electron microscope (Japan) and METHODS: This experiment was carried out at the laboratory of Orthopedic Department, Chongqing Medical University from October 2000 to April 2002. ① Sciatic nerve of rats for allogenic nerve transplantation was cut off at 5 mm allogenic nerve embedment group: 15 mm sciatic nerve form the donor rats was embedded in the posterior part of the right legs. Autologous nerve embedment group: 15 mm sciatic nerve segment of autologous left side was embedded in the posterior side of the right leg. 2 Nerve segment embedded subcutaneously was taken out at postoperative 2 weeks and performed gross observation; then 5 samples selected randomly from 2 groups and given haematoxylin-eosin staining and observation under optical microscope (× 400); The other 5 samples were made into ultrathin sections (0.5 μm) and observed under transmission electro n microscope (× 17 000). MAIN OUTCOME MEASURES: Gross shape, optical and electron microscope results of nerve segments of rats between two groups at 2 weeks after subcutaneous embedment. RESULTS: ① Results of gross observation: Appearance of nerve segment was similar between 2 groups. ② Results of optical observation: medullary sheath denaturation, axonotmesis, vascular engorgement, desmoplasia of adventitia and infiltration of inflammatory cells were all found in both 2 groups. Inflammatory reaction was a little more severe in the allogenic nerve embedment group than in the autologous nerve Results of electron microscope: Similar cataplasia and denaturation of medullary sheath and cataplasia of Schwann cell were all found in the 2 groups. CONCLUSION: Some inflammatory reaction occurs after allogenic nerve embedment, but the activity of Schwann cell is similar to that of peripheral nerve after autologous nerve embedment.