Ten, fifteen and twenty millimeter nerve defects were produced on both trunks of sciatic nerve in 18 rabbits. The stumps of the nerve were enclosed by a silicon tube in the right hind limb (slilcon group) and the left limbs were free (free group). The proximal and distal nerve stumps in both groups were elongated by using a selfdesigned nerve stretching device, and the nerve were gradually stretched by 1mm, 2mm and 3mm per day respectively. when the expected lengths were achieved, the defects of the nerve were managed by endtoend coaptation. The samples were analysed by electrophysiological examination, and light and electron microscopes. Results were as follows: (1) The nerve defect could be repaired by gradual elongation in rabbits; (2) The results of silicon group were superior to the free group; (3) The structure and microcirculation of the nerve would be damaged if the stretching speed exceeded the limit of 2mm per day. But the eventual results following repair by elongation could not reached the normal level.
The changes of nerve function were observed from the study of electrophysiology and histomorphology in 15 rabbits undergoing gradual lengthening of the legs from different rates and magnitudes. The results showed that if the leg was increased at a rate of 1 mm per day would not result in any changes of nerve morphology or functional damage. The conduction rate of the motor nerve and the potential of the muscular action were all normal; if at a rate of 2mm per day, the leg length was increased within 40％, it was still quite safe. It was believed that the peripheral nerve markedly tolerable to gradual lengthening from traction.
Objective To investigate the effect of the sciatic nerve elongation on pain in rats. Methods Thirty-six adult male Wistar rats of SPF grade, weighing 250-300 g. Eighteen of them were randomly divided into 3 groups, 6 rats in each group. They were sciatic nerve elongation group (group A), nerve no-elongation group (group B), and nerve ligation group (group C). The model of 10-mm sciatic nerve defect was established in all 3 groups. The sciatic nerve was extended at a speed of 1 mm/d for 14 days in group A. The group B was only installed with external fixation. The nerve stumps were ligated in the group C. At 3, 7, 10, and 14 days after operation, the foot injury was evaluated by the autotomy scoring scale. At 14 days after operation, the dorsal root ganglia (DRG) of L4-S1 spinal cord of rats in each group was observed by tumor necrosis factor α (TNF-α) immunohistochemical staining, and the primary antibodies were replaced by pure serum as negative control group. Another 18 rats were randomly divided into 3 groups, 6 rats in each group. They were sciatic nerve elongation group (group A1), nerve no-elongation group (group B1), positive control group (group C1). In groups A1 and B1, the 10-mm long sciatic nerve defect model was established by the same method as groups A and B, and then fixed with external fixation. Nerve elongation was done or not done without anesthesia at 3 days after operation. In group C1, no modeling was done and 20 μL 2.5% formaldehyde was injected into the toes. After 90 minutes, the dorsal horn of spinal cord of L4-S1 segment of rats was cutting for c-Fos immunohistochemical staining and the number of positive cells was counted. Primary antibodies were replaced with pure serum as negative control group. Results The autotomy scores of rats in groups B and C gradually increased postoperatively, and group A remained stable at 0.25±0.50. The scores of group C were significantly higher than those of group A and group B at each time point postoperatively (P<0.05). The scores of group A were significantly lower than those of group B at 10 and 14 days postoperatively (P<0.05). TNF-α immunohistochemical staining showed that the TNF-α expression in group A was weak, slightly positive (+/-); in group B was positive (+); in group C was strongly positive (++); and the negative control group had no TNF-α expression (-). c-Fos immunohistochemical staining showed that the c-Fos expressions in groups A1 and B1 were weak positive, in group C1 was strong positive, and negative control group had no c-Fos positive expression. The number of c-Fos positive cells in groups A1, B1, C1, and negative control group were (21.5±6.6), (19.3±8.1), (95.6±7.4), and 0 cells/field, respectively, and group C1 was significantly higher than groups A1 and B1 (P<0.05), there was no significant difference between group A1 and group B1 (P>0.05). Conclusion Nerve elongation does not cause obvious pain neither during the operation of elongation nor throughout the whole elongation.