甲壳质套管桥接周围神经长度极限的研究

A study on the maximal nerve defect length bridgeable by a chitin conduit

目的 通过采用不同间隙套接修复大鼠坐骨神经损伤的实验研究,探讨甲壳质套管桥接修复周围神经损伤的长度极限.方法 SPF级健康成年雄性SD大鼠24只,于大鼠右侧坐骨神经分叉处以上5 mm建立坐骨神经离断伤模型,部分切除坐骨神经后使用甲壳质套管桥接修复,使神经断端间留有2、5、8和10 mm间隙.8周后常规锇酸染色,镜下观察套管远端有髓神经纤维数目、轴突平均面积、髓鞘平均厚度及腓肠肌平均湿重,并进行定量组织学分析.结果 术后8周显示2 mm小间隙组神经纤维已有80%再生,再生效果最佳,与其他组相比差异有统计学意义（P＜0.01）.随着间隙距离逐渐增加,神经纤维再生效果逐渐变差;5 mm间隙组再生约60%,效果优于8 mm间隙组（P＜0.01）;8 mm间隙组再生约20%,优于10 mm间隙组（P＜0.01）;10 mm间隙组只有1%有髓神经纤维成功长入远端,肌肉湿重降至正常的42.9%.结论 使用甲壳质套管桥接修复大鼠坐骨神经损伤时,2 mm左右小间隙套接修复效果最佳,5 mm间隙是修复后周围神经功能得到恢复的极限间隙,10 mm是神经单靠趋化性、营养作用再生的最大间隙.

Objective To investigate the maximal defect length of a peripheral nerve that can be effectively bridged by a chitin conduit by repairing rat sciatic nerve gaps of various lengths with a chitin tube. Methods The right sciatic nerve of 24 SPF-class healthy adult male SD rats was transected at 5 mm proximal to the bifurcation. A segment of nerve was removed to leave a gap of 2, 5, 8 and 10 mm in length according to group assignment. The gap was bridged by a chitin conduit. Eight weeks after the surgery, the nerve distal to the tube was harvested and stained with osmic acid to acquire number of myelinated nerve fibers, axon area and myelin sheath thickness. Wet weight of the gastrocnemius muscles was obtained as well. Results In the 2 mm gap group 80％ nerve fibers had regenerated into the distal nerve stump 8 weeks postoperatively. This regeneration was significantly better than those in the other gap groups（ P ＜ 0.01）. The longer the gap, the worse the regeneration. The percentage of nerve fibers that regenerated into the distal nerve stump was 60％ for the 5 mm gap, 20％ for the 8 mm gap, and 1％ for the 10 mm gap. Each was significantly better than next size up in nerve defect. Conclusion When chitin conduits are used to bridge a rat sciatic nerve defect, the optimal length of the gap for nerve regeneration is around 2 mm. The longest bridgeable defect that allows functional recovery is 5 mm. Nerve regeneration is seriously affected when the gap is longer than 10 mm.