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

Abstract

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. Key words: Nerve regeneration; Peripheral nerves; Models,animal; Gaps