Magnifying effect of conduit bridging in number of nerve fibers of broken peripheral nerves:experiment with rats

Abstract

To observe the magnifying effect of conduit bridging in number of nerve fibers of broken peripheral nerves. Fifty Sprague-Dawley rats were randomly divided into five equal groups. Group A underwent transection of the sciatic nerves and bridging of the complete proximal sciatic nerve stump and the distal sciatic stump in a conduit sutured with 8 - 0 nylon chord with a 2-mm gap. In Group B, the sciatic nerve was transected, the proximal stump was divided into tibial nerve and common peroneal nerve bundles 5 mm proximal to the transection site, the common peroneal nerve bundle was ligated and transected, and then the proximal stump of the tibial nerve and the distal sciatic stump were bridged with a conduit with a 2-mm gap. In Group C, the sciatic nerve was transected, the proximal stump was divided into tibial nerve and common peroneal nerve bundles 10 mm proximal to the transection site, the tibial nerve bundle was ligated and transected, and then the proximal stump of the common peroneal nerve and the distal sciatic stump were bridged with a conduit with a 2-mm gap. In group D, the tibial nerve was transected 5 mm distal to the branch site, 2/3 of the tibial nerve fibers were ligated and transected, and then the remnant 1/3 fibers of the proximal stump of tibial nerve were bridged to the distal stump of tibial in a conduit. In Group E the tibial nerve was transected 5 mm distal to the branch site, and then the complete proximal tibial nerve stump was bridged to the distal stump of tibial nerve in a conduit Electrophysiological examination was conducted 1, 2, 4, and 12 weeks later. Pathological examination was performed with immunohistochemistry, HE staining and osmic acid staining. One week after surgery, edema and ulcer in the hind limbs were found in most rats; toe necrosis was seen in part of the rats, and since 3 weeks later these pathological changes began to disappear gradually. The motion of hind limbs recovered since 4 weeks after the surgery. Osmic acid staining 12 weeks later showed that the numbers of distal myelin sheath at the distal end were more than that in the proximal end by 34.4% in Group A, 39.6% in Group B, 80.4% in Group C, 101.1% in Group D, and 48.9% in Group E. The axon number distal to the transaction site becomes significantly more than that at the proximal end after bridging. The magnification effect of the bridging of homologous nerve is greater than that of non-homologous nerve. It is possible to repair the thicker nerve at the distal broken end with thinner nerve at the proximal end clinically.