Near-terminus axonal structure and function following rat sciatic nerve regeneration through a collagen-GAG matrix in a ten-millimeter gap

The objectives of this study were to evaluate the regenerated axon structur e at near-terminal locations in the peroneal and tibial branches 1 year fol lowing implantation of several tubular devices in a 10-mm gap in the adult rat sciatic nerve and to determine the extent of recovery of selected senso ry and motor functions. The devices were collagen and silicone tubes implan ted alone or filled with a porous collagen-glycosaminoglycan matrix. Intact contralateral nerves and autografts were used as controls. Nerves were ret rieved at 30 and 60 weeks postoperatively for histological evaluation of th e number and diameter of regenerated axons proximal and distal to the gap a nd in the tibial and peroneal nerve branches, near the termination point. S everal functional evaluation methods were employed: gait analysis, pinch te st, muscle circumference, and response to electrical stimulation. A notable finding was that the matrix-filled collagen tube group had a significantly greater number of large-diameter myelinated axons (greater than or equal t o 6 mu m in diameter) in the distal nerve branches than any other group, in cluding the autograft group. These results were consistent with previously reported electrophysiological measurements that showed that the action pote ntial amplitude for the A fibers in the matrix-filled collagen tube group w as greater than for the autograft control group. Functional testing reveale d the existence of both sensory and motor recovery following peripheral ner ve regeneration through all devices; however, the tests employed in this st udy did not show differences among the groups with regeneration. Electrical stimulation in vivo showed that threshold parameters to elicit muscle twit ch were the same for reinnervating and control nerves. The investigation is of importance in showing for the first time the superiority of a specific fully resorbable off-the-shelf device over an autograft for bridging gaps i n peripheral nerve, with respect to the near-terminus axonal structure. (C) 2000 Wiley-Liss, Inc.