AXONAL REGROWTH THROUGH COLLAGEN TUBES BRIDGING THE SPINAL-CORD TO NERVE ROOTS

The capacity of central nervous system (CNS) axons to elongate from th e spinal cord to the periphery throughout a tubular implant joining th e ventral horn of the spinal cord to an avulsed root was investigated in a model of brachial plexus injury, The C5-C7 roots were avulsed by controlled traction and the C6 root was bridged to the spinal cord ove r a 3 mm gap by the use of a collagen cylinder containing or not conta ining an autologous nerve segment, or an autologous nerve graft, Nine months later, the functionnality and the quality of the axonal regrowt h was evaluated by electrophysiology, retrograde labelling of neurons, and histological examination of the gap area, A normal electromyogram of the biceps was observed in all animals where the C6 root was bridg ed to the spinal cord, The mean average amplitude of the motor evoked potentials was comprised between 17.51 +/- 12.03 mu V in animals repai red with a collagen cylinder, and 27.83 +/- 22.62 mu V when a nerve se gment was introduced in the tube, In nonrepaired animals spontaneous p otentials reflecting a muscle denervation were observed at electromyog raphy, Retrograde labelling indicated that a mean number of 58.88 +/- 37.89 spinal cord neurons have reinnervated the biceps in animals repa ired with a tube versus 78.38 +/- 62.11 when a nerve segment was intro duced in the channel, and 97.25 +/- 56.23 in nerve grafting experiment s, Analyses of the repair site showed the presence of numerous myelina ted regenerating axons, In conclusion, our results indicate that spina l cord neurons can regenerate through tubular implants over a 3 mm gap , and that this axonal regrowth appeared as effective as in nerve graf ting experiments, The combination of an implant and a nerve segment di d not significantly increase the regeneration rate. (C) 1997 Wiley-Lis s, Inc.