In vivo performance of a new biodegradable polyester urethane system used as a nerve guidance channel

Biodegradable nerve guidance channels (NGCs) represent a promising alternat ive to current clinical nerve repair procedures. To be suitable as a NGC ma terial, the polymer system should possess elastomeric properties and degrad e at a defined rate without interfering with the regenerating environment. Polymers made of non-crystallizable blocks of poly[glycolide-co-(epsilon-ca prolactone)]-diol and crystallizable blocks of poly[(R)-3-hydroxybutyric ac id-co-(R)-3-hydroxyvaleric acid]-diol (PHB) can be modulated so as to respo nd to those criteria. Tubular structures were fabricated from three differe nt types of materials containing either 41, 17 or 8 wt% PHB. Nerve regenera tion through a 10 mm long NGC using a transected sciatic nerve model with a n 8 mm gap was studied in rats at 4, 12 and 24 weeks. Out of 26 implanted N GCs, 23 contained regenerated tissue cables centrally located within the ch annel lumen and composed of numerous myelinated axons and Schwann cells. No significant difference in the degree of regeneration was observed between the various channel types. The inflammatory reaction associated with the po lymer degradation had not interfered with the nerve regeneration process. M acrophages and giant cells surrounded polymer material remnants. A weight l oss of 33, 74 and 88% for polymers containing 41, 17 and 8 wt% PHB was obse rved after 24 weeks by nuclear magnetic resonance (NMR) anaylsis, respectiv ely. In all cases, the polymer fragments had a porous appearance with multi ple surface cracks as evidenced by scanning electron microscopical analysis . Guidance channels made of 8 wt % PHB containing polymer displayed the hig hest degree of degradation at 24 weeks with only small polymer fragments re maining. The present study suggests that this new biodegradable elastomeric polymeric material holds promises for its utilization as nerve guidance ch annels. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.