Two years after in vivo implantation of poly(DL-lactide-epsilon-caprolactone) nerve guides: has the material finally resorbed?

Long-term nerve guide studies on nerve regeneration in vivo are scarce. Previously, we showed that small fragments of biomaterial could still be found on the edge of the epineurium of the regenerated nerve after implantation of poly(DL-lactide-epsilon-caprolactone) [poly(DLLA-epsilon-CL), Neurolac(R)] nerve guides. As these nerve guides are assumed to fully resorb, we studied the 2-year degradation and possible long-term foreign body reaction against the nerve guides after implantation in the sciatic nerve of the rat. In addition, the distribution of both collagen type III and IV, and nerve regeneration through the nerve guides were studied and compared with the non-operated control side. The results demonstrate that nerve regeneration took place through the poly(DLLA-epsilon-CL) nerve guides. After 2 years of implantation, biomaterial could not be found macroscopically. Biomaterial fragments in company of multi-nucleated giant cells and macrophages were found along the regenerated nerve tissue. Collagen III and IV were both found around the epineurium and perineurium in the regenerated nerve, the organization of these layers resembled that of the contra-lateral non-operated nerve. Although sufficient nerve regeneration was obtained after long-term implantation in the rat sciatic nerve, biomaterial fragments and foreign body reactions against these fragments, even after 24 months of implantation, could still be found. The poly(DLLA-epsilon-CL), Neurolac nerve guides do resorb, however, not complete up to 2 years of implantation. It is not known whether the remaining biomaterial fragments and foreign body reactions may cause granulomas or other complications after longer implantation periods.