Soft tissue and cancellous bone reaction to the implantation of novel biodegradable pins and plates in rabbits.

Biodegradable implants for osteosynthesis have had insufficient strength and a fast degradation rate. We produced a polymer based lactide to increase the molecular weight and strength of the implant and delay the degradation rate. This novel fiber-reinforced material in the form of plates and pins was tested in vitro for mechanical performance and in vivo in a neutral mechanical environment to assess biocompatibility. 21 rabbits with implants in the tibia and femoral condyles were killed at 1, 6, 12 months after implantation. Only a mild foreign-body reaction was observed and the implant was encapsulated by a thin 0.8-1.6 mm layer of connective tissue. Only a few lymphocytes and giant cells were detected in the early stages, dense fibroblasts in the middle stage, and giant cells clearing material particles in the late stage. In conclusion, the novel fiber-reinforced polymer based on polylactides was found mechanically superior to former degradable implants and biocompatible, showing no late inflammatory tissue response.