In vivo investigations on composites made of resorbable ceramics and poly(lactide) used as bone graft substitutes

Porous composites made of poly(L, DL-lactide) (PLA) and ce-tricalcium phosp hate (a-TCP) or the glass ceramic, GB14N, respectively, were investigated i n a loaded implant model in sheep. Six, 12 and 24 months after implantation histological and biomechanical evaluation were performed and compared to a utogenous bone transplants. No significant differences were observed betwee n the composites. After 6 months, the interconnecting pores of the alpha -T CP-composite and the GB14N-composite were filled with newly formed bone (14 +/- 5% or 29 +/- 15% of the implant, respectively) and soft tissue (30 +/- 9% or 21 +/- 12% of the implant, respectively). Only a mild inflammatory r esponse was observed. The reaction was similar after 12 months. However, af ter 24 months a strong inflammatory reaction was seen. The newly formed bon e was partly osteolytic. The adverse reaction occurred simultaneously to a significant reduction of the PLA component. The histological results were r eflected by the biomechanical outcomes. Both composites showed compression strengths in the range of the autologous bone graft until 12 months of impl antation. After 2 years, however, the strengths were significantly decrease d. It is concluded that the new composites cannot yet be used for clinical application. An improvement in biocompatibility might be reached by a bette r coordination of the degradation times of the polymer and the ceramic comp onent. (C) 2001 John Wiley & Sons, Inc.