Bone response to degradable thermoplastic composite in rabbits

The aim of this study was to evaluate biologic behavior of a composite of bioactive glass (BAG) (S53P4) and copolymer of poly( -caprolactone-co- -lactide) in experimental bone defects in rabbits. Twenty New Zealand white rabbits were used for the study. Bone defects (4×6 mm) were prepared in the medial surfaces of the femoral condyles and the tibia. Cavities were filled with three different composites: composite with 60 wt% of small BAG granules (granule size <45 μm) and composites with 40 and 60 wt% of large BAG granules (granule size 90–315 μm). Copolymer without BAG was used as a reference material. Follow-up period was 8 and 16 weeks. In the femur at 8 weeks all the samples were partly surrounded by fibrous capsule. New bone formation was noticed in the areas where glass granules were in direct contact with the bone. At 16 weeks fibrous capsule was thinner in all samples. Bone ingrowth was found in the superficial layers of the composites with large glass granules. However, the percent of direct bone contact decreased between 8 and 16 weeks (p<0.05). In the tibia at 8 weeks all the samples showed fibrous encapsulation. At 16 weeks fibrous capsules were thinner or occasionally disappeared. Bone ingrowth was noticed in the samples with large glass granules. Further, new bone formation was found in the medullary cavity. No signs of polymer degradation were seen at any time point. It can be concluded that the composite of BAG (S53P4) and copolymer of poly( -caprolactone-co- -lactide) is biocompatible with the bone tissue within the 16 weeks implantation period.