In vivo bone response to calcium sulfate/poly L-lactic acid composite

Calcium sulfate (CS) is an excellent bone graft material not only because of its osteoconduc-tive, biodegradable, biocompatible, and nontoxic properties, but also because of its angiogenic, barrier membrane, and hemostatic properties. The latter make it unique as a bone graft material. Nevertheless, its clinical use for this purpose is limited by its rapid degradation rate: it usually completely degrades in 4 to 5 weeks, often not enough time for bone to grow into a defect. To overcome this limitation, a CS-based bone graft with a controlled degradation profile was developed. Methods: A composite of CS and poly (L-lactic acid) (PLLA) (ratio, 96:4) was developed and a degradation profile of the composite generated. Bone response to pure CS and to this composite at time points ranging from 4 to 16 weeks was studied in the rabbit tibial intramedullary canal model. Results: This composite underwent controlled degradation in vitro and in vivo, taking 16 weeks for complete degradation in both cases. It stimulated stronger bone formation in bone defects than did pure CS. Conclusion: A CS/PLLA composite (ratio, 96:4) is an excellent bone graft material.