Long-term in vitro degradation and in vivo evaluation of resorbable bioceramics

An essential criterion for the selection of resorbable bioceramics is their ability to degrade inside human body within a reasonable time frame. Furthermore, if the bioceramic can release beneficial ions, such as strontium, as it degrades, recovery time might be shortened. The present study demonstrates that strontium-containing calcium sulfate (Sr,Ca)SO(4) can fulfill these criteria. A long-term in vitro degradation analysis for 12 weeks using sintered (Sr,Ca)SO(4) discs in phosphate buffered solution (PBS) was conducted. The sintered (Sr,Ca)SO(4) disc was then implanted into defects in the distal femur of rats. The degradation rate of (Sr,Ca)SO(4) discs showed a strong dependence on the Sr content. Similar results were observed between the long-term in vitro degradation analysis and the in vivo evaluation. The sintered (3.8%Sr,Ca)SO(4) disc lost more than 80% of its initial weight after soaking in PBS with shaking at 37 °C for 12 weeks. After 12 weeks in vivo, the remaining volume of the (3.8%Sr,Ca)SO(4) disc within the bone defect was ~25%. Over the same time period, new bone was formed at a relative volume of 40%. This study demonstrates the potential of (Sr,Ca)SO(4) bioceramic, and the benefits of using a long-term degradation test during the evaluation of resorbable bioceramics.