Experimental study of apatite cement containing antibiotics

Long-term systemic administration of high concentrations of antibiotics may have adverse effects on local osmolality and on various organs; the potential for such effects provides a rationale for the direct administration of such drugs to local sites. The ideal material for this purpose should contain adequate amounts of antibiotics and be biocompatible, and be capable of filling bone defects. We used an implant material called apatite cement. Compounded with gentamyicin (GM) and poly-l-lactic acid (PLA), this material has excellent biocompatibility. In vitro and in vivo studies of this new compound (52 Japanese white house rabbits) showed that the release of antibiotic was gradual and that an effective drug concentration was maintained for 2 months. Histologic findings revealed new bone formation from 2 weeks after implantation. Thereafter, new bone formation sequentially increased in volume. Within 24 weeks, new bone was identified even inside cracked implants. The implant we developed was composed of bioactive material and delivered antibiotic at a level that exceeded the minimal inhibitory concentration ofStaphylococcus aureus. Our implant appears to stimulate satisfactory bone formation. An abstract of this paper was presented at the 9th International Symposium on Ceramics in Medicine and the 9th Basic Research Session of the Japanese Society of Orthopedic Surgery