EFFECT OF FREEZE-DRIED POLY-L-LACTIC ACID DISKS MIXED WITH BONE MORPHOGENETIC PROTEIN ON THE HEALING OF RAT SKULL DEFECTS

Porous poly-L-lactic-acid discs were prepared by a freeze-drying method (FDPLLA). During preparation of the discs, semipurified bone morphogenetic protein (BMP) was mixed with the poly-L-lactic acid (500 mug BMP per disc). The discs were implanted in the skull defects of rats and retrieved after 2 or 4 weeks. With the FDPLLA/BMP discs, new bone formation was observed at 2 weeks after implantation. On the other hand, plain FDPLLA discs failed to produce new bone formation even at 4 weeks after implantation. Calcium content of the retrieved FDPLLA/BMP discs was statistically higher than that of plain FDPLLA discs. These results suggest that FDPLLA may be an effective delivery system for BMP and that the FDPLLA/BMP disc may potentially have usefulness as a bone graft substitute.