Improved bone ingrowth of tricalcium phosphate filled Poly(methyl methacrylate) (PMMA) bone cements in vivo

The cement augmentation technique using poly(methyl methacrylate) (PMMA) is considered to be the most effective method for fixation of osteoporotic fracture because of its outstanding mechanical properties. However, the low bio-degradation of PMMA, which hinders bone ingrowth, limits it potential for a broad range of applications. Previous studies have shown blending beta-tricalcium phosphate (beta-TCP) with PMMA was able to improve the osteoconduction while the material still suffered poor mechanical properties due to the poor compatibility between two components. In this study, we explored the use of hydroxyethyl methacrylate (HEMA) as a compatibilizer for improving the affinity of TCP/PMMA blends system. The resultant TCP/HEMA/PMMA(THP) composite cements exhibited similar setting properties to PMMA cement but much better mechanical properties than composite systems without HEMA as a compatibilizer. No cytotoxicity or hemolysis was observed in the THP bone cement system by biochemical assays. Bone ingrowth was significantly improved at 12 weeks. The reinforced pull-out strength of screws was observed at 4, 8, 12 weeks through in vivo studies performed on rabbit femurs. The THP system, as an injectable bone cement material, shows great potential for use in the cement augmentation technique.