Study Of Modified PMMA Bone Cement With Mineralized Collagen

Polymethyl methacrylate(PMMA) bone cement is the most commonly used in orthopedic clinic surgery for bonding and filling. There had been 30 years’ history in the application of percutaneous vertebroplasty(PVP), the safety, effectiveness and long-term curative effect have been verified with large number of theoretical studies and clinical practices. However, there still exist the problems that high elastic modulus and bad biocompatibility which may cause some complications in clinic, such as adjacent vertebral fracture and set PMMA bone cement may be loosened or even get off from the vertebral body as the bioinert PMMA bone cement cannot form osteointegration with autologous bone tissuein the application of PVP. In this study, we used mineralized collagen(MC) particles with great osteogenic activity to develop a new composite PMMA bone cement and evaluate the effect of modification in mechanical and biological properties in vitro. Through composition of MC particles, the compressive modulus of the set cement was significantly reduced compared to pure PMMA bone cement and commercially available products, while the compressive strength maintained well. Therefore, the change reduces wear of bone tissue surrounding implant part and incidence rate of secondary fracture of adjacent vertebral body. Cell experiments indicate that incorporation of MC particles improved biocompatibility of set PMMA bone cement, and exhibited better cell attachment and proliferation. Also show better osteogenic differentiation of human bone mesenchymal stem cells on modified PMMA bone cement. After culturing for 21 days, activity of alkaline phosphatase on modified group showed more than two times higher than that of pure PMMA cement. Results of RT-PCR showed expression of osteogenic related genes had a significant increase at RNA level in the group of modified group.In animal experimentation, after implanting into animals for a period of time, we can see the mineralized collagen particles on the surface of modified PMMA bone cement were degraded andabsorbed gradually and form pore structure, at same time, guide the new bone tissue grow into the pores and form stable autologous bone-implant interface. The results show that the modified material has good bone integration ability, reduce the risk of bone cement loose or fall off, improve the safety and long-term effects of PMMA bone cement. In addition, using the mineralized collagen particles in PVP does not affect the syringeability, also have little effect to the operation and accord with the doctor’s operation habit in clinical.