Preparation Of Biodegradable And Bioactive Microspheres Embedded PMMA Composite Bone Cements

Poly(methyl methacrylate)(PMMA)bone cement has been primarily used as a grouting agent in total joint replacement surgery for more than 50 years.This material is widely used in more than 75 000 vertebroplasty and kyphoplasty surgeries annually,and more than 700 000 knee and hip-replacement surgeries in the medicare population in the United States.Some new type bone cement such as calcium phosphate cement and calcium sulfate cement have been developed more than 30 years,but considering their bad inject performance and mechanical properties,PMMA bone cement remain the most widely used injectable material in total joint arthroplasty,vertebroplasty and kyphoplasty.However,there are also some disadvantages of PMMA bone cement limited its application in clinical.Large number of cases confirmed that loosening and shifting of bone cement is an important cause of surgical failure.The hydrophobic and biologically inactive cement interface result in cement-bone interfaces unstable.Moreover,PMMA bone cements have the disadvantage of high elastic modulus,which results in stress shielding and includes secondary fractures of the adjacent vertebral bodies.Combining these we propose to incorporate fully degradable spherical biological material into bone cement,biological material will be slowly degraded in the body and produce cavity.The bone tissue can be produced into the bone cement along the cavity.Finally,the bone cement and bone could intermesh with each other.First,we prepared we incorporated silk fibroin(SF)and calcium phosphate(TCP)composite microspheres into PMMA bone cement.SF-TCP microspheres are prepared by electrostatic spraying method.By SEM observation,we can find 300-500 micron diameter microspheres,and the microspheres can be uniformly distributed in PMMA bone cement.Porous PMMA bone cement can be obtained after degradation,and the pores were interconnected,which demonstrated the feasibility of this vision.Mechanical properties of bone cement has been tested,the mechanical strength of 10%,15%,20%microspheres group were61 ± 5,40 ± 3.5,35 ± 5 MPa.Adding low strength microspheres can significantly reduce the mechanical strength of bone cement.The second part of this experiment used a larger mechanical strength magnesium beads as biodegradable porogens.The main limitation to the application of magnesium as medical implant materials is their rapid corrosion behavior.To delay the degradation of Mg beads,we also coating HA layer on Mg beads,and the cement consisted of PMMA and HA coated Mg beads was evaluated too.The effect of incorporation Mg beads and HA-Mg beads to PMMA bone cement was evaluated in terms of mechanical performance,curing parameters,in vitro and in vivo behavior.In this study,we incorporated degradable and bioactive SF-TCP microspheres and Mg beads into PMMA bone cement to prepare partially degradable composite cements.The microstructure of this bone cement can promote new bone tissue growth,and the added active material can promote new bone formation and strengthen bone and bone cement interface.