Two-solution bone cements with cross-linked micro and nano-particles for vertebral fracture applications: Effects of zirconium dioxide content on the material and setting properties

The application of bone cements for the treatment of vertebral compression fracture requires radiopaque materials for adequate visualization of the flow under fluoroscopy. Besides high radiopacity, it is desirable for the cement to have relatively low viscosity, high compressive strength and appropriate curing parameters. In this study, the properties of novel two-solution bone cements composed of cross-linked poly (methyl methacrylate) PMMA microspheres or nanospheres added to the linear polymer phase were assessed for formulations with increasing concentrations of zirconium dioxide (ZrO₂). The addition of a cross-linked phase in the standard two-solution formulation (TSBC) was observed to improve the material properties by increasing setting time and decreasing maximum polymerization temperatures and decreasing the initial viscosity in comparison to the standard cement. The properties of three formulations (TSBC, modified two-solution containing cross-linked PMMA microspheres, and nanospheres) were measured for cements prepared at 0%, 5%, 20%, and 30% ZrO₂ and compared to KyphX. Cements prepared with cross-linked particles exhibited significantly higher compressive strength than the standard-two solution cement and KyphX at increasing radiopacifier concentrations. Furthermore, cement viscosity was increased by the addition of increasing concentrations of ZrO₂ in the modified two-solution cements, whereas the maximum polymerization exotherm and setting time of these materials were decreased. This study indicates that the addition of high concentrations of ZrO₂ significantly affects the properties of two-solution cements acting as a reinforcing phase when cross-linked spheres are added. These materials were observed to be suitable for vertebroplasty applications.