Pseudoplasticity and setting properties of two-solution bone cement containing poly(methyl methacrylate) microspheres and nanospheres for kyphoplasty and vertebroplasty.

The viscosity and setting parameters of acrylic bone cements used for restoring vertebral compression fractures are critical factors in vertebroplasty and kyphoplasty procedures. Cements exhibiting lower viscosities and longer setting times are desired to overcome the difficulty of forcing the dough through small gauge needles and to reduce the risk of cementing them during surgery. However, cement extravasation is of great concern and can result when cements exhibiting lower viscosities are used. Therefore, the viscosity of cements should also be highly pseudoplastic to simultaneously facilitate flow through needles (shear-thinning) and inhibit potentially deleterious extravasation by viscosity recovery at the delivery sites. The viscosity of two-solution bone cement can be manipulated by changes in the polymer-to-monomer ratio and by the incorporation of cross-linked poly(methyl methacrylate), (PMMA), microspheres or nanospheres in the polymer phase. In this study, the effect of the addition of cross-linked PMMA particles to the linear polymer-monomer solution with particle sizes ranging from 20-100 microm (microspheres) and 300-330 nm (nanospheres) is evaluated in terms of cement rheological properties and setting behavior. The addition of cross-linked PMMA particles was observed to reduce the viscosity in comparison to the standard formulation while keeping the pseudoplastic characteristics, and to improve the setting properties by increasing curing time and reducing maximum exotherm significantly. (c) 2009 Wiley Periodicals, Inc.