Direct and interactive effects of three variables on properties of PMMA bone cement for vertebral body augmentation

PMMA bone cements are widely used for vertebral body augmentation procedures vertebroplasty and balloon kyphoplasty. Although there are studies in the literature on the direct effects of relevant variables on the properties of these cements, there are none on the interactive effects. In the present work, such a study was performed on both types of effects, with the variables being the concentration of initiator (benzoyl peroxide), the concentration of crosslinker (ethylene glycol dimethacrylate), and the liquid-to-powder ratio used in preparing the cement; and the properties being the compressive strength, the compressive modulus, the doughing time, the setting time, and the maximum polymerization temperature. Two additional properties obtained from the viscosity-versus-time curves, namely the time at the onset of curing, and the critical curing rate were also studied. Significant interactive effects between the amount of crosslinker and the amount of radical initiator were found to affect the doughing time and the critical curing rate. These effects were explained in terms of the reaction kinetics. It was concluded that interactive effects may exist and should be taken into account when designing bone cement formulations.