Rheological properties of acrylic bone cement during curing and the role of the size of the powder particles.

A dynamic compressive rheometric technique was used to determine the true or complex viscosity (eta*) of three poly (methyl methacrylate), PMMA-based bone cement formulations (one commercially available and two experimental), as a function of the time that elapsed from commencement of hand mixing of the cement constituents (t). For each cement, two rheological parameters [namely, the time of onset of cure (t(ons)) and the critical cure rate (CCR), which is herein defined as the complex viscosity rate computed at t(ons)] were determined from the eta*-t data. For each cement, particle analysis was used to obtain the powder particle size distribution, from which the following parameters were obtained: (a) the overall mean particle diameter D(m), and (b) the relative amounts of small-sized PMMA beads (mean diameter d between 0 and 40 mum) (alpha) and large-sized PMMA beads (d > 75 mum) (beta). It is seen that the key particle parameter is not D(m) per se but alpha and beta. Thus, the highest values of t(ons) and CCR were obtained from a cement with the highest values of alpha and beta. An explanation for these trends is given, and two areas for further research work in this field are outlined. Copyright 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 191--199, 2002; DOI 10.1002/jbm.10127