The effect of monomer-to-powder ratio on the material properties of cranioplastic

Percutaneous vertebroplasty consists of injecting polymethylmethacrylate ce ment into the cancellous bone of vertebral bodies for the treatment of vari ous lesions of the spine, including osteoporotic compression fractures. Cli nicians practicing vertebroplasty commonly alter the mixture of monomer-to- powder recommended by the manufacturer in an effort to decrease viscosity a nd increase the working time. The purpose of the current study was to measu re the effect that varying the monomer-to-powder ratio has on the compressi ve material properties of a cement (Cranioplastic) commonly used in vertebr oplasty, Cylindrical specimens were prepared varying a monomer-to-polymer r atio of 0.40 to 1.07 mL/g and tested per the American Society for Testing a nd Materials standard F451. Specimens prepared at 0.53 mL/g, which is near the manufacturer's recommended monomer-to-polymer mixture of 0.57 mL/g, exh ibited the greatest mean values for ultimate compressive stress, yield stre ss, and elastic modulus. Specimens prepared at higher or lower ratios exhib ited diminished strength, in some cases by as much as 24%. Although alterin g the monomer-to-powder ratio affects the cement's material properties, it is as Set unknown if the decrease Is clinically significant. (Bone 25:27S-2 9S 1999) (C) 1999 by Elsevier Science Inc. All rights reserved.