Mixing does not improve mechanical properties of all bone cements

Contemporary mixing methods-centrifugation, vacuum mixing with or without precompression-were compared with manual mixing by testing strength characteristics in accordance with a proposed revision of the international standard for bone cements as applied to 10 cement brands. Simplex® brands and low-viscosity cements were the strongest, and were not improved by any of the vacuum-mixing procedures. Centrifuging was found unsuitable for low-viscosity cements. Without attaining the strength of the former, the cements best suited for auxiliary mixing methods were CMW-1 ® and Palacos ® brands, which improved 6-11 percent by either of the methods. The Sterivac® system was generally found unacceptable, because about 20 percent of a cement package was retained in the mixing gear, and the application of precompression had no additional effect on compressive and bending strengths.