Mixing does not improve mechanical properties of all bone cements. Manual and centrifugation-vacuum mixing compared for 10 cement brands.

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.