Is there any difference between vacuum mixing systems in reducing bone cement porosity?

Six vacuum mixing systems, Cemvac, Merck, Mitvac, Optivac, Osteobond, and Stryker, were tested using prechilled Palacos R bone cement to investigate the reduction of porosity compared to mixing at atmospheric pressure. In addition the Optivac, Osteobond, and Stryker were tested using Simplex P bone cement to find out if they were effective in reducing the porosity of a middle viscosity bone cement. All vacuum mixing systems reduced the number of macropores (> 1 mm) and micropores (0.1 mm < voids < 1 mm) and increased the density of both Palacos R and Simplex P. But only the Optivac, Stryker, and Merck systems reduced the area percentage of macropores with more than 50% compared to the control. When using Simplex P bone cement, all three mixing systems tested reduced the numbers and the area percentage of macropores compared to the control. The results show that vacuum mixing is effective in reducing the porosity in both a high viscosity cement such as Palacos R and a middle viscosity cement such as Simplex P. Not all systems tested were effective in reducing the number and size of large voids.