“The vacuum mixing system produces set specimens of less than 1% porosity that have significant improvements over specimens prepared with conventional mixing in the mechanical properties of tensile and compressive strength and uniaxial tensile fatigue life. Hence, a much stronger cement can be available in surgery without any change in original chemical composition.”
“Independent study of these issues by Lidgren et al., who used a vacuum mixing method, also demonstrated the reduction in porosity and improvement in materials properties. They compared hand mixing, mixing with vibration, and vacuum mixing, using an experimental low-viscosity cement formulation and Refobacin-Palacos, a high viscosity cement. For both cements, they found a significant increase in compressive strength, flexural strength, and elastic modulus for vacuum mixing, compared with the hand mixing and vibration techniques.
With both our technique and that of Lidgren et al., there is a significant improvement in the material properties of the cement being used. The elimination of boids in the testing specimens effectively increases the amount of material in the cross-section subjected to testing.”
Reference:Richard L. Wixson, MD, Eugene P. Lautenschlager, PhD, and Michael A. Novak, DDS.
“Acrylic bone cement mixed manually under operating room conditions is porous and contains small and large voids. Fatigue fractures were shown to most likely occur at the site of the largest voids, and the porosity of acrylic cement tends to dictate its mechanical performance.”
“Vacuum mixing with a rotating axis gave the lowest values for both unmixed powder and number of voids/cm2. The principle of a rotating-axis design resembles that of a blender mixer. The position of the mixing blades constantly changes during mixing as the axis of rotation moves within the outlined circular tract. This may prevent the accumulation of powder at any point, thus providing a better blend within the mix.”
Reference:N. M. G. Kurdy, J. P. Hodgkinson, R. Haynes
“Vacuum mixing of PMMA bone cement is advocated to reduce voids and porosity within the cement mantle, which are suspected to contribute to crack development and prosthesis failure or loosening. The vacuum mixing devices are connected to specific suction units and are thus also expected to minimize exposure to MMA monomer fumes evaporating during the mixing procedure. MMA is a toxic, highly volatile organic solvent. Cytotoxic effects on human fibroblast in culture media have been described and attributed to MMA. Exposure to MMA vapors may have irritating effects on mucous membranes of the respiratory tract and the eyes. Direct contact with OMMA bone cement may lead to toxic dermatitis, whereas exposure over several years has been suggested to be a cause of toxic encephalopathy. ”
Reference: Ulf J. Schlegel, Michael Sturm, Volker Ewerbeck and Steffen J. Breusch.
