Time and mixing technique-dependent changes in bone cement SmartSet® HV

For the past fifty years bone cements based on polymethylmethacrylate (PMMA) have been used in orthopaedic surgery for fixation of endoprostheses, especially in the cases of total hip replacement. It was shown that during this period vacuum mixing minimalizes the number of unwanted pores and thereby influences the mechanical properties of the cement. It was also discovered that later polymerization of the cement after its implantation lasts up to 6 months and changes its mechanical properties. In this study, mechanical properties (microhardness and elastic modulus measured by microindentation) of hand- and vacuum-mixed acrylic bone cement SmartSet HV® were investigated and compared after different time of cement exposition. This study points out that the measures of changes occurring with time in mechanical properties of differently mixed cement samples are equal but microhardness and elastic modulus are different and depend upon the technology of mixing.