RESUMEN
BACKGROUND: Polymethylmethacrylate (PMMA) cement has been used for fixation of joint replacements for more than 50 years and cement augmentation of vertebrae has become a popular procedure since the first description in 1987. New cements have now been developed which are better suited to the requirements of minimally invasive application techniques for vertebral bodies. The combination of good mechanical properties and biocompatibility is the concern of present research. This study compared the features of a polymer-bioglass cement with a calcium phosphate cement used for vertebral augmentation. METHODS: The human osteoblast-like cell culture MG63 was used to study the polymer-glass ceramic cement Cortoss® and the hydroxyapatite cement Kyphos®. Every 24 h for 5-6 days a defined volume of the culture medium was harvested in the presence of the bone cements and added to 16 cell cultures for each time period. The viability of cells was determined photometrically at 550 nm with the MTT assay and cell morphology was studied using light and electron microscopy. RESULTS: In the presence of the calcium phosphate cement an early and small reduction of cell activity was found compared with the controls. At the end of 1 week the viability parameter improved nearly reaching the control level. Electron microscopy showed crystals with a 3-dimensional shape. The cell cultures with Cortoss® showed no cellular activity and the microscopic examinations were negative. This effect was not different at days 1-5 after polymerization of the cement. CONCLUSIONS: The calcium phosphate cement studied showed a good biocompatibility and allowed morphological signs of apatite formation. At least within the first 5 days the polymer-glass ceramic cement showed a reasonable cytotoxic effect. There was no sign of recovery of cell function within that period. The biocompatibility of the polymer-glass ceramic cement appeared significantly worse compared with the calcium phosphate cement. An ideal composition of biomechanical properties and biocompatibility has not been achieved so far.