In vitro measurement of the time-related efficacy of gentamicin sulfate release from bone cements

BACKGROUND: The aim of the present study was to establish an in vitro microbiologic monitoring system which measures the dynamics of antibiotic release from acrylic bone cement and its antibacterial efficacy. METHODS: Palacos R and Orthofix R cements containing gentamicin sulfate were tested. The in vitro elution dynamics was analyzed by plate diffusion method during a 1-year period after mixing. High but rapidly decreasing antibiotic levels were detected within the 1st week, resulting in an almost steadily low concentration by the end of the 1st month. After 1 year, it was still possible to demonstrate the inhibitory effect of the drug from both cements. Comparison of the time-related release between the antibiotics failed to find any statistically significant differences. CONCLUSION: The method described is a useful and reproducible technique for the in vitro measurement of the inhibitory activity of antibiotic released from bone cements.