In vitro elution of tobramycin and vancomycin polymethylmethacrylate beads and spacers from Simplex and Palacos

In vitro studies of antibiotic elution from polymethylmethacrylate cement comparing Simplex (Howmedica, Rutherford, NJ) with Palacos brands (Richards, Memphis, TN) have shown variable results. This study compares the elution of tobramycin and vancomycin from Simplex and Palacos beads and spacers. Six-millimeter beads and spacers were incubated in phosphate-buffered saline, and the solution was sampled and changed daily until the concentration of antibiotic fell below the minimum inhibitory concentration (MIC) for Staphylococcus aureus. In all groups, the Palacos PMMA beads and spacers showed elution at higher levels and remained above the MIC longer than did the Simplex PMMA beads. Tobramycin had superior elution to vancomycin in all groups. This in vitro study shows that Palacos PMMA has superior elution properties to Simplex PMMA in tobramycin and vancomycin beads and spacers.