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Gentamicin incorporated in beads of polymethylmethacrylate has been shown capable of being released over a period of several months in concentrations sufficiently high to control most pathogens. The therapeutic efficacy of such beads has been demonstrated in a model of osteomyelitis of the femur in the dog. Good tolerance has been shown, both in the animal model and in tissue cultures. In forty-one patients with infection of either bone or soft tissue, mainly of the lower limb, the findings were similar. The concentrations in serum and urine were low, which excludes side-effects. The insertion of gentamicin-PMMA beads may prove to be a valuable new form of local antibiotic therapy.

Comparing several antibiotics and different bone cements, the mixture of Palacok R (polymethylmethacrylate, PMMA) with gentamicin proved to be the most suitable one as far as a high and sustained release of the antibiotic from the artificial resin is concerned. A antinuous leaching of gentamicin was observed for more than 5 years. w t a m i c i n proved to be stable in Palacos R for the whole period of time. The release of 12 antibiotics from Palaas R was evaluated in witro. Four other bone cements were included in this itudy as well, in order to evaluate the leaching of gentamicin from these materials. The combination Gentamicin-Palacos R (GP) showed a 2-3 fold higher and much more prolonged release than did the other mixtures. From this investigation, which also included studies of commercially available antibiotic bone cement mixtures, it is quite obvious that there exist distinct differences in the various bone cements as well as in the various antibiotics as regards their qualification for use in alloarthroplasty. Pharmacokinetic studies in patients after implantation of G P showed low gentamicin concentrations in serum (on average 1.8 pg/ml) and urine. However, in wound exudate, derived directly from the vicinity of the implanted cement, gentamicin concentrations up to 150 pg/ml were observed. Also in tissue samples from the vicinity of the implant, high concentrations were measurable for a long period of time (up to 5+ years).

The in vitro release of vancomycin, teicoplanin, gentamicin and clindamycin from biodegradable calcium sulphate (CaSO(4)) carrier beads is described. All antibiotics showed prolonged release from the carrier beads, which was elevated during the first 24 h, with peak levels exceeding 2500 microg/bead. Doubling the antibiotic load of the beads revealed a more prolonged elution and a two-fold increase in antibiotic release. Local carrier-associated antibiotic treatment with CaSO(4) beads may prove to be effective in the management of chronic bone infections.