[Potential of allogeneic bone grafts as antibiotic carriers : Effect of different preparation processes on efficacy].

BACKGROUND: The rising number of primary joint replacements worldwide is causing an increase of endoprosthetic revision surgery due bacterial infection. Revision surgery using non-cemented implants seems beneficial for the long-term outcome, and the use of antibiotic-impregnated bone grafts might control the infection and provide a good support for the implant. In this study, we evaluated the release of antibiotics from fresh-frozen and lyophilized allogeneic bone grafts.

METHODS: Heat-treated, lyophilized and fresh frozen cryopreserved bone chips were impregnated with gentamicin sulphate, gentamicin palmitate and vancomycin, and calcium carbonate/calcium sulphate treated with antibiotics. The efficacy of each preparation was measured by drug release tests and bacterial susceptibility using B. subtilis, S. aureus and methicillin-resistant Staphylococcus aureus.

RESULTS: The release of gentamicin from lyophilized bone was similar to the release rate from fresh frozen bone during the entire experiment. This might be related to the similar porosity and microstructure of the bone chips. The release of gentamicin from lyophilized and fresh frozen bone was high on the first and second days, then decreased and stayed at a low rate until the end of the second week.

CONCLUSION: Depending on the surgical strategy, either polymethylmethacrylate or allogeneic bone are able to deliver sufficient concentrations of gentamicin to achieve bacterial inhibition within 2 weeks after surgery. In the case of uncemented revision of joint replacements, allogeneic bone can deliver therapeutic doses of gentamicin and peak levels immediately and a fortnight after implantation.