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Selected Publication:
Schmidt, P.
Investigations Towards Antimicrobial Properties of Endoprosthetic Bone Cement
Humanmedizin; [ Diplomarbeit ] Graz Medical University; 2018. pp. 70
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- Authors Med Uni Graz:
- Advisor:
- Kühn Klaus-Dieter
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- Abstract:
- Abstract Background: Hip replacement surgeries are increasing in all first world countries and in parallel also the number of periprosthetic joint infections (PJI) is increasing. Although these infections can be caused by a variety of microorganisms, the most common pathogens belong to the genus Staphylococci. Periprosthetic joint infections can result in serious complications. Therefore, different therapy and prophylaxis strategies exist with the most promising being the ’two-stage-exchange’, which consists of two surgical interventions and the use of an intermediary poly(methyl methacrylate) (PMMA) spacer loaded with antimicrobial agents (e.g. antibiotics). Due to the diversity of the causative pathogens in PJI, the problems of side effects in patients and the increasing antimicrobial resistances in bacteria, the choice of the most suitable antimicrobial agent(s) is of utmost importance. Since there are different types of PMMA and bone cements being used in surgeries around the world, it seems crucial to compare the agent releasing properties of the different bone cement-antibiotic combinations. Hypothesis: We hypothesized that the effects of different antibiotic-loaded bone cements on Staphylococcus species might be quite different. Furthermore, we predicted that magnesium monoperoxyphthalate hexahydrate (MMPP) might be able to replace antibiotics as an anti-infective agent in bone cements. Methods: Firstly, we generated molds of PMMA mixed with MMPP and incubated these in phosphate buffer. The supernatants (eluates) were then tested in vitro employing inhibition zone assays (’Hemmhoftests’) against common PJI pathogens. In a second experiment we prepared antibiotic-loaded PMMA molds, incubated them in buffer and evaluated the effectiveness of the various eluates we obtained over a period of 42 days against Staphylococcus species applying the Hemmhoftest. The results were compared and statistically evaluated. Results: Preliminary experiments with eluates obtained from MMPP-loaded molds and with different concentrations of MMPP in buffer showed that, using concentrations of MMPP in PMMA that do not sabotage the needed firmness and stability of the molds, there was no antimicrobial effect visible in the Hemmhoftests. The antibiotic-loaded molds showed very different results in these evaluations, ranging from high bactericidal properties during the whole test period to rapidly decreasing efficacies in both Staphylococcus aureus and Staphylococcus epidermidis. Conclusions: Based on these results, MMPP appears not to be a suitable replacement for antibiotics in bone cement. Interestingly, there exist notable differences between the elution properties and antimicrobial efficacies of the various bone cements, depending to a high degree on the mix and structure of the bone cements and of course on the specific antibiotics and antibiotic combinations used. These differences in performance of the various molds characterized in this study should be taken into account when choosing the appropriate therapeutic strategy.