Experimental study of impregnation conditions for sustained antimicrobial activity of the original osteoplastic material based on cancellous bone allograft

Introduction Local antibiotic therapy is used to prevent and treat periprosthetic joint infection, but the available antibiotic delivery systems have some limitations. The objective was to determine optimal parameters of pressure, exposure time and type of solvent to ensure prolonged elution of vancomycin from the original osteosubstituting material based on cancellous allograft bone using an in vitro experiment. Material and methods Seven impregnation techniques with different combinations of parameters were examined including pressure: from atmospheric to reduced (7–10 hPa), time: from 5 minutes to 24 hours, solvent (distilled water, 50 % ethanol solution, a combination of 50 % ethanol and 5 % polyvinylpyrrolidone (PVP)). The efficacy was assessed by changes in the diameter of the S. aureus ATCC 43300 inhibition zone using the bacteriological method and the dynamics of vancomycin concentration in the eluate and high‑performance liquid chromatography (HPLC). Statistical analysis was performed using the ANOVA method, Tukey's post-hoc test, Spearman's rank correlation and calculation of the area under the pharmacokinetic curve. Results The best efficiency was demonstrated by the method employing reduced pressure, 60-minute exposure and an alcohol solution with PVP, which provided prolonged release of vancomycin for 14 days with the maximum area under the elution curve (301364.70) and a high correlation between the concentration of the antibiotic and the growth inhibition zone (r = 0.908, p < 0.001). The pressure was found to be the most significant factor (F = 19.9916, p < 0.0001), followed by solvent type (F = 7.7485, p = 0.0006) and impregnation time (F = 6.8084, p = 0.0014). Discussion The technique with use of reduced pressure and an alcohol solution with PVP provides prolonged release of vancomycin for 14 days as opposed to conventional local antibiotic therapy with limited effectiveness of 3 to 7 days. The advantage of the approach includes uniform elution kinetics compared to polymethyl methacrylate and biodegradable carriers, which demonstrate a sharp initial release of the antibiotic. The complementary use of the microbiological method and HPLC indicated antimicrobial activity of vancomycin maintained after impregnation being essential for the therapeutic effect. Conclusion It has been experimentally established that reduced pressure (7–10 hPa), an exposure time of 60 min and the use of 50 % ethanol with 5 % PVP as a solvent appeared to be the optimal parameters for ensuring prolonged elution of vancomycin from an osteosubstituting material based on cancellous allograft bone.