Comparison of elution characteristics and compressive strength of biantibiotic-loaded PMMA bone cement for spacers: CopalD Spacem with Gentamicin and Vancomycin versus PalacosD R+G with Vancomycin

Abstract

Purpose. Copal spacem is a new PMMA bone cement for fabricating spacers. This study compares elution of gentamicin, elution of vancomycin, and compressive strength of Copal spacem and of Palacos R+G at different vancomycin loadings in the powder of the cements. We hypothesized that antibiotic elution of Copal spacem is superior at comparable compressive strength. Methods. Compression test specimens were fabricated using Copal spacem manually loaded with 0.5 g gentamicin and additionally 2 g, 4 g, and 6 g of vancomycin per 40 g of cement powder (COP specimens) and using 0.5 g gentamicin premixed Palacos R+G manually loaded with 2 g, 4 g, and 6 g of vancomycin per 40 g of cement powder (PAL specimens). These specimens were used for determination of gentamicin and vancomycin elution (in fetal calf serum, at 22∘C) and for determination of compressive strength both prior and following the elution tests. Results. Cumulative gentamicin concentrations (p < 0.005) and gentamicin concentration after 28 days (p ≤ 0.043) were significantly lower for COP specimens compared to PAL specimens. Cumulative vancomycin concentrations were significantly higher (p ≤ 0.043) for COP specimens after the second day. Vancomycin concentrations after 28 days were not significantly higher for the Copal specimens loaded with 2 g and 4 g of vancomycin. Compressive strength was not significantly different between COP specimens and PAL specimens before elution tests. Compressive strength after the elution tests was significantly lower (p = 0.005) for COP specimens loaded with 2 g of vancomycin. Conclusion. We could not demonstrate consistent superior antibiotic elution from Copal spacem compared to Palacos R+G for fabricating gentamicin and vancomycin loaded spacers. The results do not favor Copal spacem over Palacos R+G for the use as a gentamicin and vancomycin biantibiotic-loaded spacer.