High dose of vancomycin plus gentamicin incorporated acrylic bone cement decreased the elution of vancomycin

Low doses of vancomycin and gentamicin were commonly incorporated into acrylic bone cement (antibiotic-impregnated bone cement, AIBC) during revision arthroplasty. Previous studies showed that only a very small amount of antibiotics could be eluted from AIBC. Given the fact that a high dose of antibiotic would elute high concentration of antibiotic, this study investigated the influence of a high dose of dual-antibiotic loading on the properties of cement.

A total of 8 groups of AIBC containing either gentamicin or vancomycin or both with different amounts of antibiotics (1 g, 2 g and 4 g) were tested on material properties, elution profiles, antibacterial activity and cytological toxicity.

A high dose of gentamicin and vancomycin AIBC (with 2 g gentamicin and 2 g vancomycin loaded) regiment showed acceptable compressive strength of 74.25±0.72 MPa. No cytotoxicity or antibacterial activity reduction was observed in any group tested in this study. The elution profiles indicated that incorporating 2 g vancomycin resulted in 4.77% (1049.57±3.74 μg) released after 28 days. However, after 2 g gentamicin was added, the vancomycin released was significantly reduced to 2.42% (532.24±1.77 μg) (p<0.001), approximately 50% reduction. No significant influence of vancomycin on gentamicin was observed.

These findings suggest that the addition of 2 g vancomycin and 2 g gentamicin into acrylic bone cement was preferred while considering this dual-antibiotic AIBC regiment with acceptably material properties and effective antibacterial activity. However, special attention should be drawn to the reduction of vancomycin elution when incorporated with gentamicin.