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

Abstract

Purpose: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

Keywords: antibacterial activity; antibiotic impregnated bone cement; elution; mechanical characteristic; toxicity.

Figure 1

The elution profiles (mean ± SD) of gentamicin (A) and vancomycin (B) over a 28-day period.

Figure 2

Compressive strength (A) and compressive modulus (B) of tested cement. The dashed line on the left represents the lower limit of 70 MPa established by ISO 5833.

Figure 3

The accumulated gentamicin (circle) and vancomycin (square) released from cement tested as a function of porosity. The dashed cycles represent the four pairs of data generated from G1V1 and G2V2. The solid and dashed lines show the trend between porosity and accumulated antibiotic elution.

Figure 4

Antimicrobial activity of cement tested in this study. The pie chart represents these three bacteria that were the most commonly found in periprosthetic joint infection. Different colors represent different levels of bacterial growth as illustrated in the figure. Abbreviations: S. aureus: Staphylococcus aureus ATCC 43300; E. feacalis: Enterococcus faecalis ATCC 29212; E. coli: Escherichia coli ATCC 35218.