Antibiotic release and antibacterial efficacy in cement spacers and cement beads impregnated with different techniques: In vitro study.

Objectives: This study aims to compare the antibiotic release and biological effectiveness of bead type and articulating spacers of different cement types with antibiotics added at alternative phases of cement preparation.

Materials and methods: Four gram vancomycin was added into two types of antibiotic-free cement (Simplex®, Biomet®) with similar viscosity and also gentamycin-containing cement (Refobacin®). Prepared specimens were used to create cement beads and articulating hip spacers, making a total of six different groups. Two alternative groups were formed by adding the Vancomycin while the cement was in dough phase. Antibiotic release and biological activity were evaluated with immunoassay techniques and agar-disk diffusion methods.

Results: All groups showed initial antibiotics surge in the first week, which was 2 to 4 times more evident in the beads group. Antibiotic release and change in release rate were significantly different between Simplex-alternative and Simplex, Biomet, Refobacin-beads, and between Biomet-spacer and Refobacin-beads groups (p<0.05). Elution of antibiotics was not different between mobile spacers prepared with conventional or alternative methods (p>0.05). Biomet cement showed larger diffusion inhibition zone in agar. There was no difference between biological activity of the bead and mobile designs of the Biomet brand (p>0.05). Inhibition zone analyses of agar and disk diffusion tests revealed significant differences between several groups (p<0.05).

Conclusion: Cement beads provide superior antibiotic release regardless of cement type or preparation method. Simplex P® cement has lower anti-bacterial efficiency than Biomet®. Different methods for cement and antibiotics mixing and addition of extra vancomycin into the commercially drug loaded cement do not have any effect on the results.