Efficacy of Cefazolin Versus Vancomycin Antibiotic Cement Spacers.

OBJECTIVE: Cefazolin is a heat-labile antibiotic that is not usually added to polymethylmethacrylate (PMMA) cement spacers because it is believed to be inactivated by the high polymerization temperatures. The purpose of this study was to compare cefazolin versus vancomycin high-dose antibiotic cement spacers.

METHODS: High-dose antibiotic PMMA spacers with either cefazolin or vancomycin were fabricated. Setting time, compressive strength, and compression modulus of spacers were measured. Spacers were emerged in saline, and the eluent was tested on days 1, 2, 3, 7, 14, and 30 to determine the zone of inhibition of methicillin-sensitive Staphylococcus aureus and estimate the cumulative antibiotic released.

RESULTS: Cefazolin, compared with vancomycin-loaded spacers, had significantly shorter setting time [mean difference (MD) -1.8 minutes, 95% confidence interval (CI), -0.6 to -3.0], greater compressive strength (MD 20.1 megapascal, CI, 15.8 to 24.5), and compression modulus (MD 0.15 megapascal, CI, 0.06 to 0.23). The zone of inhibition of eluent from PMMA-C spacers was significantly greater than PMMA-V spacers at all time points, an average of 11.7 ± 0.8 mm greater across time points. The estimated cumulative antibiotic released from cefazolin spacers was significantly greater at all time points ( P < 0.0001).

CONCLUSIONS: Cefazolin was not inactivated by PMMA polymerization and resulted in spacers with superior antimicrobial and biomechanical properties than those made with vancomycin, suggesting that cefazolin could play a role in the treatment of infected bone defects with high-dose antibiotic PMMA spacers.