Acrylic antibiotic-loaded bone cement: a basic study

Objective: The aim of this study was to evaluate the efficacy of antibiotic-loaded bone cement in controlling local infection and in regard to its physical characteristics, elastic modulus, and tensile strength in-vitro. Methods: Acrylic bone cement, based on polymethylmethacrylate (PMMA) was mixed with the powder form of three antibiotics, i.e., gentamicin, tobramycin, and cefuroxime with different doses below 2gr per 40gr of cement powder; thereafter, liquid monomer was added to process the cement. Sensitivity to common clinical isolates was assessed by counting the inhibition zone of each ALBC disc in cultured strains. Elution with normal saline was performed to evaluate the effects on ALBC disks and their antimicrobial efficiency. Cement structure, tensile strength, and elastic modulus were assessed by biomechanical tests to understand the characteristics of ALBCs after loading antibiotics with different doses and two methods of vacuum and manual mixing. Results: Gentamicin, tobramycin, and cefuroxime reduced bacterial growth significantly with doses more than 1gr of antibiotics in 40gr of the cement. Cefuroxime was less efficient than the other two antibiotics in controlling pseudomonas. Elution with normal saline has not affected antibacterial results, significantly. All the 3 antibiotics had the same pattern of physical characteristics while loaded in bone cement. Gross structure of ALBCs with different doses of the three antibiotics was the same as non-ALBC and the elasticity or strength did not decline after loading antibiotics. The elastic modulus of ALBC was increased by boosting the doses of antibiotics; however, doses of 1gr to 1.5gr were the optimal doses in this regard. The tensile strength of ALBC was increased by doses of 1gr to 1.5gr of antibiotics; however, below and above these doses, the strength was decreased, but it did not exceed the basic strength of non-ALBC. Vacuum mixing method increased strength and elasticity more than manual one, remarkably. Conclusion: Optimal protective effects of ALBCs against infection could be seen with mixing doses of about 1gr to 1.5gr of antibiotics in 40gr of acrylic bone cements by vacuum method, while optimal elastic modulus and tensile strength could be achieved at the same doses.