Elution Characteristics of Vancomycin, Gentamicin, and Vancomycin/Gentamicin Combination from Calcium Phosphate Cement

The antibiotic elution profiles from calcium phosphate cement (CPC) used for treating infection sites after total joint arthroplasty vary depending on the type and number of impregnated antibiotics. The purpose of this study was to develop a method for efficiently eluting vancomycin hydrochloride (VCM) and gentamicin sulfate (GM) from CPC. Examination of the antibiotic elution profiles of CPC impregnated with either VCM (CPC/V) or GM (CPC/G) or both (CPC/VG) revealed that the early elution of VCM from CPC/VG was impaired compared to CPC/V. However, the elution of GM from CPC/VG was similar or higher compared to CPC/G. Scanning electron microscopy showed that the pore structure of CPC markedly differed depending on the type and number of antibiotics present. The pore size of CPC/VG was smaller compared to CPC/V but was larger compared to CPC/G. Thus, the inhibition of the early elution of VCM, which is a larger molecule than GM, was attributed to the decreased pore size of CPC/VG. These findings suggest that when dual treatment with VCM and GM is required for infection following total joint arthroplasty, each antibiotic should be individually impregnated into CPC to maximize the elution efficiency of VCM