Microbiological and pharmacological tests on new antibiotic-loaded PMMA-based composites for the treatment of osteomyelitis

Local antibiotic diffusion in rabbit femurs from two new PMMA-based and nail-shaped composites, enriched with β-tricalcium phosphate (P-TCP) and BaSO4 or only with BaSO4 (P-BaSO4), and soaked in a solution of gentamicin (G) and vancomycin (V) was studied. Nails were implanted into the intramedullary cavity of healthy and osteomyelitic femurs to study the resolution of infection and to quantify the antibiotic penetration into bone by microbiological, pharmacological and histological tests. A significant progression of osteomyelitis was recorded 7 weeks after MRSA inoculation, whereas no bacteria were found in animals treated with antibiotic-loaded nails as confirmed by microbiology and histology (Smeltzer score). The release of both antibiotics from composites was high and prompt both in healthy and infected bone; the amount of V was higher than that of G in all bone samples. Antibiotics of both composites were still present in bone three weeks after nail implantation. The P-BaSO4 composite released a lower amount of antibiotics than did P-TCP. The G-V combination in vivo exerted a synergistic bactericidal effect, which was confirmed by microbiological, histological and clinical results (no infection). These new porous PMMA composites, soaked in G-V solution in the operating room, might be an effective and useful drug delivery system for osteomyelitis treatment.