Local Application of Free Antibiotic Powder in the Treatment of Osteomyelitis in a Rat Model

To date, several strategies have been developed to provide local antibiotic therapy in the treatment of osteomyelitis, such as antibiotic-loaded bone cement, antibiotic-impregnated collagen sponges, polymethylmethacrylate beads, antibiotic-loaded bone graft, antibiotic-loaded synthetic bone substitutes, and antibiotic-coated implants. The optimum carrier for local antibiotic therapy has not been identified. Tibial osteomyelitis using methicillin-sensitive Staphylococcus aureus was created in a rat model. Rats were assigned to 3 treatment groups: group A, systemic antibiotics only; group B, systemic antibiotics plus surgical debridement; and group C, systemic antibiotics, surgical debridement, and application of cefazolin. Infection was assessed using gross tissue analysis, radiographs, quantitative bacteriology, and histopathology. One-half of the rat tibias were randomly chosen for histological evaluation and the other half were used for microbiological analysis. Radiographs were reviewed and graded by 4 blinded board-certified radiologists. Histology slides were reviewed and graded by a blinded board-certified pathologist. Gross tissue analysis of treatment groups B and C demonstrated a statistically significant improvement in soft tissue infection clearance compared with group A (P<.05). No difference was found between treatment groups B and C. No significant difference existed in gross tissue, radiographic, microbiologic, or histopathologic analyses among the 3 groups for osteomyelitis. The results of this study demonstrated that the local application of free antibiotic powder is as effective as local debridement alone in treating soft tissue infection associated with tibial osteomyelitis in a rat model.