The effect of local antibiotics in treating chronic osseous Staphylococcus aureus infection

The purpose of this study was to determine if antibiotic-supplemented bone allografts (ASBA) would enhance healing and reduce infection in chronic osteomyelitis. Intramedullary injection of Staphylococcus aureus was used to create osteomyelitis in the tibia of New Zealand white rabbits. Twenty-one days postinoculation, the animals were randomly assigned to one of the following six treatment groups: 1. debridement of the infected tibia; 2. debridement + bone graft; 3. debridement + bone graft + gelatin powder; 4. debridement + bone graft + gelatin powder supplemented with antibiotics; 5. debridement + gelatin powder supplemented with antibiotics; and 6. no surgical intervention. The debrided material was cultured for identification of microorganisms. All groups received cephalothin sodium, 100 micrograms/kg subcutaneously every 12 hours for 21-days. At time of death the tibia were assessed to determine the degree of healing. Radiographs, bacterial cultures and specimens for histologic study were obtained. Qualitative grading demonstrated a significant difference between groups (P less than .001). Groups (4 and 5) receiving local antibiotic supplementation demonstrated improved healing compared with the remaining groups. However, there was no difference between groups 4 and 5. Bacteriologic culturing indicated the greatest reduction in colony-forming units of S aureus in the postsacrifice graft sites to be in groups 4 and 5. Histologic findings paralleled qualitative assessment of healing of the gross specimens. The results of this study suggest that local antibiotic supplementation of graft preparations may be useful for treatment of chronic osseous infection.