Delayed local treatment of rabbit tibial fractures with biodegradable cefazolin microspheres

The prevention of infection is a primary objective in the treatment of open fractures. The objective of this study was to compare the efficacy of biodegradable, poly (DL-lactide-co-glycolide) cefazolin microspheres and free cefazolin powder in Staphylococcus aureus contaminated rabbit tibial fractures when treatment was delayed for 2 hours. Fractures were produced in the tibia of rabbits, inoculated with Staphylococcus aureus, and 2 hours later treated by either direct local application of cefazolin microspheres or an equivalent dose of free cefazolin powder. Control animals did not receive antibiotic therapy. The fractures then were stabilized with a bone plate, and the animals were observed for 8 weeks. Local antibiotic therapy with biodegradable cefazolin microspheres prevented the establishment of infection in all animals, and cultures of the tibiae were sterile in all cases. In contrast, clinical evidence of infection developed in 50% of the rabbits that had been treated with free cefazolin powder and 71% of the control animals. Staphylococcus aureus was recovered from the tibiae of 75% and 100% of these animals, respectively. The results of this study suggest that local antibiotic therapy with biodegradable, controlled release cefazolin microspheres may be useful for the management of open fractures in humans, even when treatment is delayed for several hours after bacterial contamination.