A novel spinal implant infection model in rabbits

Study Design. A new spinal implant model was designed to study device-cente red infection with methicillin- resistant Staphylococcus aureus in multiple noncontiguous surgical sites in the lumbar spine region of a rabbit. Objective. To develop a multiple-site spinal implant device-centered infect ion model in rabbits. Summary of Background Data. Results in many recent studies show that postop erative wound infection after spinal implant surgery and the increase in an tibiotic-resistant bacteria are a concern. Anti-infection strategies must b e tested in relevant animal models that will lead to appropriate clinical s tudies. Methods. Eight anesthetized New Zealand White rab bits underwent completely isolated partial laminectomy and subsequent stainless steel Kirschner wire implantation directly into the transverse processes of vertebrae T13, L3, and L6. The middle sites (L3) were used as sterile; control sites, and the outer sites (T13, L6) were challenged with different amounts of methicillin -resistant Staphylococcus aureus, Rabbits were killed after 7 days, and bio psies were performed to provide evidence for device-centrered-infection. Ba cterial growth on the implant surfaces and in surrounding tissues and bone was assayed. Results. Overall device-centered infection was established after 7 days in 100% of the sites challenged with 10(3) colony-forming units methicillin-re sistant Staphylococcus aureus or higher. No infection was seen in any of th e control sites located between infected vertebrae. Multiple blood and live r samples showed that the separate localized infections did not become syst emic after 7 days. Conclusions. This new animal model demonstrates that multiple biomaterial i mplants can be evaluated in the same animal and provides a technique for in vestigating postoperative device-centered infection of the spine. In infect ion was demonstrated in noncontiguous lumbar sites of the spine, whereas ad jacent control sites remained sterile. Because there was no cross contamina tion or systemic spread of the infection, multiple anti-infection strategie s or implant materials can now be tested for efficacy in a single animal to combat dramatic and costly postoperative implant infections.