Gentamicin Coating of Metallic Implants Reduces Implant-related Osteomyelitis in Rats

Antibiotic prophylaxis is a routine procedure in orthopedic surgery. Various local antibiotic delivery techniques are used to reduce bone- and soft tissue-related infection. The objective of this study was to evaluate the efficacy of a new biodegradable, gentamicin-loaded poly(D,L-lactide) (PDLLA) coating of orthopedic devices in preventing implant-related osteomyelitis. The medullary cavities of tibiae in 30 Sprague Dawley rats were contaminated with Staphylococcus aureus (10(3) colony forming units). Simultaneously titanium Kirschner wires, uncoated (group II), coated with PDLLA (group III), or coated with PDLLA + 10% gentamicin (group IV), were implanted. Ten animals that received phosphate-buffered saline and uncoated Kirschner wires served as controls (group I). Follow-up was 6 weeks. In weekly intervals X-rays of the tibiae were performed, blood counts were taken, and body temperature and weight were determined. After sacrifice infection was evaluated by histological and microbiological analysis. All animals of groups II and III developed microbiological, histological, and radiological signs of infection, including osseous destruction and soft tissue swelling. All animals of the control group remained sterile. Cultures of implants of group IV showed significantly reduced bacterial growth compared to cultures of groups II and III, and three implants of group IV remained sterile. Further radiological and histological signs of infection were significantly reduced in the gentamicin-coated group compared to groups II and III. No significant differences in body weight, body temperature, and blood parameters between all groups were observed. Local application of antibiotic-coated orthopedic devices containing PDLLA and 10% gentamicin significantly reduced implant-related infection in this animal model.