New model for chronic osteomyelitis with Staphylococcus aureus in sheep.

The purpose of this study was to develop a large animal model for chronic osteomyelitis, suitable for toxicologic research and therapeutic intervention studies. Osteomyelitis was induced in 52 healthy adult Texel sheep by injecting a sclerosing agent and a hemolytic strain of Staphylococcus aureus into the proximal tibial marrow cavity. Evaluation was done by clinical, radiologic, bacteriologic, and histologic parameters for 3 months. Clinical signs of infection consisted of localized soft tissue swelling, pain during the acute phase, and limping in all sheep. Radiologic features were moderate to extensive periosteal reaction, cortical lysis, mild to extensive new bone formation, and frequent development of sequestra limited to the proximal part of the tibia. Cultures were positive for the same strain of Staphylococcus aureus in all but one sheep. Histology showed chronic active inflammation, osteolysis, new woven bone formation, debris, clusters of bacteria, and surrounding granulation tissue. It was necessary to administer a single prophylactic dose of antibiotics 1 hour after surgery to prevent fatal sepsis. It was concluded that sheep are a suitable model for chronic osteomyelitis.