Experimental osteonecrosis induced by a combination of low-dose lipopolysaccharide and high-dose methylprednisolone in rabbits

The pathogenetic mechanisms involved in steroid-induced osteonecrosis are poorly understood. Appropriate experimental models of the human disease are indispensable to the understanding of successful treatment modalities for osteonecrosis. In the present experiment we devised a novel rabbit model of steroid-induced osteonecrosis by use of two low-dose LPS and three high-dose MPS to investigate the development of osteonecrosis. Thirty eight rabbits were used and tissue assessments were performed on proximal third and distal condyles of femora and humeri obtained 6 weeks after the administration of LPS and MPS. MRI of these regions and intraosseous pressure of proximal femur were obtained at 0 and 6 weeks. Other assessments included serum plasminogen activator/inhibitor ratio, cholesterol level, LDL/HDL ratio, and triglyceride levels at various time points. The study showed that with this osteonecrosis induction protocol there was low animal mortality (6.2%), high rate of osteonecrosis (90%), induction of thrombotic state, and hypercholesterol/lipidemia. On the whole, this is a novel modified animal model of steroid associated osteonecrosis and it would be useful for elucidating the pathogenesis of steroid associated osteonecrosis and developing preventive and therapeutic strategies.