EFFECTS OF PULSE METHYLPREDNISOLONE ON BONE AND MARROW TISSUES - CORTICOSTEROID-INDUCED OSTEONECROSIS IN RABBITS

Objective. To investigate the effects of pulse methylprednisolone acet ate on bone and bone marrow tissues and to clarify the causal factors of corticosteroid-induced osteonecrosis (ON) by using an experimental animal model. Methods. Male adult Japanese white rabbits were injected once with 20 mg/kg of methylprednisolone into the right gluteus mediu s muscle; Seven rabbits were killed at 4 weeks, 4 at 6 weeks, 4 at 8 w eeks, and 6 at 10 weeks. Both histopathologic and hematologic studies were performed every week. Results. By 4 weeks after the steroid injec tion, 43% of the rabbits studied had developed multifocal ON lesions i n the femur and/or humerus. In 1 rabbit, a thrombus was detected in an arteriole adjacent to the necrotic area at 4 weeks, After 6 weeks, th ere was also progressive histologic evidence of revascularization, ,vi th granulation tissue, and osteoblastic repair, with appositional bone formation, Hyperlipemia, fatty liver, and intraosseous fat embolism w ere observed in conjunction with thrombocytopenia and hypofibrinogenem ia. Conclusion. A single injection of high-dose corticosteroids was fo und to be capable of inducing thrombocytopenia, hypofibrinogenemia, an d hyperlipemia with multifocal ON in several bones.