An experimental dynamic study on the relationship between histopathological and radiological changes in steroid-induced femoral head osteonecrosis of rabbits

Abstract

Objective To explore the relationship between the histology results and radiographic demonstrations in steroid-induced osteonecrosis of the femoral head in rabbits.Methods Forty-six Japanese white adult rabbits were randomly divided into experimental group and control group.The rabbits were injected intramuscularly with 20 mg/kg of methylprednisolone acetate for 3 days or saline in experimental and control group respectively.The bone dynamic of the femoral head was investigated with histopathologic and radiographic examination including X-ray,CT,MRI and angiography at the time of 2,4,8,12 weeks.Results Histopathological findings revealed that bone marrow cell debris was concentrated;the fat cells of the marrow cavity enlarged,and empty bone lacunae clearly increased at 2 weeks after steroid injection.At the time of 4,8,12 weeks,the necrosis areas became larger and the fat cell proliferated and hypertrophied,and the numbers of bone empty lacunae increased.Radiographic examination demonstrated that plan-film and CT had no significant findings during the period of 2 to 12 weeks.However,MRI showed low spot signal on T_1 weight and high signal on T_2 weisht during 2 to 12 weeks.Angiographic finding demonstrated the diameter of the circumflex femoral arteries decreased.At the time of 4,8,12 weeks,some branch of the circumflex arteries disappeared.Conclusion There is a closed relationship between histopathological findings and the MR demonstrations from 2 to 12 weeks.MRI is a highly sensitive means of diagnosing early experimental osteonecrosis of the femoral head. Key words: Rabbits; Femur head necrosis; Radiography; Diagnosis