激素诱发兔股骨头坏死发生过程中组织学和影像学动态对比研究

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

目的 研究兔激素性股骨头坏死发生、发展过程中组织学改变和影像学表现之间的相关关系。方法健康成年日本大白兔46只，随饥分为实验组30只，肌内注射甲基泼尼松龙（20mg／kg，1次／d，连续3d）；对照组16只，肌内注射相同剂最生理盐水：分别于注射后2、4、8、12周行X线、CT、MRI与股骨头血管动脉造影检查．并于处死动物前股骨头血管墨汁灌注后进行组织学检查，常规HE染色以及微血栓染色。结果组织学：实验组2周时出现骨髓细胞碎片集聚，骨小梁出现空骨陷窝，骨髓造血组织消失，大量脂肪细胞堆积，墨汁灌注，血管数量减少；4～12周时骨髓内脂肪细胞增大，骨小梁开始萎缩、变细，骨细胞核边聚、固缩，空骨陷窝数增多，骨髓造面组织几乎完全消失，被脂肪组织、脂肪细胞替代填充，墨汁灌注血管消失影像学：2～12周X线、CT均末见异常，在应用激素2周双侧股骨头MRT，加权像显示信号强度明显降低，低信号区呈线样，T2和准T2加权像呈不均匀高信号，高信号区呈线样，并延续至12周。动脉介入造影，2周后即出现股骨头血管管腔变细，4、8周时血管数量减少，尚存在的血管变细。各时间点股骨头坏死组织学改变与MRI异常表现密切相关。对照组均未见明显异常。结论糖皮质激素诱发兔股骨头坏死发生、发展过程中，骨坏死组织学变化和股骨头MRI异常表现密切相关；MRI异常表现在一定程度上可以反映股骨头坏死岳的组织学改变；MRI是早期诊断股骨头坏死最具灵敏度、特异性，并能反映骨坏死真实情况的非侵入性检查方法。

Objective To explore the relationship between the histology results and radiographic demonstrations in steroid-induced osteonecrnsis of the femoral head in rabbits. Methods Forty-six Japanese white adult rabbits were randomly divided into experimental gruup 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 histopathologie and radiographic examination including X-ray, CT, MR1 and angiography at the time of 2, 4, 8, 12 weeks. Resuits 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 T1 weight and high signal on T2 weight 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.