长骨缺血坏死动物模型的影像学研究

目的动态观察新西兰白兔骨干的形态学改变及X线、CT、磁共振成像(MRI)表现,探讨骨缺血坏死早期病变机制,研究MRI早期检测骨缺血坏死的可能性及其表现。方法选用雄性新西兰白兔30只,随机分为A、B两组,A组15只,脂多糖100μg/kg,两次注射,耳缘静脉注射。并且在第2次注射脂多糖后,静脉内注射3.75mg/kg地塞米松,3次注射,间隔24h;B组,15只兔子,静脉注射生理盐水1mL/kg,5次注射,作为正常对照。分别于1周、1个月、2个月,在各组随机选择4只兔进行骨干X线、CT、MRI检查,取股骨、胫骨及肱骨骨干骨皮质及骨髓组织作组织病理学检查。结果造模1周后可见多个部位的缺血改变,骨骺部位明显;1个月后缺血改变明显,范围扩大。2个月后部分骨干骨髓腔内出现纤维化表现。2个月内X线及CT检查均为阴性,1周时MRI上可见有缺血坏死表现,2周更加明显,2个月时可见纤维化表现。结论骨梗死表现随时间改变逐渐明显。微循环障碍可能与骨缺血坏死的发病机制有关。通过MRI检查,有可能发现早期的骨缺血坏死。X线、CT对于早期骨缺血改变的显示价值有待进一步研究证实。

Radiological and histological features of rabbits model of avascular osteonecrosis

Objective To investigate the morphologic and X-ray,CT,and magnetic resonance imaging(MRI)changes of osteonecrosis of rabbits and to study its initial pathogenesis.To study the appearance of MRI in early stages of osteonecrosis and to detect its values.Methods Thirty New Zealand rabbits were divided into Group A and Group B with 15 animals in each group.In Group A,15 rabbits were given 100 μg/kg of lipopolysaccharide and were injected intravenously with 3.75 mg/kg dexamethasone 3 times at intervals of 24 hours after the second injection of lipopolysaccharide.In Group B,15 rabbits were intravenously injected 1 mL/kg of saline 5 times at intervals of 24 hours.At 1 week,1 month and 2 months after the last injection of lipopolysaccharide,dexamethasone or saline,4 rabbits were examined with X-ray,CT,MRI and histopathologic examination.Rabbits were scanned with MRI,using a 0.5 T ASC-NT Gyroscan unit(Philips)magnet with 16 cm coil,performed in the coronal planes.Results Radiological changes were seen in femoral,tibia,humerus bone of Group A,but not Group B.These changes on MRI were positive,but negative on X-ray,and CT.The level of changes increased with times.These changes on MRI were consistent with the changes of histopathologic changes.Conclusion Bacterial endotoxic reaction and dexamethasone can cause osteonecrosis in rabbits by disseminated intravascular coagulation.The model may be useful in clarifying the etiology and early pathogenesis of human osteonecrosis after corticoid therapy.It is possible for MRI to detect the early stages of bone osteonecrosis,but not X-ray and CT examination.