中文摘要：

目的：运用新的MR技术一动态Gd增强MR成像，观察髋关节极度外展固定仅30min时股骨头骨骺血流灌注的变化：观察在骨骺的供养血管被阻塞时，干骺端血管对骨骺软骨及生长板软骨的血供所起的作用。材料与方法：本项实验包括16例两周龄大小的乳猪。在正常对照组。6例乳猪按自然体位进行双侧髋关节MR扫描，主要扫描序列为Gd增强MR成像，即包括动态Gd增强成像和SE T1WI。在外展固定组，将10例乳猪的双侧髋关节持续外展固定30min，进行相同序列的MR扫描，扫描完毕后允许乳猪自由行走，24h后按双侧髋关节自然体位进行MR重复扫描。将外展固定时股骨头各个不同解剖区域的增强率与自然体位时的增强率进行比较对照，并作相应组织学观察研究。结果：外展固定时股骨头的生长板、干骺端的Spongiosa、股骨头前部及后部增强率明显低于自然体位时各相应部位的增强率（P〈0．05），且强化时间显著减慢（p〈0．05），但在Gd增强SE T1WI却无异常发现。24h后MR成像显示血液的再灌注已恢复，且相应组织学研究显示，未见股骨头的损伤及坏死。同时在缺血组，强化的顺序是从干骺端开始，然后到生长板和骨骺，所有缺血性股骨头的组织学研究显示了生长板内较正常股骨头更多的穿通血管。结论：髋关节极度外展固定仅30min即可引起股骨头骨骺缺血，动态Gd增强MR技术能够检出这种股骨头骨骺的超早期缺血。在骨骺血管阻塞时，干骺端的血管提供骨骺和生长板的血供。

英文摘要：

Objective： To evaluate the change of perfusion in super-early ischemia of growth cartilage of femoral head induced by hyperabduction and its characterization of blood perfusion. Materials and Methods： Thirty-two femoral heads of 16 two-week-old piglets were studied. At the beginning all piglets were placed with hips in neutral position and MR scans were performed. After MR exams, all piglets were placed with bilateral hips in consistent hyperabduction for 30 minutes and the same MR exams were repeated. After that, all piglets were allowed to ambulate. After 24 hours the same MRI was performed again. The main MR sequences included perfusion MR imaging and conventional Gd-enhanced SE T1WI. Enhancement ratios of the various anatomic regions of femoral heads in hips with hyperabduction were compared with those in hips with neutral position. The corresponding histologic findings were evaluated. Results： The enhancement ratios of physes and Spongiosas of femoral heads with hips in hyperabduction were significantly less than those in normal physes and Spongiosas （P〈0.05）. Physes and spengiosas with hyperabduction enhanced significantly slower than those with neutral position （P〈0.05）. The MRI appearances of growth cartilage after ambulation were the same as those before abduction. Histologic findings showed no evidence of osteonecrosis or necrosis of chondrocyte. The transphyseal vessels in these piglets with hyperabduction were confirmed histologically. Conclusions： Perfusion MRI can detect super-early ischemia of growth cartilage of femoral head induced by hips with hyperabduction.