骺板损伤的显微CT表现及病理变化研究

A dynamic study on micro computed tomography manifestation and pathological change of epiphyseal plate injury in rat model

目的：探讨实验性骺板损伤修复过程中的显微CT表现及病理变化.方法：取4～5周龄Wistar大鼠50只,选择右侧胫骨制作骺板损伤动物模型,左侧作为对照.分别于造模后1、3、7、11和21 d各选取10只大鼠处死,取双侧胫骨行显微CT扫描,观察损伤骺板的影像特征,并通过组织学切片HE染色,观察骺板内组织细胞的动态改变.结果：①对照侧骺板显微CT及组织形态表现.造模后1d,显微CT图像显示骨骺与干骺端高密度带间波浪形带状低密度区,边缘清晰;造模后7d,骺板轻度变窄;11d后逐渐明显变窄,中间部位较边缘显著;21 d时骺板区密度增高,明显变窄.造模后1d,骺板HE染色切片示骺板4层结构清晰可见,软骨细胞呈柱状规律排列;7 d后幼稚软骨细胞逐渐减少,增殖层细胞柱逐渐稀疏,肥大层宽度减小,细胞膨大、退化,骺板逐渐变窄,其中以造模后21 d表现最明显.②观察侧骺板显微CT及组织形态表现.造模后1d,显微CT可见干骺端骨折;造模后3～7d,骺板宽度先增加,然后趋于正常;11d时骺板宽度减小伴新生骨质形成,干骺端下见迂曲透亮影;21 d时骺板宽度明显变窄,骨桥形成.HE染色显示损伤早期骺板细胞正常结构消失,肥大层结构紊乱,组织出血、水肿;造模后7d时静止层细胞聚集,并大量出现在损伤区,同时软骨细胞增殖活跃;11 d时损伤区出现大量静止层细胞,软骨细胞增殖活跃,成簇的软骨细胞团伸入干骺端;21 d时损伤区见成熟小梁骨横贯干骺端至骨骺.结论：显微CT空间分辨率高,可动态反映骺板损伤的修复过程,是研究实验性小动物骺板损伤理想的影像学检查方法.

Objective：To observe the micro computed tomography （CT）manifestation and pathological change of experimental epiphys- eal plate injury during repairs. Methods： The right tibiaes were fetched out from fifty Wistar rats （ aged 4 - 5 weeks） to build epiphyseal plate injury animal models,while the left tibiaes were treated as controls. At 1,3,7,11 and 21 days after modeling, 10 rats were executed, and their bilateral tibias were fetched out and received micro CT scanning. The imaging features of epiphyseal plate injury were observed. Then the tibias were made into sections and the dynamic changes of cells within epiphyseal plate were observed after HE staining. Results： On the 1 st day after modeling, micro CT images of left tibias showed the low density girdle-shaped area with clear margin between high den- sity areas of osteoepiphysis and metaphysis, and the epiphyseal plate became narrow slightly 7 days after modeling. On the 11 st day after modeling, the epiphyseal plate became narrow obviously, and more obvious changes were found in the centre area compared to the margin ar- ea. The epiphyseal plate became narrow obviously and its density increased at 21 days after modeling. On the 1st day after modeling, HE staining clearly showed 4 layer structure of epiphyseal plate and cartilage cells which lined up in columnar style. Seven days after modeling, the immature cartilage ceils increased gradually, the cell columns in proliferation layer were sparse, the width of hypertrophic layer de- creased ,the cells swelled and degenerated, and the epiphyseal plate became narrow gradually. The most obvious change were found at 21 days after modeling. Metaphysis fractures were found in fight tibias by micro CT scanning at 1 day after modeling. Between 3 and 7 days af- ter modeling, the width of epiphyseal plate increased at first and then tended to be normal. At 11 days after modeling, the width of epiphyseal plate decreased with new bone formation,and the curved lucent shadow were found in the metaphysis. At 21 days after modeling,the width of epiphyseal plate decreased obviously and the bone bridge could be found. The result of HE staining in sections from the right tibias showed that the normal structures of epiphyseal plate cell weT＇e absent and the structures of hypertrophic layer were indiscriminate and the hemorrhage and edema of tissues occured in earlier period after injury. On the 7th day after modeling,the cells gathered in quiescent layer and appeared in the injury zone in large number, at the same time, the cartilage cells proliferated actively. At 11 days after modeling, a large amount of quiescent layer cells appeared in injury zone, and the cartilage cells proliferated actively, and clusters of cartilage cells stretched into metaphysis. At 21 days after modeling, mature trabecular bones traversed metaphysis and osteoepiphysis in the injury zone. Conclusion： With high spatial resolution micro CT can dynamically reflect the reparative process of epiphyseal plate injure, so it is an ideal radiological examination for study of epiphyseal plate injury＇ in small experimental animals.