剪切应力对椎体终板的影响

Effects of shear force on vertebral endplate

中文关键词:  椎间盘退变  动物模型  剪切应力  椎体终板

英文关键词:Disc degeneration  Animal model  Shear force  Vertebral endplate

中文摘要:

  【摘要】 目的：通过建立剪切应力加载椎间盘的在体动物模型，探索剪切应力与椎体终板退变间的关系。方法：设计剪切应力加载装置（夹持于L4、L5椎体），用于研究剪切应力加载下L4/5椎体终板的变化。选用38只成年雌性日本大耳白兔，随机分成4组。A组（n=10）加载50N的剪切力4周；B组（n=10）加载50N的剪切力8周；C组（n=10）为对照组，只置入加载装置但不加载剪切力，置入加载装置时间为8周；D组（n=8）为非手术空白组。在4周或8周时将各组兔子全麻后进行X线及MRI检查，对透视下椎体终板变化和MRI T2加权像上椎间盘信号强度的改变情况进行观察分析。检查完毕后处死动物取材（兔L4/5椎间盘及椎体终板），固定后HE染色观察椎体终板组织学变化情况，分析剪切应力对椎体终板和椎间盘退变的影响，并行micro-CT检测，通过计算孔隙率（1-相对骨体积）分析剪切应力对椎间盘渗透率的影响。结果：X线观察发现造模后4周（A组）椎间隙开始出现狭窄，椎体终板尚平整，钙化不明显。第8周时（B组）椎间隙狭窄明显，椎体终板出现不同程度钙化，表面不平且发生轻微移位；相对于对照组（C、D组），A、B组椎间隙明显狭窄，两组MRI（T2加权像）椎间盘信号明显降低。HE染色检查发现A、B组椎体终板组织排列紊乱，病理性增生。micro-CT检测计算孔隙率发现A组实验节段范围为28.4%～37.0%，较B组（范围为26.2%～40.0%）无明显统计学差异，但与C、D两组比较可见统计学差异。结论：一定的剪切应力可导致动物椎体终板退变及孔隙率下降，这可能与椎间盘退变有密切的关系。

英文摘要:

  【Abstract】 Objectives: To investigate the effect of shear force on the endplate of rabbit lumbar vertebra and the relationship between shear force and degeneration of the IVD. Methods: A stainless external shear loading attaching to L4 and L5 vertebral bones of the rabbit in a dorsoventral direction device was made to apply a constant shear. 38 skeletally mature female Japanese white rabbits(aging 5-6 months) weighing an average of 3kg were used. The rabbits were randomly assigned into non-operated group(n=8), non-loaded group(n=10) and two experimental groups of shear loading for 1 and 2 months(n=10 for each group) respectively. In the experimental groups, the discs were subjected to shear force by using an external loading device. In non-loaded group, the external loading device was situated, but the discs remained unloaded. After loading, the loading devices were removed at 4 and 8 weeks and the animals were given X-ray and MRI examination, then radiological hallmarks and the signal intenity on T2-weighted MRI were analyzed. After X-ray and MRI examination, the rabbits were killed and lumbar vertebra samples were harvested for micro-CT and histologic studies to demonstrate the influences of shear force on the endplate and disc degeneration in animal model. Then, the porosity was calculated as the average of 1-BV/TV for analyzing the influences of shear force on endplate mobility. Results: All the animals tolerated the application of the external loading device. After 1 month of loading, radiographic findings showed narrowing of L4/5 discs, and the surfaces of endplates were flat. The narrowing of intervertebral space at 2 months was significant less and rough surface or slight lumbar spondylolisthesis was observed. MRI showed a significant decrease in nucleus pulposus area and signal intensity in T2-weighted images. Histologically, disorganization and hyperplasia of the chondrocyte occurred. The porosity of the endplate in group A ranged from 28.4% to 37.0%, which showed no significant differences with group B(ranging 26.2% to 40.0%). However, significant differences were found between the experimental and control groups. Conclusions: Shear force can relieve the injury to the vertebral body. Cartilage degeneration and the reduction of endplate mobility can be induced by long term shear force loading, which may result in disc degeneration.