轴向负载对特发性脊柱侧弯的影响机制研究

A mechanistic study on the effect of the axial load on the adolescent idiopathic scoliosis

目的 研究脊柱侧弯轴向负载后椎体、椎间盘、关节突关节和终板等结构的力学响应特征,胸段侧弯畸形对腰椎应力分布的影响.方法 采用已经建立的单胸弯特发性脊柱侧弯的三维有限元模型,通过设置边界条件和载荷后,进行轴向负载模拟计算,最后读取并分析脊柱侧弯不同部位和结构的应力分析结果 .结果 特发性脊柱侧弯轴向负载后胸椎畸形部位应力明显高于脊柱其他部位,且应力集中于凹侧.胸椎和腰椎两侧椎间盘、终板和骨质的应力均呈现明显的不平衡,椎间盘应力主要集中于胸段结构性主弯凹侧纤维环的后外侧区域.关节突关节是轴向负载的主要承担者,胸主弯凹侧的L5-S1关节突关节应力最大.结论 单胸弯脊柱侧弯可导致整个脊柱的椎间盘、关节突关节和终板等结构应力不均匀分布,这种力学响应特征和畸形进展密切相关.长期应力的不对称性分布可以改变椎间盘、终板和椎体骨质内的细胞活动,使特发性脊柱患儿容易更早地出现相关性疾病.

Objective To investigate the mechanical response of the vertebral body, disc, zygapophysial joint, endplate of adolescent idiopathic scoliosis under axial load condition. To study the effect of thoracic scoliosis on the stress distribution of lumbar spine. Methods Three dimensional finite element model of adolescent idiopathic scoliosis was built and imported into the ANSYS software for assigning boundary and loading conditions. The axial loading condition was simulated after entering the .solution modular. The stress results of the different parts and structures of the scoliotic spine were collected and analyzed. Results The stress of the scoliotic site located at the thoracic spine was higher than the other site,especially at the concave site. Scoliosis could result the asymmetric distribution of the stress on the disc, endplate, and zygapophysial joint of the thoracic spine and the lumbar spine.High localized stress was detected at the posterolateral portion of the annulus fibrosus on the concave side of the thoracic major curve. The zygapophysial joint was the main bearer under axial loading condition. The maximum stress occurred at the zygapophysial joint of L5-S1 vertebrae on the concave side of the thoracic major curve. Conclusions Scoliosis can lead to the unbalanced stress distribution of the vertebral body, intervertebral disc, endplate and zygapophysial joint, which is related to the progression of the scoliotic spine. Long term asyrmmetric loading condition may affect the cell activity of the disc,endplate and vertebral body. This may result the associated disease occur earlier in such group.