骨质疏松症患者行经皮椎间孔镜下腰椎间盘切除术后邻近节段椎间盘生物力学变化的三维有限元分析

Three-dimensional finite element analysis of biomechanical changes of adjacent intervertebral discs after PTED in patients with osteoporosis

目的采用有限元分析评估骨质疏松症患者行经皮椎间孔镜下腰椎间盘切除(percutaneous transforaminal endoscopic discectomy,PTED)手术后邻近节段椎间盘生物力学变化特点,以探讨骨质疏松症对其术后邻近节段退变(adjacent segment degeneration,ASD)的影响。方法构建腰骶部三维有限元模型(模型1),并分别重建骨密度正常(模型2)和骨质疏松的L4-5节段PTED手术模型(模型3)。通过施加不同方向(包括屈曲、伸展、左右侧弯和轴向旋转)的载荷,计算3个模型的L5-S1节段在不同体位下的纤维环剪切应力和等效应力、终板上的等效应力,以及腰骶部模型的总变形量。结果与模型1相比,模型2除了纤维环在伸展状态和终板处于左侧弯时之外,其他载荷条件下的生物力学应力均增加了5%以内的幅度;模型3在多数条件下的生物力学特征均较模型1和模型2显著增加,仅屈曲与左侧弯状态下的终板等效应力低于模型2,伸展状态下的纤维环等效应力低于模型1,此外,模型3中的纤维环应力集中现象较模型1和模型2更为明显。结论骨质疏松可导致PTED术后相邻节段椎间盘生物力学特性的恶化,这种变化可能是导致邻近节段ASD发生的原因之一。

Objective Finite element analysis was used to evaluate the biomechanical characteristics of the adjacent segment of the lumbar disc after percutaneous transluminal endoscopic diskectomy( PTED) in the patients with osteoporosis,so as to explore the effect of osteoporosis on the adjacent segment degeneration( ASD). Methods The three-dimensional finite element model( model 1) of lumbosacral region was constructed,and the L4-5 PTED models of normal BMD( model 2) and osteoporosis( model 3) were reconstructed. By applying loads in different directions( including buckling,stretching,left and right lateral bending and axial rotation),the shear and equivalent stresses of the annulus fibers,the equivalent stresses on the endplate,and the total deformation of the lumbosacral model were calculated for the L5-S1 segments of the three models at different body positions. Results Compared with model 1,the biomechanical stress of model 2 increases by less than 5% except that the fiber ring was in the extension state and the end plate was in the left bending state. The biomechanical characteristics of model 3 in most conditions were significantly increased compared with model 1 and model 2,only the equivalent stress of the end plate in the flexion and left bending state was lower than model 2,the equivalent stress of the fiber ring in the extension state was lower than model 1. In addition,the stress concentration in model 3 was more obvious than that in model 1 and model 2. Conclusion Osteoporosis can lead to the deterioration of the biomechanical properties of adjacent segments after PTED,which may be one of the causes of ASD.