Key Laboratory for Biomechanics and Mechanobiology of the Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, China; Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing 102402, China.
Key Laboratory for Biomechanics and Mechanobiology of the Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, China; Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing 102402, China.
Clin Biomech (Bristol). 2020 Mar;73:149-156. doi: 10.1016/j.clinbiomech.2020.01.002. Epub 2020 Jan 24.
To investigate the effects of over-lordotic curvature after lumbar fusion on the stress and deformations of the adjacent intervertebral discs under constant compressive loads.
Two-level ovine specimens-including three vertebral bodies with two discs-were divided into two groups: Group A (to observe external deformation) and Group B (to observe internal stress and deformations of the discs). Each group consisted of three models: a) intact model, b) increased stiffness + unchanged curvature fusion model, and c) increased stiffness + curvature fusion model. Models were tested at a vertebral pressure of 0.4 MPa for 30 min. Creep deformations and stress distributions in the superior adjacent intervertebral discs were analysed using finite element models.
Stiffness angle of the curvature model was increased by 5° and compared with the intact and stiffness models. In Group A, there was no significant deformation in the superior and adjacent intervertebral discs (P > 0.05), whereas creep deformations of the Group B discs increased significantly. Maximum deformations, with increases of approximately 3.7-fold and 2.8-fold in the vertical and horizontal directions, respectively, occurred at the anterior annulus fibrosus. The vertical and sagittal stress concentrations at the anterior annulus fibrosus had maximum differences of 1.0 MPa and 1.2 MPa, respectively.
Under a continuous compressive load, over-lordotic fusion significantly increases the stress and deformation gradient of the nucleus polposus and annulus fibrosus in the superior, adjacent intervertebral disc, increasing the risk of damage and secondary degeneration of these discs when subjected to daily static loads.
研究腰椎融合术后过度前凸曲率对恒定压缩载荷下相邻椎间盘的应力和变形的影响。
将包括三个椎体和两个椎间盘的两水平羊标本分为两组：A 组（观察外部变形）和 B 组（观察椎间盘的内部应力和变形）。每组由三个模型组成：a）完整模型，b）增加刚度+不变曲率融合模型，和 c）增加刚度+曲率融合模型。在椎体压力为 0.4 MPa 的条件下，对模型进行 30 分钟测试。使用有限元模型分析上相邻椎间盘的蠕变变形和应力分布。
曲率模型的刚度角度增加了 5°，并与完整模型和刚度模型进行了比较。在 A 组中，上相邻椎间盘没有明显的变形（P>0.05），而 B 组的椎间盘蠕变变形显著增加。在前纤维环处，垂直和水平方向的最大变形分别增加了约 3.7 倍和 2.8 倍。前纤维环处的垂直和矢状向的应力集中有最大 1.0 MPa 和 1.2 MPa 的差异。
在持续的压缩载荷下，过度前凸融合显著增加了上相邻椎间盘核纤维环的应力和变形梯度，增加了这些椎间盘在日常静态负荷下受损和继发退化的风险。
