Bhat Subraya Krishna, Yamada Hiroshi, Kumar Nitesh, Adhikari Raviraja, Bhat N Shyamasunder
Department of Mechanical and Industrial Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Udupi, 576104, Karnataka, India.
Department of Biological Functions Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu, 808-0196, Japan.
J Orthop. 2025 Jan 21;67:148-164. doi: 10.1016/j.jor.2025.01.026. eCollection 2025 Sep.
Low back pain is a critical health issue related to the formation and growth of tears (or lesions), along with degenerative changes, which is commonly observed in the posterior regions of intervertebral discs (IVD) in the lower spine segments. Early and accurate prediction of growth of these tears is a challenging task with immense clinical significance. Finite element method is a promising technique in this direction, however, the combined effects of tears and degeneration in the posterior region of annulus has not been studied. The present work focuses on a numerical evaluation of the contribution of annulus material degeneration, the position of tear and regular physiological movements (extension, flexion, left and right lateral bending) on the growth of the posterior circumferential tear in the annulus of the L5-S1 spinal unit. The material models developed previously to describe degeneration effects were adopted for defining the annulus material. The tear is modelled by altering the mesh to determine its effects in the presence of degeneration in the annulus. Degeneration, which is a loss of functional ability due to age-related effects, influenced the stress response significantly across all types of movements. Flexion movement is found to have the most predominant damaging effect on the tears, evident by the higher stresses along the tear boundary. Tears near the outer periphery of the annulus were likely to experience higher magnitudes of stress for an applied load and, hence, were suggested to be more critical. Extension movement seemed to aid in the recovery of the tear, supporting the results of clinical studies. This study highlights the complex interaction between physiological movements and the progression of posterior circumferential tears under different stages of degeneration, which can enable clinicians to develop and implement suitable patient-specific treatment modalities.
下背痛是一个与撕裂（或损伤）的形成和发展以及退行性变化相关的关键健康问题，常见于下脊柱节段的椎间盘（IVD）后部区域。早期准确预测这些撕裂的发展是一项具有重大临床意义的挑战性任务。有限元方法是朝着这个方向发展的一种很有前景的技术，然而，尚未研究椎间盘环后部撕裂与退变的综合影响。本研究聚焦于对L5-S1脊柱单元椎间盘环后圆周撕裂发展过程中，椎间盘环材料退变、撕裂位置以及正常生理运动（伸展、屈曲、左右侧屈）的贡献进行数值评估。采用先前开发的用于描述退变影响的材料模型来定义椎间盘环材料。通过改变网格来模拟撕裂，以确定其在椎间盘环存在退变情况下的影响。退变是由于年龄相关影响导致的功能丧失，在所有类型的运动中对应力响应有显著影响。发现屈曲运动对撕裂具有最主要的破坏作用，沿撕裂边界的应力较高即证明了这一点。对于施加的载荷，靠近椎间盘环外周的撕裂可能承受更高的应力幅度，因此被认为更为关键。伸展运动似乎有助于撕裂的恢复，这与临床研究结果相符。本研究强调了生理运动与不同退变阶段后圆周撕裂进展之间的复杂相互作用，这可以使临床医生制定并实施合适的针对个体患者的治疗方案。
