Ruberté Lissette M, Natarajan Raghu N, Andersson Gunnar Bj
Department of Bioengineering, University of Illinois at Chicago, USA.
J Biomech. 2009 Feb 9;42(3):341-8. doi: 10.1016/j.jbiomech.2008.11.024. Epub 2009 Jan 10.
The current study investigated mechanical predictors for the development of adjacent disc degeneration. A 3-D finite element model of a lumbar spine was modified to simulate two grades of degeneration at the L4-L5 disc. Degeneration was modeled by changes in geometry and material properties. All models were subjected to follower preloads of 800N and moment loads in the three principal directions of motion using a hybrid protocol. Degeneration caused changes in the loading and motion patterns of the segments above and below the degenerated disc. At the level (L3-L4) above the degenerated disc, the motion increased due to moderate degeneration by 21% under lateral bending, 26% under axial rotation and 28% under flexion/extension. At the level (L5-S1) below the degenerated disc, motion increased only during lateral bending by 20% due to moderate degeneration. Both the L3-L4 and L5-S1 segment showed a monotonic increase in both the maximum von Mises stress and shear stress in the annulus as degeneration progressed for all loading directions, expect extension at L3-L4. The most significant increase in stress was observed at the L5-S1 level during axial rotation with nearly a ten-fold increase in the maximum shear stress and 103% increase in the maximum von Mises stress. The L5-S1 segment also showed a progressive increase in facet contact force for all loading directions with degeneration. Nucleus pressure did not increase significantly for any loading direction at either the caudal or cephalic adjacent segment. Results suggest that single-level degeneration can increase the risk for injury at the adjacent levels.
本研究调查了相邻椎间盘退变发展的力学预测因素。对腰椎的三维有限元模型进行修改，以模拟L4-L5椎间盘的两级退变。通过几何形状和材料特性的变化对退变进行建模。所有模型均采用混合加载方案，在三个主要运动方向上承受800N的随动预载和弯矩载荷。退变导致退变椎间盘上方和下方节段的载荷和运动模式发生变化。在退变椎间盘上方的节段（L3-L4），由于中度退变，在侧弯时运动增加21%，在轴向旋转时增加26%，在屈伸时增加28%。在退变椎间盘下方的节段（L5-S1），由于中度退变，仅在侧弯时运动增加20%。随着退变进展，对于所有加载方向，L3-L4和L5-S1节段的纤维环最大von Mises应力和剪应力均呈单调增加，但L3-L4节段在伸展时除外。在轴向旋转过程中，L5-S1节段的应力增加最为显著，最大剪应力几乎增加了10倍，最大von Mises应力增加了103%。随着退变，L5-S1节段在所有加载方向上的小关节接触力也逐渐增加。在尾侧或头侧相邻节段，对于任何加载方向，髓核压力均未显著增加。结果表明，单节段退变会增加相邻节段受伤的风险。
