Naserkhaki S, Arjmand N, Shirazi-Adl A, Farahmand F, El-Rich M
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran.
Division of Applied Mechanics, Department of Mechanical Engineering, École Polytechnique, Montréal, Canada.
J Biomech. 2018 Mar 21;70:33-42. doi: 10.1016/j.jbiomech.2017.05.003. Epub 2017 May 16.
Ligaments assist trunk muscles in balancing external moments and providing spinal stability. In absence of the personalized material properties for ligaments, finite element (FE) models use dispersed data from the literature. This study aims to investigate the relative effects of eight different ligament property datasets on FE model responses. Eight L4-L5 models distinct only in ligament properties were constructed and loaded under moment (15Nm) alone or combined with a compressive follower load (FL). Range of motions (RoM) of the disc-alone model matched well in vitro data. Ligament properties significantly affected only sagittal RoMs (∼3.0-7.1° in flexion and ∼3.8-5.8° in extension at 10Nm). Sequential removal of ligaments shifted sagittal RoMs in and out of the corresponding in vitro ranges. When moment was combined with FL, center of rotation matched in vivo data for all models (3.8±0.9mm and 4.3±1.8mm posterior to the disc center in flexion and extension, respectively). Under 15Nm sagittal moments, ligament strains were often smaller or within the in vitro range in flexion whereas some posterior ligament forces approached their failure forces in some models. Ligament forces varied substantially within the models and affected the moment-sharing and internal forces on the disc and facet joints. Intradiscal pressure (IDP) had the greatest variation between models in extension. None of the datasets yielded results in agreement with all reported measurements. Results emphasized the important role of ligaments especially under larger moments and the need for their accurate representation in search for valid spinal models.
韧带协助躯干肌肉平衡外部力矩并提供脊柱稳定性。由于缺乏韧带的个性化材料特性，有限元（FE）模型使用来自文献的分散数据。本研究旨在调查八个不同韧带特性数据集对有限元模型响应的相对影响。构建了八个仅在韧带特性上不同的L4-L5模型，并单独在力矩（15牛米）或与压缩跟随载荷（FL）联合作用下加载。仅椎间盘模型的运动范围（RoM）与体外数据匹配良好。韧带特性仅显著影响矢状面RoM（在10牛米时，屈曲约3.0-7.1°，伸展约3.8-5.8°）。依次去除韧带会使矢状面RoM移出或移入相应的体外范围。当力矩与FL联合时，所有模型的旋转中心与体内数据匹配（屈曲和伸展时分别位于椎间盘中心后方3.8±0.9毫米和4.3±1.8毫米处）。在15牛米的矢状面力矩作用下，韧带应变在屈曲时通常较小或在体外范围内，而在一些模型中，一些后韧带力接近其破坏力。韧带力在模型内变化很大，并影响椎间盘和小关节上的力矩分担和内力。椎间盘内压力（IDP）在伸展时模型间变化最大。没有一个数据集产生的结果与所有报告的测量结果一致。结果强调了韧带的重要作用，尤其是在较大力矩作用下，以及在寻找有效的脊柱模型时准确表示韧带的必要性。
