Auckland University of Technology, Department of Mechanical Engineering, Auckland, New Zealand.
Department of Anatomy, University of Otago, Dunedin, New Zealand Department of Anatomy, Dunedin, New Zealand.
Biomed Res Int. 2019 Jan 9;2019:3973170. doi: 10.1155/2019/3973170. eCollection 2019.
Computational modeling of the human pelvis using the finite elements (FE) method has become increasingly important to understand the mechanisms of load distribution under both healthy and pathologically altered conditions and to develop and assess novel treatment strategies. The number of accurate and validated FE models is however small, and given models fail resembling the physiologic joint motion in particular of the sacroiliac joint. This study is aimed at using an inverted validation approach, using load deformation data to refine an existing FE model under the same mode of load application and to parametrically assess the influence of altered morphology and mechanical data on the kinematics of the model. An osteoligamentous FE model of the pelvis including the fifth lumbar vertebra was used, with highly accurate representations of ligament orientations. Material properties were altered parametrically for bone, cartilage, and ligaments, followed by changes in bone geometry (solid versus 3 and 2 mm shell) and material models (linear elastic, viscoelastic, and hyperelastic isotropic), and the effects of varying ligament fiber orientations were assessed. Elastic modulus changes were more decisive in both linear elastic and viscoelastic bone, cartilage, and ligaments models, especially if shell geometries were used for the pelvic bones. Viscoelastic material properties gave more realistic results. Surprisingly little change was observed as a consequence of altering SIJ ligament orientations. Validation with experiments using cadavers showed close correlations for movements especially for 3 mm shell viscoelastic model. This study has used an inverted validation approach to refine an existing FE model, to give realistic and accurate load deformation data of the osteoligamentous pelvis and showed which variation in the outcomes of the models are attributed to altered material properties and models. The given approach furthermore shows the value of accurate validation and of using the validation data to fine tune FE models.
使用有限元（FE）方法对人体骨盆进行计算建模对于理解健康和病理改变条件下的负荷分布机制以及开发和评估新的治疗策略变得越来越重要。然而，准确且经过验证的 FE 模型数量很少，并且给定的模型无法准确模拟生理关节运动，特别是骶髂关节的运动。本研究旨在使用反向验证方法，使用负荷-变形数据在相同的加载方式下对现有 FE 模型进行细化，并对改变的形态和力学数据对模型运动学的影响进行参数评估。使用包括第五腰椎在内的骨盆骨-韧带 FE 模型，对韧带方向进行了高度准确的表示。通过参数化改变骨骼、软骨和韧带的材料特性，随后改变骨骼几何形状（实体与 3 毫米和 2 毫米壳）和材料模型（线弹性、粘弹性和各向同性超弹性），评估了改变韧带纤维方向的影响。弹性模量的变化在线弹性和粘弹性骨骼、软骨和韧带模型中更为决定性，特别是如果使用骨盆骨骼的壳几何形状。粘弹性材料特性给出了更现实的结果。出人意料的是，由于改变了骶髂关节韧带的方向，观察到的变化很小。使用尸体进行的验证实验表明，运动的相关性非常高，特别是对于 3 毫米壳粘弹性模型。本研究使用反向验证方法对现有 FE 模型进行了细化，为骨-韧带骨盆提供了真实准确的负荷-变形数据，并显示了模型结果的哪些变化归因于改变的材料特性和模型。所提出的方法进一步展示了准确验证和使用验证数据来微调 FE 模型的价值。
