Computational Biomechanics Lab, Department of Mechanical and Materials Engineering, University of Denver, Denver, CO 80208, USA.
J Biomech. 2009 Oct 16;42(14):2341-8. doi: 10.1016/j.jbiomech.2009.06.028. Epub 2009 Aug 31.
Verified computational models represent an efficient method for studying the relationship between articular geometry, soft-tissue constraint, and patellofemoral (PF) mechanics. The current study was performed to evaluate an explicit finite element (FE) modeling approach for predicting PF kinematics in the natural and implanted knee. Experimental three-dimensional kinematic data were collected on four healthy cadaver specimens in their natural state and after total knee replacement in the Kansas knee simulator during a simulated deep knee bend activity. Specimen-specific FE models were created from medical images and CAD implant geometry, and included soft-tissue structures representing medial-lateral PF ligaments and the quadriceps tendon. Measured quadriceps loads and prescribed tibiofemoral kinematics were used to predict dynamic kinematics of an isolated PF joint between 10 degrees and 110 degrees femoral flexion. Model sensitivity analyses were performed to determine the effect of rigid or deformable patellar representations and perturbed PF ligament mechanical properties (pre-tension and stiffness) on model predictions and computational efficiency. Predicted PF kinematics from the deformable analyses showed average root mean square (RMS) differences for the natural and implanted states of less than 3.1 degrees and 1.7 mm for all rotations and translations. Kinematic predictions with rigid bodies increased average RMS values slightly to 3.7 degrees and 1.9 mm with a five-fold decrease in computational time. Two-fold increases and decreases in PF ligament initial strain and linear stiffness were found to most adversely affect kinematic predictions for flexion, internal-external tilt and inferior-superior translation in both natural and implanted states. The verified models could be used to further investigate the effects of component alignment or soft-tissue variability on natural and implant PF mechanics.
验证后的计算模型代表了一种研究关节几何形状、软组织约束和髌股（PF）力学之间关系的有效方法。本研究旨在评估一种显式有限元（FE）建模方法，以预测自然和植入膝关节中的 PF 运动学。在 Kansas 膝关节模拟器中，对四个健康尸体标本进行了三维运动学测量，标本在其自然状态和全膝关节置换后，在模拟深膝弯曲活动期间进行了实验。基于医学图像和 CAD 植入物几何形状创建了特定于标本的 FE 模型，其中包括代表髌股内侧和外侧韧带以及股四头肌肌腱的软组织结构。测量的股四头肌载荷和规定的胫股关节运动学用于预测在 10 度到 110 度股骨弯曲之间的孤立 PF 关节的动态运动学。进行了模型敏感性分析，以确定刚性或可变形髌骨表示以及受扰的 PF 韧带力学特性（预张力和刚度）对模型预测和计算效率的影响。可变形分析得出的 PF 运动学预测结果显示，在自然和植入状态下，所有旋转和平移的平均均方根（RMS）差异均小于 3.1 度和 1.7 毫米。使用刚体进行运动学预测会使平均 RMS 值略有增加，达到 3.7 度和 1.9 毫米，同时计算时间减少了五倍。PF 韧带初始应变和线性刚度增加或减少两倍，会对自然和植入状态下的弯曲、内外倾斜和上下平移的运动学预测产生最不利的影响。验证后的模型可用于进一步研究组件对准或软组织可变性对自然和植入 PF 力学的影响。
