Adouni Malek, Faisal Tanvir R, Dhaher Yasin Y
Northwestern University, Physical Medicine and Rehabilitation Department, 345 East Superior Street, Chicago, IL, 60611, United States; Australian College of Kuwait, Mechanical Engineering Department, East Meshrif, P.O. Box 1411, Kuwait.
Department of Mechanical Engineering, University of Louisiana at Lafayette, LA, 70508, USA.
Comput Biol Med. 2020 Nov;126:104012. doi: 10.1016/j.compbiomed.2020.104012. Epub 2020 Oct 7.
The biomechanical function of connective tissues in a knee joint is to stabilize the kinematics-kinetics of the joint by augmenting its stiffness and limiting excessive coupled motion. The connective tissues are characterized by an in vivo reference configuration (in situ strain) that would significantly contribute to the mechanical response of the knee joint. In this work, a novel iterative method for computing the in situ strain at reference configuration was presented. The framework used an in situ strain gradient approach (deformed reference configuration) and a detailed finite element (FE) model of the knee joint. The effect of the predicted initial configuration on the mechanical response of the joint was then investigated under joint axial compression, passive flexion, and coupled rotations (adduction and internal), and during the stance phase of gait. The inclusion of the reference configuration has a minimal effect on the knee joint mechanics under axial compression, passive flexion, and at two instances (0% and 50%) of the stance phase of gait. However, the presence of the ligaments in situ strains significantly increased the joint stiffness under passive adduction and internal rotations, as well as during the other simulated instances (25%, 75% and 100%) of the stance phase of gait. Also, these parameters substantially altered the local loading state of the ligaments and resulted in better agreement with the literature during joint flexion. Therefore, the proposed computational framework of ligament in situ strain will help to overcome the challenges in considering this crucial biological aspect during knee joint modeling. Besides, the current construct is advantageous for a better understanding of the mechanical behavior of knee ligaments under physiological and pathological states and provide relevant information in the design of reconstructive treatments and artificial grafts.
膝关节中结缔组织的生物力学功能是通过增强其刚度和限制过度的耦合运动来稳定关节的运动学-动力学。结缔组织的特征在于体内参考构型（原位应变），这将对膝关节的力学响应有显著贡献。在这项工作中，提出了一种用于计算参考构型下原位应变的新型迭代方法。该框架使用原位应变梯度方法（变形参考构型）和膝关节的详细有限元（FE）模型。然后在关节轴向压缩、被动屈曲、耦合旋转（内收和内旋）以及步态站立期研究预测的初始构型对关节力学响应的影响。在轴向压缩、被动屈曲以及步态站立期的两个时刻（0%和50%），参考构型的纳入对膝关节力学的影响最小。然而，韧带原位应变的存在显著增加了被动内收和内旋以及步态站立期其他模拟时刻（25%、75%和100%）下的关节刚度。此外，这些参数极大地改变了韧带的局部加载状态，并在关节屈曲时与文献结果达成了更好的一致。因此，所提出的韧带原位应变计算框架将有助于克服膝关节建模过程中考虑这一关键生物学方面时所面临的挑战。此外，当前的构建对于更好地理解膝关节韧带在生理和病理状态下的力学行为具有优势，并在重建治疗和人工移植物设计中提供相关信息。
