A study on the role of articular cartilage soft tissue constitutive form in models of whole knee biomechanics

Abstract

The mechanical behaviors of biological soft tissues are challenging to describe abstractly, with each individual tissue potentially characterized by its own unique nonlinear, anisotropic, and viscoelastic properties. These complexities are exacerbated by patient to patient variability, both mechanically and anatomically, and by inherent constitutive heterogeneity. Despite these challenges, computational models of whole knee biomechanics can be instrumental in describing the onset and progression of injury and disease. In this work, a three-dimensional whole knee computational model was developed using patient-specific anatomy, containing tissues with constitutive relationships built from relevant experimental investigations. In an effort to address the common assumption of linear elastic descriptions of articular cartilage in whole knee models, this work investigates the implications, with respect to macroscopic kinematics and local deformation, of incorporating physiologically motivated and mechanically accurate constitutive heterogeneity in articular cartilage, highlighting the sensitivities of each corresponding level of constitutive complexity. We show how the inclusion of representative cartilage material models affects deformation distributions within the joint, as well as relative joint motion. In particular, the assumption of linear elasticity in articular cartilage results in an overprediction of joint motion and significantly affects predicted local cartilage strains, while full-field, mechanically heterogeneous cartilage descriptions have a less drastic effect at both the tissue and joint levels. Nonetheless, joints containing complete descriptions of articular cartilage heterogeneity may be an integral component in building comprehensive computational tools to advance our understanding of injury and disease mechanisms.

Smart pressure distribution estimation in biological joints for mechanical bio-inspired design

“…To understand the functioning of biological joints, either for medical applications or in the context of mechanical bio-inspired design, numerical models are widely used. The finite element (FE) method was first applied to biological joints in the 80's with the study of the human knee [3][4][5]. Nowadays, the standard in medical biomechanics is anatomically based subject-specific 3D model.…”

“…The same is true for articular cartilage which in practice is found to be nonlinear viscoelastic and heterogeneous. Some rare studies that focus on the role of articular cartilage consider part of this complex behaviour [5]. Finally, ligaments were often modelled as 1D nonlinear springs but tend to be represented by transversely isotropic hyper-elastic elements [6].…”

“…Mechanical properties of bone are mostly derived from CT or MRI scans, whereas those of soft tissues are obtained from literature or by fitting the model to experimental data. In medical biomechanics, the main issues with FE models of biological joints are a poor knowledge of in-vivo loading and boundary conditions [4], as well as uncertainty of mechanical properties of biological materials (high variability among specimens and difficulties to obtain significant samples of fresh biological material) [5]. Biological geometry generation and meshing is also a sensitive aspect which requires a certain expertise due to the surfaces complexity, the low thickness of some components (e.g.…”

An eFTD-VP framework for efficiently generating patient-specific anatomically detailed facial soft tissue FE mesh for craniomaxillofacial surgery simulation

“…FEM allows incorporating highly complex and nonlinear biomechanical tissues behavior, and it is based on a volumetric discretization of the tissue structure through the definition of 3D meshes. The success of FEM simulation depends on the geometrical fidelity of the FE mesh that represents the anatomy of interest (Freutel et al 2014; Wu 2014; Luboz et al 2014; Marchi and Arruda 2017), the accuracy of constitutive properties used to characterize the tissue mechanical behavior, and also realistic boundary conditions. In the FE mesh generation, there are two main challenges.…”

Thin deformable tissues modeling for simulation of arthroscopic knee surgery

“…These models include, single-phase viscoelastic models [10], poroelastic and biphasic models [11], fiber-reinforced nonlinear models [12], and triphasic models [13]. Besides, the properties of cartilages in different situations were also studied, such as influence from other tissues [14], electromechanical properties [15,16], patient-specific constitutive form [17], tissues contact in walking [18], the contribution of constitutive components [19], and the properties in knee cartilage loss [20]. [21,22].…”