Computational simulation of the multiphasic degeneration of the bone-cartilage unit during osteoarthritis via indentation and unconfined compression tests

Abstract

It has been experimentally proposed that the discrete regions of articular cartilage, along with different subchondral bone tissues, known as the bone-cartilage unit, are biomechanically altered during osteoarthritis degeneration. However, a computational framework capturing all of the dominant changes in the multiphasic parameters has not yet been developed. This article proposes a new finite element model of the bone-cartilage unit by combining several validated, nonlinear, depth-dependent, fibril-reinforced, and swelling models, which can computationally simulate the variations in the dominant parameters during osteoarthritis degeneration by indentation and unconfined compression tests. The mentioned dominant parameters include the proteoglycan depletion, collagen fibrillar softening, permeability, and fluid fraction increase for approximately non-advanced osteoarthritis. The results depict the importance of subchondral bone tissues in fluid distribution within the bone-cartilage units by decreasing the fluid permeation and pressure (up to a maximum of 100 kPa) during osteoarthritis, supporting the notion that subchondral bones might play a role in the pathogenesis of osteoarthritis. Furthermore, the osteoarthritis composition-based studies shed light on the significant biomechanical role of the calcified cartilage, which experienced a maximum change of 70 kPa in stress, together with relative load contributions of articular cartilage constituents during osteoarthritis, in which the osmotic pressure bore around 70% of the loads after degeneration. To conclude, the new insights provided by the results reveal the significance of the multiphasic osteoarthritis simulation and demonstrate the functionality of the proposed bone-cartilage unit model.

Biomechanical Characteristics of the Knee Joint during Gait in Obese versus Normal Subjects

“…The articular cartilage was modeled using incompressible hyperelastic fibrils reinforced composites behavior described by Sajjadinia et al [ 31 ]. The Cauchy stress ( ) in the model used was decomposed into non-fibrillar ( ) and fibrillar ( ) parts as follows: where F and J are the deformation gradient tensor and the volumetric deformation, respectively.…”

“…The fibrils were oriented perpendicular to the subchondral junction and turned gradually in the middle zone to become parallel to the articular surface. For more details on the formulation of the material, please see prior works [ 31 , 32 ]. A list of the properties of the material is presented in Table 1 .…”

A parametric study on the mechanical role of fibrillar rotations in an articular cartilage finite element model

“…This way, the fibrillar components along with their rotations were taken into account using the constitutive equations implemented by the Fortran UMAT subroutine. Readers are referred to the previous study [21] for a more detailed explanation of the implementation of the AC model.…”

The effect of highly inhomogeneous biphasic properties on mechanical behaviour of articular cartilage

“…Material properties of AC have a marked impact on its biomechanics. The finite element (FE) method has been widely adopted to study the biomechanics of AC, which could help to understand the unique load-bearing and lubrication properties of AC, prevent or treat osteoarthritis as well as optimize the scaffold design in tissue engineering [2][3][4].…”