A biphasic finite element study on the role of the articular cartilage superficial zone in confined compression

Abstract

The aim of this study was to investigate the role of the superficial zone on the mechanical behavior of articular cartilage. Confined compression of articular cartilage was modeled using a biphasic finite element analysis to calculate the one-dimensional deformation of the extracellular matrix (ECM) and movement of the interstitial fluid through the ECM and articular surface. The articular cartilage was modeled as an inhomogeneous, nonlinear hyperelastic biphasic material with depth and strain-dependent material properties. Two loading conditions were simulated, one where the superficial zone was loaded with a porous platen (normal test) and the other where the deep zone was loaded with the porous platen (upside down test). Compressing the intact articular cartilage with 0.2 MPa stress reduced the surface permeability by 88%. Removing the superficial zone increased the rate of change for all mechanical parameters and decreased the fluid support ratio of the tissue, resulting in increased tissue deformation. Apparent permeability linearly increased after superficial removal in the normal test, yet it did not change in the upside down test. Orientation of the specimen affected the time-dependent biomechanical behavior of the articular cartilage, but not equilibrium behavior. The two tests with different specimen orientations resulted in very different apparent permeabilities, suggesting that in an experimental study which quantifies material properties of an inhomogeneous material, the specimen orientation should be stated along with the permeability result. The current study provides new insights into the role of the superficial zone on mechanical behavior of the articular cartilage.

Osteoarthritis year in review 2016: mechanics

“…Indeed, the strain response of chondrocytes within the superficial zone of the articular cartilage was shown to be highly heterogeneous, showing regional patterns of strain in response to different modes of applied stress, i.e., compression and tension 28 . The loss of the superficial zone was examined using FEM and confirmed an increased permeability and strain of the remaining cartilage 26,60 . Therefore, degeneration of the superficial zone of the articular tissues, which is a common feature of the early stage of OA, compromised the tissue and made chondrocytes vulnerable to strain-induced death.…”

Comparison of iatrogenic articular cartilage injury in canine stifle arthroscopy versus medial parapatellar mini‐arthrotomy in a cadaveric model

“…Complete regeneration of articular cartilage in partial thickness cartilage wounds has not been reported. [8][9][10][11] In contrast, lesions which penetrate the subchondral bone are accessible to reparative cells from the marrow, and can fill by ingrowth of fibrous tissue, fibrocartilage, or hyaline cartilage. 10,11 Unfortunately, this ingrowth does not persist, as adherence of the repair tissue to the surrounding cartilage is often incomplete.…”

“…Complete regeneration of articular cartilage in partial thickness cartilage wounds has not been reported . In contrast, lesions which penetrate the subchondral bone are accessible to reparative cells from the marrow, and can fill by ingrowth of fibrous tissue, fibrocartilage, or hyaline cartilage .…”

Development and analytical validation of a finite element model of fluid transport through osteochondral tissue

“…ConvergenceEvaluation of the effective fluid pressure across three vertical mesh sizes (100, 200, 300 layers per z-stack) revealed a <5% increase in effective fluid pressure between 100 and 200 layers, and 200 and 300 layers (Sup.Figure 1B). Whereas, in the radial mesh study(8,12,16 radial slices) we saw increases in effective fluid pressure of 11.1% and 4.7% between 8 and 12, 12 and 16, respectively (Sup.Figure 1A). Given these results, we built our mesh with 8 theta segments, 12 radial slices, and 100-vertical layers.Compressive stress relaxation:Compressive stress relaxation in the z-direction was observed within both cartilage and bone elements.…”