A Continuum Theory and an Experiment for the Ion-Induced Swelling Behavior of Articular Cartilage

1984 ◽  
Vol 106 (2) ◽  
pp. 151-158 ◽  
Author(s):  
E. R. Myers ◽  
W. M. Lai ◽  
V. C. Mow
Keyword(s):  
Articular Cartilage ◽  
Stress Relaxation ◽  
Tensile Force ◽  
Continuum Theory ◽  
Swelling Behavior ◽  
Bovine Articular Cartilage ◽  
Free Swelling ◽  
Transient Force

Swelling of normal bovine articular cartilage equilibrated in NaCl solutions was dimensionally measured in thin strips of tissue. The ion-induced strains show that free swelling of articular cartilage is anisotropic and inhomogeneous. For the molar concentrations used, contraction increased linearly with concentration, defining a “coefficient of chemical contraction” (αc). Isometrically constrained specimens registered a rise in tensile force followed by stress relaxation. An extension of the biphasic theory incorporating this ion-induced strain is proposed. This theory can describe the equilibrium anisotropic swelling behavior of cartilage and explain the transient force history observed in the isometric experiment.

INFLUENCE OF PRE-CONDITIONING LOADS ON BOVINE ARTICULAR CARTILAGE STRESS RELAXATION BEHAVIOR IN CONFINED COMPRESSION

2003 ◽  
Vol 07 (02) ◽  
pp. 145-150
Author(s):  
Diego Correa ◽  
Dennis Cullinane ◽  
Juan Carlos Briceño
Keyword(s):  
Mechanical Properties ◽  
Articular Cartilage ◽  
Stress Relaxation ◽  
Solid Phase ◽  
Test Chamber ◽  
Confined Compression ◽  
Equilibrium Stress ◽  
Bovine Articular Cartilage ◽  
Aggregate Modulus ◽  
Compression Chamber

Articular Cartilage is a load bearing tissue whose microarchitecture, electrochemical composition, and fluid interactions afford it unique mechanical properties. It consists of an extracellular matrix (ECM) interspersed with a sparse population of chondrocytes, varying in density by depth. The structure and mechanical properties of this highly specialized tissue also vary depending on depth from the articular surface; with three specialized zones, each with unique material properties. Typically this tissue is mechanically modeled as a biphasic material, consisting of a solid phase and a fluid phase, which can redistribute itself under loading, altering hydrostatic pressure within the material. Thus, articular cartilage exhibits a time-dependent viscoelastic behavior when subjected to constant loading or deformation, and will reach an equilibrium via stress relaxation and creep behavior. The objective of this study was to test a custom designed confined compression chamber. We characterize the ability of the test chamber to generate curves capable of quantifying the stress relaxation level and equilibrium state in bovine articular cartilage, and to show the preliminary results of a comparison between the equilibrium aggregate modulus (HA) obtained from pre- conditioned and non-conditioned tissues. Using fresh bovine articular cartilage samples, stress relaxation tests were conducted in compression, obtaining equilibrium stress and HA through a linear relation between the initial strain and the equilibrium stress. The test specimens were divided into two groups, one with a pre-conditioning load and the other without. The tests resulted in equilibrium stresses of 0.015 ± 0.0067 MPa for the non-conditioned and 0.067 ± 0.012 MPA for the pre-conditioned, and HA values of 0.205 ± 0.100 MPa for the unconditioned group and 0.878 ± 0.160 MPa in the pre-conditioned group. Our confined compression chamber successfully produced the stress relaxation curve characterizing the mechanical behavior of articular cartilage, defining both the equilibrium stress and HA. Our results suggest that pre-conditioning correlates with a higher equilibrium stress and aggregate modulus based on the fact that pre-loading the specimens reduces the effects of viscoelasticity.

Removal of Sulfated Glycosaminoglycans Has a Differential Effect on Permeability of Bovine Articular Cartilage as Measured by Direct Permeation and Stress Relaxation

2009 ◽  
Author(s):  
Heath B. Henninger ◽  
Clayton J. Underwood ◽  
Gerard A. Ateshian ◽  
Jeffrey A. Weiss
Keyword(s):  
Articular Cartilage ◽  
Stress Relaxation ◽  
Soft Tissues ◽  
Water Movement ◽  
Experimental Treatment ◽  
Test Methods ◽  
Confined Compression ◽  
Interstitial Fluid Flow ◽  
Bovine Articular Cartilage ◽  
The Impact

Permeability is defined as the ability of a fluid to pass through a porous medium. The ease of water movement is a determinant of the interstitial fluid flow-dependent viscoelastic properties of hydrated soft tissues and also modulates transport of solutes. For articular cartilage, permeability has been quantified directly via permeation experiments and indirectly by analyzing the data from stress relaxation testing under confined compression. It is unclear whether these different methods result in consistent measurements. This further complicates quantification of the effect of an experimental treatment on permeability such as the removal of sulfated glycosaminoglycans (GAGs) [1, 2]. The objective of this study was to elucidate the impact of sulfated GAGs on the permeability of articular cartilage using direct permeation versus stress relaxation testing, and to assess any differences in permeability calculated from the two test methods.

Determination of Poisson’s Ratios of Bovine Articular Cartilage in Tension and Compression Using Osmotic and Mechanical Loading

2002 ◽  
Author(s):  
Nadeen O. Chahine ◽  
Christopher C.-B. Wang ◽  
Clark T. Hung ◽  
Gerard A. Ateshian
Keyword(s):  
Articular Cartilage ◽  
Strain Softening ◽  
Articular Surface ◽  
Swelling Pressure ◽  
Solid Matrix ◽  
Concentration Effects ◽  
Bovine Articular Cartilage ◽  
Free Swelling ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

The existence of osmotic pressure inside cartilage gives the tissue a propensity to swell. This swelling pressure is balanced by the tensile stresses generated within the solid matrix at free-swelling [1, 2]. Recent studies have shown that cartilage exhibits significant strain-softening when compressed relative to its free-swelling state [3–5]. Such strain-softening behavior has been physically interpreted within the context of osmotic swelling pressure and tension-compression nonlinearity [4, 9]. This has provided the rationale for extracting both the tensile and compressive Young’s moduli from uniaxial compression tests on the same specimen [4, 5]. The goal of the current study is to optically determine another important elastic property, i.e. the equilibrium Poisson’s ratio of young bovine articular cartilage when uniaxially compressed along its three characteristic directions: parallel and perpendicular to the split-line direction (1- and 2-direction, respectively), and in a direction normal to the articular surface (3-direction). Furthermore, the external bath concentration effects on the Poisson’s ratios will be explored at various strain levels.

Synchronized Heterogeneous Indentation and Stress Relaxation Behavior of Articular Cartilage Upon Macroscopic Compression: A Preliminary Study

2014 ◽  
Author(s):  
Jiayue Shen ◽  
Wenting Gu ◽  
Xavier-lewis Palmer ◽  
Siqi Guo ◽  
Zhili Hao
Keyword(s):  
Articular Cartilage ◽  
Stress Relaxation ◽  
Viscoelastic Behavior ◽  
Relaxation Modulus ◽  
Relaxation Behavior ◽  
Indentation Modulus ◽  
Cartilage Sample ◽  
Stress Relaxation Behavior ◽  
Bovine Articular Cartilage ◽  
Preliminary Study

By using a newly-developed experimental technique that is enabled by a polymer-based microfluidic device for detecting distributed normal loads, a preliminary study is presented on the synchronized heterogeneous indentation and stress relaxation behavior of articular cartilage upon macroscopic compression. In a measurement, a rigid cylinder probe is employed to exert macroscopic indentation or step input to a cartilage sample on the device. Consequently, the synchronized heterogeneous viscoelastic behavior of the sample translates to distributed normal loads acting on the device and is captured by the device. While the macroscopic load acting on a sample is recorded by a load cell, the deflections of a sample along its length are captured by the device. Thus, the measured results essentially are the load-deflection relations of a sample along its length. Full-thickness lapine and bovine articular cartilage samples are prepared and measured. A thorough data analysis is implemented on the recorded data for extracting their instant and relaxed indentation modulus, as well as Young’s relaxation modulus.

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