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

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.

Download Full-text

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

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206189 ◽

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.

Download Full-text

Direct Osmotic Pressure Measurements in Articular Cartilage Demonstrate Nonideal and Concentration-Dependent Phenomena

Journal of Biomechanical Engineering ◽

10.1115/1.4049158 ◽

2020 ◽

Vol 143 (4) ◽

Author(s):

Brandon K. Zimmerman ◽

Robert J. Nims ◽

Alex Chen ◽

Clark T. Hung ◽

Gerard A. Ateshian

Keyword(s):

Articular Cartilage ◽

Stress Relaxation ◽

Osmotic Pressure ◽

Electrostatic Interactions ◽

Swelling Pressure ◽

Confined Compression ◽

Human Cartilage ◽

Poisson Boltzmann ◽

Triphasic Theory

Abstract The osmotic pressure in articular cartilage serves an important mechanical function in healthy tissue. Its magnitude is thought to play a role in advancing osteoarthritis. The aims of this study were to: (1) isolate and quantify the magnitude of cartilage swelling pressure in situ; and (2) identify the effect of salt concentration on material parameters. Confined compression stress-relaxation testing was performed on 18 immature bovine and six mature human cartilage samples in solutions of varying osmolarities. Direct measurements of osmotic pressure revealed nonideal and concentration-dependent osmotic behavior, with magnitudes approximately 1/3 those predicted by ideal Donnan law. A modified Donnan constitutive behavior was able to capture the aggregate behavior of all samples with a single adjustable parameter. Results of curve-fitting transient stress-relaxation data with triphasic theory in febio demonstrated concentration-dependent material properties. The aggregate modulus HA increased threefold as the external concentration decreased from hypertonic 2 M to hypotonic 0.001 M NaCl (bovine: HA=0.420±0.109 MPa to 1.266±0.438 MPa; human: HA=0.499±0.208 MPa to 1.597±0.455 MPa), within a triphasic theory inclusive of osmotic effects. This study provides a novel and simple analytical model for cartilage osmotic pressure which may be used in computational simulations, validated with direct in situ measurements. A key finding is the simultaneous existence of Donnan osmotic and Poisson–Boltzmann electrostatic interactions within cartilage.

Download Full-text

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

Journal of Biomechanical Engineering ◽

10.1115/1.3138473 ◽

1984 ◽

Vol 106 (2) ◽

pp. 151-158 ◽

Cited By ~ 88

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.

Download Full-text

Tensile mechanical properties of bovine articular cartilage: Variations with growth and relationships to collagen network components

Journal of Orthopaedic Research® ◽

10.1016/s0736-0266(03)00030-5 ◽

2003 ◽

Vol 21 (5) ◽

pp. 872-880 ◽

Cited By ~ 176

Author(s):

Amanda K. Williamson ◽

Albert C. Chen ◽

Koichi Masuda ◽

Eugene J.- M. A. Thonar ◽

Robert L. Sah

Keyword(s):

Mechanical Properties ◽

Articular Cartilage ◽

Collagen Network ◽

Bovine Articular Cartilage

Download Full-text

Comparison Between the Hyperelastic Behavior of Fresh and Frozen Equine Articular Cartilage in Various Joints

Journal of Biomechanical Engineering ◽

10.1115/1.4044031 ◽

2019 ◽

Vol 142 (2) ◽

Author(s):

Hyeon Lee ◽

William D. Campbell ◽

Kelcie M. Theis ◽

Margaret E. Canning ◽

Hannah Y. Ennis ◽

...

Keyword(s):

Articular Cartilage ◽

Material Properties ◽

Statistical Models ◽

Solid Phase ◽

Material Constant ◽

Hyperelastic Material ◽

Aggregate Modulus ◽

Significant Difference ◽

Fluid Load ◽

Hyperelastic Model

Abstract Fresh and frozen cartilage samples of the fetlock, carpus, and stifle were collected from 12 deceased horses. Half were measured immediately following extraction, and half were frozen for seven days and then measured. Seven indentations (various normalized displacements) were implemented with an indention rate of 0.1 mm/s. Solid phase aggregate modulus (Es), hyperelastic material constant (α), and fluid load fraction (F′) of equine articular cartilage were assessed using the Ogden hyperelastic model. The properties were statistically compared in various joints (fetlock, carpus, and stifle), and between fresh and frozen samples using various statistical models. There was no statistical difference between the fetlock and carpus in the aggregate modulus (p = 0.5084), while both were significantly different from the stifle (fetlock: p = 0.0017 and carpus: p = 0.0406). For the hyperelastic material constant, no statistical differences between joints were observed (p = 0.3310). For the fluid load fraction, the fetlock and stifle comparison showed a difference (p = 0.0333), while the carpus was not different from the fetlock (p = 0.1563) or stifle (p = 0.3862). Comparison between the fresh and frozen articular cartilage demonstrated no significant difference among the joints in the three material properties: p = 0.9418, p = 0.7031, and p = 0.9313 for the aggregate modulus, the hyperelastic material constant, and the fluid load fraction, respectively.

Download Full-text

An in Situ Dual Indentation and Optimization Method to Determine Mechanical Properties of Articular Cartilage

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176601 ◽

2007 ◽

Author(s):

Jonathan E. Pottle ◽

J.-K. Francis Suh

Keyword(s):

Articular Cartilage ◽

Stress Relaxation ◽

Structural Integrity ◽

Reaction Force ◽

Model Parameters ◽

Unconfined Compression ◽

Confined Compression ◽

Practical Applications

The efficacy of the biphasic poroviscoelastic (BPVE) theory [1] in constitutive modeling of articular cartilage biomechanics is well-established [2–4]. Indeed, this model has been used to simultaneously predict stress relaxation force across confined compression, unconfined compression, and indentation protocols [2,3]. Previous works have also demonstrated success in simultaneously curve-fitting the BPVE model to reaction force and lateral deformation data gathered from stress relaxation tests of articular cartilage in unconfined compression [4]. However, a potential limitation of practical applications of such a successful model is seen in some commonly-employed mechanical testing methods for articular cartilage, such as confined compression and unconfined compression. These methods require the excision of a disk of cartilage from its underlying subchondral base, which likely would compromise the structural integrity of the tissue, causing swelling and curling artifacts of the sample [5]. Indentation represents a testing protocol that can be used with an intact cartilage layer. This results in a specimen more closely resembling cartilage in vivo. Using an agarose gel construct, our previous study [6] has demonstrated that a unique set of the six BPVE model parameters of a soft tissue can be determined readily from in situ dual indentation method using stress relaxation and creep viscoelastic protocols. The objective of the current study is to validate the efficacy of this technique as a means to determine the BPVE material parameters of articular cartilage.

Download Full-text

Effects of radiopharmaceuticals on articular cartilage’s mechanical properties

Nukleonika ◽

10.2478/nuka-2019-0009 ◽

2019 ◽

Vol 64 (2) ◽

pp. 71-74

Author(s):

Nihal Kuzu ◽

Ekrem Cicek

Keyword(s):

Mechanical Properties ◽

Articular Cartilage ◽

Ionizing Radiation ◽

Mechanical Tests ◽

Cartilage Tissue ◽

Proteoglycan Synthesis ◽

Bovine Articular Cartilage ◽

Technetium 99M ◽

Static Mechanical ◽

Radiation Science

Abstract As radiation science and technology advances, nuclear medicine applications are increasing worldwide which necessitate the understanding of biological implications of such practices. Ionizing radiation has been shown to cause degraded matrix and reduced proteoglycan synthesis in cartilage, and the late consequences of which may include degenerative arthritis or arthropathy. Although degenerative effects of the ionizing radiation on cartilage tissue have been demonstrated, the effects on the mechanical properties of articular cartilage are largely unknown. The radiopharmaceuticals, technetium-99m and technetium-99m sestamibi, were utilized on bovine articular cartilage to investigate these effects. We used two different mechanical tests to determine the mechanical properties of articular cartilage. Dynamic and static mechanical tests were applied to calculate compressive modulus for articular cartilage. We observed clearly higher control modulus values than that of experimental groups which account for lesser stiffness in the exposed cartilage. In conclusion, compressive moduli of bovine articular cartilage were found to decrease after radiopharmaceutical exposure, after both instantaneous and equilibrium mechanical experiments.

Download Full-text

Experimental Determination of Dynamic Mechanical Properties of Normal and Decollagenized Bovine Articular Cartilage Using the Split-Hopkinson Pressure Bar Method

The Abstracts of ATEM International Conference on Advanced Technology in Experimental Mechanics Asian Conference on Experimental Mechanics ◽

10.1299/jsmeatem.2019.1008d1415 ◽

2019 ◽

Vol 2019 (0) ◽

pp. 1008D1415

Author(s):

Takahiro Mori ◽

Hiroto Sakurai ◽

Koichi Kobayshi ◽

Makoto Sakamoto ◽

Yuji Tanabe

Keyword(s):

Mechanical Properties ◽

Articular Cartilage ◽

Experimental Determination ◽

Split Hopkinson Pressure Bar ◽

Dynamic Mechanical Properties ◽

Hopkinson Pressure Bar ◽

Bovine Articular Cartilage ◽

Split Hopkinson ◽

Pressure Bar

Download Full-text

In vitro Articular Cartilage Growth with Sequential Application of IGF-1 and TGF-β1 Enhances Volumetric Growth and Maintains Compressive Properties

Journal of Biomechanical Engineering ◽

10.1115/1.4005851 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 7

Author(s):

Nathan T. Balcom ◽

Britta Berg-Johansen ◽

Kristin J. Dills ◽

Jennifer R. Van Donk ◽

Gregory M. Williams ◽

...

Keyword(s):

Mechanical Properties ◽

Articular Cartilage ◽

Growth Factor ◽

Extreme Values ◽

Volumetric Growth ◽

Bovine Articular Cartilage ◽

Poisson's Ratios ◽

Poisson’S Ratios ◽

Tgf Β1

In vitro cultures with insulin-like growth factor-1 (IGF-1) and transforming growth factor-β1 (TGF-β1) have previously been shown to differentially modulate the growth of immature bovine articular cartilage. IGF-1 stimulates expansive growth yet decreases compressive moduli and increases compressive Poisson’s ratios, whereas TGF-β1 maintains tissue size, increases compressive moduli, and decreases compressive Poisson’s ratios. The current study’s hypothesis was that sequential application of IGF-1 and TGF-β1 during in vitro culture produces geometric and compressive mechanical properties that lie between extreme values produced when using either growth factor alone. Immature bovine articular cartilage specimens were harvested and either untreated (D0, i.e., day zero) or cultured in vitro for either 6 days with IGF-1 (D6 IGF), 12 days with IGF-1 (D12 IGF), or 6 days with IGF-1 followed by 6 days with TGF-β1 (D12 SEQ, i.e., sequential). Following treatment, all specimens were tested for geometric, biochemical, and compressive mechanical properties. Relative to D0, D12 SEQ treatment enhanced volumetric growth, but to a lower value than that for D12 IGF. Furthermore, D12 SEQ treatment maintained compressive moduli and Poisson’s ratios at values higher and lower, respectively, than those for D12 IGF. Considering the previously described effects of 12 days of treatment with TGF-β1 alone, D12 SEQ induced both growth and mechanical property changes between those produced with either IGF-1 or TGF-β1 alone. The results suggest that it may be possible to vary the durations of select growth factors, including IGF-1 and TGF-β1, to more precisely modulate the geometric, biochemical, and mechanical properties of immature cartilage graft tissue in clinical repair strategies.

Download Full-text