The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Gerard A Ateshian - One of the best experts on this subject based on the ideXlab platform.

  • the role of interstitial Fluid pressurization in articular cartilage lubrication
    Journal of Biomechanics, 2009
    Co-Authors: Gerard A Ateshian
    Abstract:

    Over the last two decades, considerable progress has been reported in the field of cartilage mechanics that impacts our understanding of the role of interstitial Fluid pressurization on cartilage lubrication. Theoretical and experimental studies have demonstrated that the interstitial Fluid of cartilage pressurizes considerably under Loading, potentially supporting most of the applied Load under various transient or steady-state conditions. The fraction of the total Load supported by Fluid pressurization has been called the Fluid Load support. Experimental studies have demonstrated that the friction coefficient of cartilage correlates negatively with this variable, achieving remarkably low values when the Fluid Load support is greatest. A theoretical framework that embodies this relationship has been validated against experiments, predicting and explaining various outcomes, and demonstrating that a low friction coefficient can be maintained for prolonged Loading durations under normal physiological function. This paper reviews salient aspects of this topic, as well as its implications for improving our understanding of boundary lubrication by molecular species in synovial Fluid and the cartilage superficial zone. Effects of cartilage degeneration on its frictional response are also reviewed.

  • cartilage interstitial Fluid Load support in unconfined compression following enzymatic digestion
    Journal of Biomechanical Engineering-transactions of The Asme, 2004
    Co-Authors: Ines M Basalo, Robert L Mauck, Terriann N Kelly, Steven B Nicoll, Faye H Chen, Clark T Hung, Gerard A Ateshian
    Abstract:

    Interstitial Fluid pressurization plays an important role in cartilage biomechanics and is believed to be a primary mechanism of Load support in synovial joints. The objective of this study was to investigate the effects of enzymatic degradation on the interstitial Fluid Load support mechanism of articular cartilage in unconfined compression. Thirty-seven immature bovine cartilage plugs were tested in unconfined compression before and after enzymatic digestion. The peak Fluid Load support decreased significantly (p<0.0001) from 84±10% to 53±19% and from 80±10% to 46±21% after 18-hours digestion with 1.0 u/mg-wet-weight and 0.7 u/mg-wet-weight of collagenase, respectively. Treatment with 0.1 u/ml of chondroitinase ABC for 24 hours also significantly reduced the peak Fluid Load support from 83±12% to 48±16% (p<0.0001). The drop in interstitial Fluid Load support following enzymatic treatment is believed to result from a decrease in the ratio of tensile to compressive moduli of the solid matrix.

  • Cartilage interstitial Fluid Load support in unconfined compression following enzymatic digestion.
    Journal of biomechanical engineering, 2004
    Co-Authors: Ines M Basalo, Robert L Mauck, Terriann N Kelly, Steven B Nicoll, Faye H Chen, Clark T Hung, Gerard A Ateshian
    Abstract:

    Interstitial Fluid pressurization plays an important role in cartilage biomechanics and is believed to be a primary mechanism of Load support in synovial joints. The objective of this study was to investigate the effects of enzymatic degradation on the interstitial Fluid Load support mechanism of articular cartilage in unconfined compression. Thirty-seven immature bovine cartilage plugs were tested in unconfined compression before and after enzymatic digestion. The peak Fluid Load support decreased significantly (p

  • cartilage interstitial Fluid Load support in unconfined compression
    Journal of Biomechanics, 2003
    Co-Authors: Seonghun Park, Steven B Nicoll, Ramaswamy Krishnan, Gerard A Ateshian
    Abstract:

    Abstract Under physiological conditions of Loading, articular cartilage is subjected to both compressive strains, normal to the articular surface, and tensile strains, tangential to the articular surface. Previous studies have shown that articular cartilage exhibits a much higher modulus in tension than in compression, and theoretical analyses have suggested that this tension–compression nonlinearity enhances the magnitude of interstitial Fluid pressurization during Loading in unconfined compression, above a theoretical threshold of 33% of the average applied stress. The first hypothesis of this experimental study is that the peak Fluid Load support in unconfined compression is significantly greater than the 33% theoretical limit predicted for porous permeable tissues modeled with equal moduli in tension and compression. The second hypothesis is that the peak Fluid Load support is higher at the articular surface side of the tissue samples than near the deep zone, because the disparity between the tensile and compressive moduli is greater at the surface zone. Ten human cartilage samples from six patellofemoral joints, and 10 bovine cartilage specimens from three calf patellofemoral joints were tested in unconfined compression. The peak Fluid Load support was measured at 79±11% and 69±15% at the articular surface and deep zone of human cartilage, respectively, and at 94±4% and 71±8% at the articular surface and deep zone of bovine calf cartilage, respectively. Statistical analyses confirmed both hypotheses of this study. These experimental results suggest that the tension–compression nonlinearity of cartilage is an essential functional property of the tissue which makes interstitial Fluid pressurization the dominant mechanism of Load support in articular cartilage.

  • inhomogeneous cartilage properties enhance superficial interstitial Fluid support and frictional properties but do not provide a homogeneous state of stress
    Journal of Biomechanical Engineering-transactions of The Asme, 2003
    Co-Authors: Ramaswamy Krishnan, Seonghun Park, F Eckstein, Gerard A Ateshian
    Abstract:

    : It has been well established that articular cartilage is compositionally and mechanically inhomogenous through its depth. To what extent this structural inhomogeneity is a prerequisite for appropriate cartilage function and integrity is not well understood. The first hypothesis to be tested in this study was that the depth-dependent inhomogeneity of the cartilage acts to maximize the interstitial Fluid Load support at the articular surface, to provide efficient frictional and wear properties. The second hypothesis was that the inhomogeneity produces a more homogeneous state of elastic stress in the matrix than would be achieved with uniform properties. We have, for the first time, simultaneously determined depth-dependent tensile and compressive properties of human patellofemoral cartilage from unconfined compression stress relaxation tests. The results show that the tensile modulus increases significantly from 4.1 +/- 1.9 MPa in the deep zone to 8.3 +/- 3.7 MPa at the superficial zone, while the compressive modulus decreases from 0.73 +/- 0.26 MPa to 0.28 +/- 0.16 MPa. The experimental measurements were then implemented with the finite-element method to compute the response of an inhomogeneous and homogeneous cartilage layer to Loading. The finite-element models demonstrate that structural inhomogeneity acts to increase the interstitial Fluid Load support at the articular surface. However, the state of stress, strain, or strain energy density in the solid matrix remained inhomogeneous through the depth of the articular layer, whether or not inhomogeneous material properties were employed. We suggest that increased Fluid Load support at the articular surface enhances the frictional and wear properties of articular cartilage, but that the tissue is not functionally adapted to produce homogeneous stress, strain, or strain energy density distributions. Interstitial Fluid pressurization, but not a homogeneous elastic stress distribution, appears thus to be a prerequisite for the functional and morphological integrity of the cartilage.

Qing-liang Wang - One of the best experts on this subject based on the ideXlab platform.

  • Biotribology behavior and Fluid Load support of PVA/HA composite hydrogel as artificial cartilage
    Wear, 2017
    Co-Authors: Kai Chen, Linmin Xu, Xuehui Yang, Dekun Zhang, Xin Zhang, Qing-liang Wang
    Abstract:

    Abstract The human body joint motion is very complicated, which mainly includes sliding, swing, rotation. Therefore, cartilage covering the joint surface bears the repeated friction which is caused by the different movements during the whole life. So sliding, swing and torsion friction behavior of hydrogels need to be researched as synthetic articular cartilage. In this paper, PVA/HA composite hydrogel is cross-linked on the UHMWPE surface through chemical grafting and freezing-thawing method. Biotribology behavior and Fluid Load support are researched. The results show that swing and torsion friction coefficients are negligibly small, while sliding friction coefficient is largest. There is a negative linear relationship between Fluid Load support and friction coefficient. Fluid Load supports are relative high under swing and torsion friction, so the swing and torsion friction coefficients are relative low. Hydrogel can be replenished by re-swelling to sustain the Fluid pressurization during friction under lubrication condition. Both Fluid Load support and biphasic lubrication due to its porous structure with large amount of water contribute to the low friction coefficient.

  • biotribology behavior and Fluid Load support of pva ha composite hydrogel as artificial cartilage
    Wear, 2017
    Co-Authors: Kai Chen, Linmin Xu, Xuehui Yang, Dekun Zhang, Xin Zhang, Qing-liang Wang
    Abstract:

    Abstract The human body joint motion is very complicated, which mainly includes sliding, swing, rotation. Therefore, cartilage covering the joint surface bears the repeated friction which is caused by the different movements during the whole life. So sliding, swing and torsion friction behavior of hydrogels need to be researched as synthetic articular cartilage. In this paper, PVA/HA composite hydrogel is cross-linked on the UHMWPE surface through chemical grafting and freezing-thawing method. Biotribology behavior and Fluid Load support are researched. The results show that swing and torsion friction coefficients are negligibly small, while sliding friction coefficient is largest. There is a negative linear relationship between Fluid Load support and friction coefficient. Fluid Load supports are relative high under swing and torsion friction, so the swing and torsion friction coefficients are relative low. Hydrogel can be replenished by re-swelling to sustain the Fluid pressurization during friction under lubrication condition. Both Fluid Load support and biphasic lubrication due to its porous structure with large amount of water contribute to the low friction coefficient.

  • Research on torsional friction behavior and Fluid Load support of PVA/HA composite hydrogel.
    Journal of the mechanical behavior of biomedical materials, 2016
    Co-Authors: Kai Chen, Xuehui Yang, Dekun Zhang, Xin Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Hydrogels have been extensively studied for use as synthetic articular cartilage. This study aimed to investigate (1) the torsional friction contact state and the transformation mechanism of PVA/HA composite hydrogel against CoCrMo femoral head and (2) effects of Load and torsional angle on torsional friction behavior. The finite element method was used to study Fluid Load support of PVA/HA composite hydrogel. Results show Fluid loss increases gradually of PVA/HA composite hydrogel with torsional friction time, leading to Fluid Load support decreases. The contact state changes from full slip state to stick-slip mixed state. As the Load increases, friction coefficient and adhesion zone increase gradually. As the torsional angle increases, friction coefficient and slip trend of the contact interface increase, resulting in the increase of the slip zone and the reduction of the adhesion zone. Fluid loss increases of PVA/HA composite hydrogel as the Load and the torsional angle increase, which causes the decrease of Fluid Load support and the increase of friction coefficient.

  • research on swing friction lubrication mechanisms and the Fluid Load support characteristics of pva ha composite hydrogel
    Tribology International, 2015
    Co-Authors: Kai Chen, Dekun Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Abstract Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate Fluid Load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and Fluid Load support. The friction coefficient increases with contact Load and swing angle. The Fluid flow has an important effect on the Fluid Load support, which decreases with an increase in contact Load and swing angle. The Fluid Load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.

  • Research on swing friction lubrication mechanisms and the Fluid Load support characteristics of PVA–HA composite hydrogel
    Tribology International, 2015
    Co-Authors: Kai Chen, Dekun Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Abstract Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate Fluid Load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and Fluid Load support. The friction coefficient increases with contact Load and swing angle. The Fluid flow has an important effect on the Fluid Load support, which decreases with an increase in contact Load and swing angle. The Fluid Load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.

Kai Chen - One of the best experts on this subject based on the ideXlab platform.

  • Biotribology behavior and Fluid Load support of PVA/HA composite hydrogel as artificial cartilage
    Wear, 2017
    Co-Authors: Kai Chen, Linmin Xu, Xuehui Yang, Dekun Zhang, Xin Zhang, Qing-liang Wang
    Abstract:

    Abstract The human body joint motion is very complicated, which mainly includes sliding, swing, rotation. Therefore, cartilage covering the joint surface bears the repeated friction which is caused by the different movements during the whole life. So sliding, swing and torsion friction behavior of hydrogels need to be researched as synthetic articular cartilage. In this paper, PVA/HA composite hydrogel is cross-linked on the UHMWPE surface through chemical grafting and freezing-thawing method. Biotribology behavior and Fluid Load support are researched. The results show that swing and torsion friction coefficients are negligibly small, while sliding friction coefficient is largest. There is a negative linear relationship between Fluid Load support and friction coefficient. Fluid Load supports are relative high under swing and torsion friction, so the swing and torsion friction coefficients are relative low. Hydrogel can be replenished by re-swelling to sustain the Fluid pressurization during friction under lubrication condition. Both Fluid Load support and biphasic lubrication due to its porous structure with large amount of water contribute to the low friction coefficient.

  • biotribology behavior and Fluid Load support of pva ha composite hydrogel as artificial cartilage
    Wear, 2017
    Co-Authors: Kai Chen, Linmin Xu, Xuehui Yang, Dekun Zhang, Xin Zhang, Qing-liang Wang
    Abstract:

    Abstract The human body joint motion is very complicated, which mainly includes sliding, swing, rotation. Therefore, cartilage covering the joint surface bears the repeated friction which is caused by the different movements during the whole life. So sliding, swing and torsion friction behavior of hydrogels need to be researched as synthetic articular cartilage. In this paper, PVA/HA composite hydrogel is cross-linked on the UHMWPE surface through chemical grafting and freezing-thawing method. Biotribology behavior and Fluid Load support are researched. The results show that swing and torsion friction coefficients are negligibly small, while sliding friction coefficient is largest. There is a negative linear relationship between Fluid Load support and friction coefficient. Fluid Load supports are relative high under swing and torsion friction, so the swing and torsion friction coefficients are relative low. Hydrogel can be replenished by re-swelling to sustain the Fluid pressurization during friction under lubrication condition. Both Fluid Load support and biphasic lubrication due to its porous structure with large amount of water contribute to the low friction coefficient.

  • Research on torsional friction behavior and Fluid Load support of PVA/HA composite hydrogel.
    Journal of the mechanical behavior of biomedical materials, 2016
    Co-Authors: Kai Chen, Xuehui Yang, Dekun Zhang, Xin Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Hydrogels have been extensively studied for use as synthetic articular cartilage. This study aimed to investigate (1) the torsional friction contact state and the transformation mechanism of PVA/HA composite hydrogel against CoCrMo femoral head and (2) effects of Load and torsional angle on torsional friction behavior. The finite element method was used to study Fluid Load support of PVA/HA composite hydrogel. Results show Fluid loss increases gradually of PVA/HA composite hydrogel with torsional friction time, leading to Fluid Load support decreases. The contact state changes from full slip state to stick-slip mixed state. As the Load increases, friction coefficient and adhesion zone increase gradually. As the torsional angle increases, friction coefficient and slip trend of the contact interface increase, resulting in the increase of the slip zone and the reduction of the adhesion zone. Fluid loss increases of PVA/HA composite hydrogel as the Load and the torsional angle increase, which causes the decrease of Fluid Load support and the increase of friction coefficient.

  • research on swing friction lubrication mechanisms and the Fluid Load support characteristics of pva ha composite hydrogel
    Tribology International, 2015
    Co-Authors: Kai Chen, Dekun Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Abstract Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate Fluid Load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and Fluid Load support. The friction coefficient increases with contact Load and swing angle. The Fluid flow has an important effect on the Fluid Load support, which decreases with an increase in contact Load and swing angle. The Fluid Load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.

  • Research on swing friction lubrication mechanisms and the Fluid Load support characteristics of PVA–HA composite hydrogel
    Tribology International, 2015
    Co-Authors: Kai Chen, Dekun Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Abstract Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate Fluid Load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and Fluid Load support. The friction coefficient increases with contact Load and swing angle. The Fluid flow has an important effect on the Fluid Load support, which decreases with an increase in contact Load and swing angle. The Fluid Load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.

Dekun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Biotribology behavior and Fluid Load support of PVA/HA composite hydrogel as artificial cartilage
    Wear, 2017
    Co-Authors: Kai Chen, Linmin Xu, Xuehui Yang, Dekun Zhang, Xin Zhang, Qing-liang Wang
    Abstract:

    Abstract The human body joint motion is very complicated, which mainly includes sliding, swing, rotation. Therefore, cartilage covering the joint surface bears the repeated friction which is caused by the different movements during the whole life. So sliding, swing and torsion friction behavior of hydrogels need to be researched as synthetic articular cartilage. In this paper, PVA/HA composite hydrogel is cross-linked on the UHMWPE surface through chemical grafting and freezing-thawing method. Biotribology behavior and Fluid Load support are researched. The results show that swing and torsion friction coefficients are negligibly small, while sliding friction coefficient is largest. There is a negative linear relationship between Fluid Load support and friction coefficient. Fluid Load supports are relative high under swing and torsion friction, so the swing and torsion friction coefficients are relative low. Hydrogel can be replenished by re-swelling to sustain the Fluid pressurization during friction under lubrication condition. Both Fluid Load support and biphasic lubrication due to its porous structure with large amount of water contribute to the low friction coefficient.

  • biotribology behavior and Fluid Load support of pva ha composite hydrogel as artificial cartilage
    Wear, 2017
    Co-Authors: Kai Chen, Linmin Xu, Xuehui Yang, Dekun Zhang, Xin Zhang, Qing-liang Wang
    Abstract:

    Abstract The human body joint motion is very complicated, which mainly includes sliding, swing, rotation. Therefore, cartilage covering the joint surface bears the repeated friction which is caused by the different movements during the whole life. So sliding, swing and torsion friction behavior of hydrogels need to be researched as synthetic articular cartilage. In this paper, PVA/HA composite hydrogel is cross-linked on the UHMWPE surface through chemical grafting and freezing-thawing method. Biotribology behavior and Fluid Load support are researched. The results show that swing and torsion friction coefficients are negligibly small, while sliding friction coefficient is largest. There is a negative linear relationship between Fluid Load support and friction coefficient. Fluid Load supports are relative high under swing and torsion friction, so the swing and torsion friction coefficients are relative low. Hydrogel can be replenished by re-swelling to sustain the Fluid pressurization during friction under lubrication condition. Both Fluid Load support and biphasic lubrication due to its porous structure with large amount of water contribute to the low friction coefficient.

  • Research on torsional friction behavior and Fluid Load support of PVA/HA composite hydrogel.
    Journal of the mechanical behavior of biomedical materials, 2016
    Co-Authors: Kai Chen, Xuehui Yang, Dekun Zhang, Xin Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Hydrogels have been extensively studied for use as synthetic articular cartilage. This study aimed to investigate (1) the torsional friction contact state and the transformation mechanism of PVA/HA composite hydrogel against CoCrMo femoral head and (2) effects of Load and torsional angle on torsional friction behavior. The finite element method was used to study Fluid Load support of PVA/HA composite hydrogel. Results show Fluid loss increases gradually of PVA/HA composite hydrogel with torsional friction time, leading to Fluid Load support decreases. The contact state changes from full slip state to stick-slip mixed state. As the Load increases, friction coefficient and adhesion zone increase gradually. As the torsional angle increases, friction coefficient and slip trend of the contact interface increase, resulting in the increase of the slip zone and the reduction of the adhesion zone. Fluid loss increases of PVA/HA composite hydrogel as the Load and the torsional angle increase, which causes the decrease of Fluid Load support and the increase of friction coefficient.

  • research on swing friction lubrication mechanisms and the Fluid Load support characteristics of pva ha composite hydrogel
    Tribology International, 2015
    Co-Authors: Kai Chen, Dekun Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Abstract Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate Fluid Load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and Fluid Load support. The friction coefficient increases with contact Load and swing angle. The Fluid flow has an important effect on the Fluid Load support, which decreases with an increase in contact Load and swing angle. The Fluid Load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.

  • Research on swing friction lubrication mechanisms and the Fluid Load support characteristics of PVA–HA composite hydrogel
    Tribology International, 2015
    Co-Authors: Kai Chen, Dekun Zhang, Xiaotong Cui, Qing-liang Wang
    Abstract:

    Abstract Hydrogel has been extensively studied for use as articular cartilage. This study aims to investigate Fluid Load support mechanism of polyvinyl alcohol–hydroxyapatite composite hydrogel. Finite element method is used to study swing friction lubrication mechanism and Fluid Load support. The friction coefficient increases with contact Load and swing angle. The Fluid flow has an important effect on the Fluid Load support, which decreases with an increase in contact Load and swing angle. The Fluid Load support is very high (85%), and the hydrogel has low friction coefficient. It exhibits biphasic and self-generating lubrication mechanism.

David L Burris - One of the best experts on this subject based on the ideXlab platform.

  • Effects of mechanical injury on the tribological rehydration and lubrication of articular cartilage
    Journal of The Mechanical Behavior of Biomedical Materials, 2019
    Co-Authors: Margot S. Farnham, Riley E. Larson, David L Burris, Christopher Price
    Abstract:

    Abstract Healthy articular cartilage is crucial to joint function, as it provides the low friction and Load bearing surface necessary for joint articulation. Nonetheless, joint injury places patients at increased risk of experiencing both accelerated cartilage degeneration and wear, and joint dysfunction due to post-traumatic osteoarthritis (PTOA). In this study, we used our ex vivo convergent stationary contact area (cSCA) explant testing configuration to demonstrate that high-speed sliding of healthy tissues against glass could drive consistent and reproducible recovery of compression-induced cartilage deformation, through the mechanism of ‘tribological rehydration’. In contrast, the presence of physical cartilage damage, mimicking those injuries known to precipitate PTOA, could compromise tribological rehydration and the sliding-driven recovery of cartilage function. Full-thickness cartilage injuries (i.e. fissures and chondral defects) markedly suppressed sliding-driven tribological rehydration. In contrast, impaction to cartilage, which caused surface associated damage, had little effect on the immediate tribomechanical response of explants to sliding (deformation/strain, tribological rehydration, and friction/lubricity). By leveraging the unique ability of the cSCA configuration to support tribological rehydration, this study permitted the first direct ex vivo investigation of injury-dependent strain and friction outcomes in cartilage under testing conditions that replicate and maintain physiologically-relevant levels of Fluid Load support and frictional outcomes under high sliding speeds (80 mm/s) and moderate compressive stresses (~0.3 MPa). Understanding how injury alters cartilage tribomechanics during sliding sheds light on mechanisms by which cartilage's long-term resilience and low frictional properties are maintained, and can guide studies investigating the functional consequences of physical injury and joint articulation on cartilage health, disease, and rehabilitation.

  • tribological and material properties for cartilage of and throughout the bovine stifle support for the altered joint kinematics hypothesis of osteoarthritis
    Osteoarthritis and Cartilage, 2015
    Co-Authors: A C Moore, David L Burris
    Abstract:

    Summary Objective Prior studies suggest that ligament and meniscus tears cause osteoarthritis (OA) when changes in joint kinematics bring underused and underprepared regions of cartilage into contact. This study aims to test the hypothesis that material and tribological properties vary throughout the joint according to the local mechanical environment. Method The local tribological and material properties of bovine stifle cartilage ( N  = 10 joints with 20 samples per joint) were characterized under physiologically consistent contact stress and Fluid pressure conditions. Results Overall, cartilage from the bovine stifle had an equilibrium contact modulus of E c0  = 0.62 ± 0.10 MPa, a tensile modulus of E t  = 4.3 ± 0.7 MPa, and a permeability of k  = 2.8 ± 0.9 × 10 −3  mm 4 /Ns. During sliding, the cartilage had an effective friction coefficient of μ eff  = 0.024 ± 0.004, an effective contact modulus of E c  = 3.9 ± 0.7 MPa and a Fluid Load fraction of F ′ = 0.81 ± 0.03. Tibial cartilage exhibited significantly poorer material and tribological properties than femoral cartilage. Statistically significant differences were also detected across the femoral condyle and tibial plateau. The central femoral condyle exhibited the most favorable properties while the uncovered tibial plateau exhibited the least favorable properties. Conclusions Our findings support a previous hypothesis that altered Loading patterns can cause OA by overLoading underprepared regions. They also help explain why damage to the tibial plateau often precedes damage to the mating femoral condyle following joint injury in animal models. Because the variations are driven by fundamental biological processes, we anticipate similar variations in the human knee, which could explain the OA risk associated with ligament and meniscus tears.

  • Fluid Load support during localized indentation of cartilage with a spherical probe
    Journal of Biomechanics, 2012
    Co-Authors: Edward D Bonnevie, Vincent J Baro, Liyun Wang, David L Burris
    Abstract:

    Abstract Interstitial Fluid pressurization, a consequence of a biphasic tissue structure, is essential to the Load bearing and lubrication properties of articular cartilage. Focal tissue degradation may interfere with this protective mechanism, eventually leading to gross degeneration and osteoarthritis. Our long-term goal is to determine whether local contacts can be used as a means to probe local tissue integrity and functionality. In the present work, Hertzian rate-controlled microindentation was used as a model of the more complicated sliding system to directly determine the effects of contact radius and deformation rate on interstitial Load support. During localized contact between a steel spherical probe and bovine articular cartilage, the equilibrium and non-equilibrium responses were well-fit by the Hertz model ( R 2 >0.998) with a mean equilibrium contact modulus of 0.93 MPa. The effective contact modulus and Fluid Load fraction were independent of indentation depth, contact radius, and normal force; both increased monotonically with indentation rate. At 21 μm/s indentation rate, the cartilage was effectively stiffened by 6-fold with the Fluid pressure supporting 85% of the contact force. The results motivated a simple analytical model that directly links the tribomechanical response (including Fluid Load support) and the Peclet number to measurable material properties and controllable experimental variables. This paper demonstrates that tribological contacts can be used to probe local functional properties. Such measurements can add important insights into the roles of focal tissue damage and impaired local functionality in the pathogenesis of osteoarthritis.