Apparatus for Measuring the Swelling Dependent Electrical Conductivity of Charged Hydrated Soft Tissues

This paper describes a new apparatus and method for measuring swelling dependent electrical conductivity of charged hydrated soft tissues. The apparatus was calibrated using a conductivity standard. Swelling dependent specific conductivity of porcine annulus fibrosis (AF) samples was determined. The conductivity values for porcine AF were similar to those for human and bovine articular cartilage found in the literature. Results revealed a significant linear correlation between specific conductivity and water content for porcine AF tissues tested in phosphate buffered saline (PBS).

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Relaxation and Creep Quasilinear Viscoelastic Models for Normal Articular Cartilage

Journal of Biomechanical Engineering ◽

10.1115/1.3138474 ◽

1984 ◽

Vol 106 (2) ◽

pp. 159-164 ◽

Cited By ~ 45

Author(s):

B. R. Simon ◽

R. S. Coats ◽

S. L.-Y. Woo

Keyword(s):

Articular Cartilage ◽

Soft Tissues ◽

Least Squares Method ◽

Viscoelastic Model ◽

Generalized Least Squares ◽

Constitutive Law ◽

Analytical Models ◽

Creep Data ◽

Bovine Articular Cartilage ◽

Generalized Least Squares Method

A quasilinear viscoelastic model was used to develop relaxation and creep forms for a constitutive law for soft tissues. Combined relaxation and cyclic test data as well as preconditioned and nonpreconditioned creep data were used to demonstrate the approach for normal bovine articular cartilage. Values for mechanical parameters in the analytical models were determined using a generalized least squares method.

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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.

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Tetrapolar Measurement of Electrical Conductivity and Thickness of Articular Cartilage

Journal of Biomechanical Engineering ◽

10.1115/1.1785805 ◽

2004 ◽

Vol 126 (4) ◽

pp. 475-484 ◽

Cited By ~ 12

Author(s):

J. S. Binette ◽

M. Garon ◽

P. Savard ◽

M. D. McKee ◽

M. D. Buschmann

Keyword(s):

Electrical Conductivity ◽

Articular Cartilage ◽

Subchondral Bone ◽

Articular Surface ◽

Cartilage Thickness ◽

Therapeutic Interventions ◽

Bovine Articular Cartilage ◽

Calcified Cartilage ◽

Non Destructive

A tetrapolar method to measure electrical conductivity of cartilage and bone, and to estimate the thickness of articular cartilage attached to bone, was developed. We determined the electrical conductivity of humeral head bovine articular cartilage and subchondral bone from a 1- to 2-year-old steer to be 1.14±0.11S/m(mean±sd,n=11) and 0.306±0.034S/m,(mean±sd,n=3), respectively. For a 4-year-old cow, articular cartilage and subchondral bone electrical conductivity were 0.88±0.08S/m(mean±sd,n=9) and 0.179±0.046S/m(mean±sd,n=3), respectively. Measurements on slices of cartilage taken from different distances from the articular surface of the steer did not reveal significant depth-dependence of electrical conductivity. We were able to estimate the thickness of articular cartilage with reasonable precision (<20% error) by injecting current from multiple electrode pairs with different inter-electrode distances. Requirements for the precision of this method to measure cartilage thickness include the presence of a distinct layer of calcified cartilage or bone with a much lower electrical conductivity than that of uncalcified articular cartilage, and the use of inter-electrode distances of the current injecting electrodes that are on the order of the cartilage thickness. These or similar methods present an attractive approach to the non-destructive determination of cartilage thickness, a parameter that is required in order to estimate functional properties of cartilage attached to bone, and evaluate the need for therapeutic interventions in arthritis.

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