Distribution of Oxygen, Glucose and Lactate in Degenerated Intervertebral Disc

2009 ◽  
Author(s):  
Chun-Yuh Huang ◽  
Wei Yong Gu
Keyword(s):  
Elastic Modulus ◽  
Intervertebral Disc ◽  
Mechanical Loading ◽  
Material Properties ◽  
Mixture Theory ◽  
Unconfined Compression ◽  
Fixed Charge Density ◽  
Tissue Degeneration ◽  
Solute Diffusivity ◽  
Diffusion And Convection

Poor nutritional supply has been a major concern for the health of intervertebral disc (IVD) since the IVD is the largest avascular tissue in the human body. The transport of vital nutrients to cells relies on diffusion and convection through the extracellular matrix (ECM) in the IVD. Transport and metabolism of nutrients (e.g., oxygen and glucose) within the IVD depend on many factors, including the material properties of ECM (e.g., permeability, elastic modulus, and solute diffusivity), cellular metabolic rates, nutritional supply at the edge of the IVD, and mechanical loading [1–6]. Tissue degeneration alters the material properties of the IVD, such as an increase in elastic modulus and a decrease in water content, fixed charge density, permeability and solute diffusivity [6]. However, the effect of tissue degeneration on transport and metabolism of nutrients in the IVD under mechanical loading has not been elucidated. The objective of this study was to numerically investigate the distribution of glucose, oxygen and lactate in the degenerated IVD under static unconfined compression using the mechano-electrochemical mixture theory [7].

scholarly journals Characterizing the Material Properties of the Kidney and Liver in Unconfined Compression and Probing Protocols with Special Reference to Varying Strain Rate

Biomechanics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 264-280
Author(s):  
Blake Johnson ◽  
Scott Campbell ◽  
Naira Campbell-Kyureghyan
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Material Properties ◽  
Kidney Tissue ◽  
Failure Stress ◽  
Rate Dependency ◽  
Unconfined Compression ◽  
Porcine Tissue ◽  
Liver And Kidney ◽  
Strain Rate Dependency

The liver and kidneys are the most commonly injured organs due to traumatic impact forces applied to the abdomen and pose a challenge to physicians due to a hard-to-diagnose risk of internal bleeding. A better understanding of the mechanism of injury will improve diagnosis, treatment, forensics, and other fields. Finite element modelling is a tool that can aid in this understanding, but accurate material properties are required including the strain rate dependency and the feasibility of using animal tissue properties instead of human. The elastic modulus in a probing protocol and the elastic modulus, failure stress, and failure strain in a compression protocol were found for both liver and kidney tissue from human and porcine specimens at varying strain rates. Increases in the elastic modulus were seen for both the human kidney and liver, but only for the porcine kidney, when comparing the unconfined compression and probing protocols. A strain rate dependency was found for both the liver and kidney properties and was observed to have a larger saturation effect at higher rates for the failure stress than for the elastic modulus. Overall, the material properties of intact liver and kidney were characterized, and the strain rate dependency was numerically modelled. The study findings suggest that some kidney and liver material properties vary from human to porcine tissue. Therefore, it is not always appropriate to use material properties of porcine tissue in computational or physical models of the human liver and kidney.

Effects of Compression on Glucose Consumption in Intervertebral Disc

2008 ◽  
Author(s):  
Chun-Yuh Huang ◽  
Wei Yong Gu
Keyword(s):  
Intervertebral Disc ◽  
Theoretical Study ◽  
Mixture Theory ◽  
Glucose Consumption ◽  
Nutrient Level ◽  
Metabolic Rates ◽  
Unconfined Compression ◽  
Theoretical Formulation ◽  
Tissue Integrity ◽  
Cartilaginous Tissues

Nutrition supply is a concern for the health of avascular cartilaginous tissues such as intervertebral disc (IVD). Maintaining tissue integrity relies on cellular biosynthesis of extracellular matrix, which is an energy demanding process [1]. In the IVD, energy is mainly generated through glycolysis (i.e., glucose consumption). Metabolism of nutrients (e.g., oxygen and glucose) within the IVD depends on local concentrations of nutrients, and coupling effects between nutrient level and metabolic rate [2,3]. Our previous theoretical study had developed a new theoretical formulation by incorporating the metabolic rates of solutes into the mechano-electrochemical mixture theory [4,5]. By using this new theoretical model, the distribution of oxygen and lactate can be predicted within the IVD under static and dynamics compressions [4]. However, the effect of compression on glucose consumption in the IVD has not been studied. The objective of this study was to examine the effects of compression on glucose consumption in the IVD under static and dynamic unconfined compression numerically.

scholarly journals An in silico Framework of Cartilage Degeneration That Integrates Fibril Reorientation and Degradation Along With Altered Hydration and Fixed Charge Density Loss

2021 ◽  
Vol 9 ◽  
Author(s):  
Seyed Ali Elahi ◽  
Petri Tanska ◽  
Rami K. Korhonen ◽  
Rik Lories ◽  
Nele Famaey ◽  
...  
Keyword(s):  
Charge Density ◽  
Water Content ◽  
Mechanical Loading ◽  
Collagen Fibril ◽  
In Silico ◽  
Cartilage Degeneration ◽  
Fe Model ◽  
Unconfined Compression ◽  
Normal Loading ◽  
Fixed Charge Density

Injurious mechanical loading of articular cartilage and associated lesions compromise the mechanical and structural integrity of joints and contribute to the onset and progression of cartilage degeneration leading to osteoarthritis (OA). Despite extensive in vitro and in vivo research, it remains unclear how the changes in cartilage composition and structure that occur during cartilage degeneration after injury, interact. Recently, in silico techniques provide a unique integrated platform to investigate the causal mechanisms by which the local mechanical environment of injured cartilage drives cartilage degeneration. Here, we introduce a novel integrated Cartilage Adaptive REorientation Degeneration (CARED) algorithm to predict the interaction between degenerative variations in main cartilage constituents, namely collagen fibril disorganization and degradation, proteoglycan (PG) loss, and change in water content. The algorithm iteratively interacts with a finite element (FE) model of a cartilage explant, with and without variable depth to full-thickness defects. In these FE models, intact and injured explants were subjected to normal (2 MPa unconfined compression in 0.1 s) and injurious mechanical loading (4 MPa unconfined compression in 0.1 s). Depending on the mechanical response of the FE model, the collagen fibril orientation and density, PG and water content were iteratively updated. In the CARED model, fixed charge density (FCD) loss and increased water content were related to decrease in PG content. Our model predictions were consistent with earlier experimental studies. In the intact explant model, minimal degenerative changes were observed under normal loading, while the injurious loading caused a reorientation of collagen fibrils toward the direction perpendicular to the surface, intense collagen degradation at the surface, and intense PG loss in the superficial and middle zones. In the injured explant models, normal loading induced intense collagen degradation, collagen reorientation, and PG depletion both on the surface and around the lesion. Our results confirm that the cartilage lesion depth is a crucial parameter affecting tissue degeneration, even under physiological loading conditions. The results suggest that potential fibril reorientation might prevent or slow down fibril degradation under conditions in which the tissue mechanical homeostasis is perturbed like the presence of defects or injurious loading.

Analysis and design of thermo-mechanical interfaces

2012 ◽  
Vol 60 (2) ◽  
pp. 205-213
Author(s):  
K. Dems ◽  
Z. Mróz
Keyword(s):  
Optimality Conditions ◽  
Mechanical Loading ◽  
Material Properties ◽  
Structural Response ◽  
External Boundary ◽  
Mechanical Loads ◽  
Internal Interface ◽  
Analysis And Design ◽  
First Order ◽  
Mechanical Nature

Abstract. An elastic structure subjected to thermal and mechanical loading with prescribed external boundary and varying internal interface is considered. The different thermal and mechanical nature of this interface is discussed, since the interface form and its properties affect strongly the structural response. The first-order sensitivities of an arbitrary thermal and mechanical behavioral functional with respect to shape and material properties of the interface are derived using the direct or adjoint approaches. Next the relevant optimality conditions are formulated. Some examples illustrate the applicability of proposed approach to control the structural response due to applied thermal and mechanical loads.

Stress Effects in Drying Polymer Films

1994 ◽  
Vol 356 ◽  
Author(s):  
S. Y. Tam ◽  
L. E. Scriven ◽  
H. K. Stolarski
Keyword(s):  
Thin Films ◽  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Polymer Films ◽  
Material Properties ◽  
Film Surface ◽  
Viscoplastic Material ◽  
Stress Effects ◽  
Diffusion And Convection ◽  
Extra Stress

AbstractA model is developed to predict the magnitude and pattern of stress due to drying of polymer films. This model combines diffusion-and-convection equation with large deformation elasto-viscoplasticity, utilizing concentration dependent elastic and viscoplastic material properties to better represent the behavior of drying thin films.The results show that the highest stress occurs at film surface where the concentration depletion is the highest. The magnitude of this stress is induced by increasing mass transfer across the film surface but reduced by increasing diffusion coefficient. The edge effect is significant but local, limited to about four film thicknesses. Similarly, change in substrate induces extra stress.

scholarly journals Excessive mechanical strain accelerates intervertebral disc degeneration by disrupting intrinsic circadian rhythm

2021 ◽  
Author(s):  
Sheng-Long Ding ◽  
Tai-Wei Zhang ◽  
Qi-Chen Zhang ◽  
Wang Ding ◽  
Ze-Fang Li ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Intervertebral Disc ◽  
Mechanical Loading ◽  
Disc Degeneration ◽  
Intervertebral Disc Degeneration ◽  
Night Shift ◽  
Mechanical Strain ◽  
Inhibitory Effect ◽  
Shift Workers ◽  
Normal Environment

AbstractNight shift workers with disordered rhythmic mechanical loading are more prone to intervertebral disc degeneration (IDD). Our results showed that circadian rhythm (CR) was dampened in degenerated and aged NP cells. Long-term environmental CR disruption promoted IDD in rats. Excessive mechanical strain disrupted the CR and inhibited the expression of core clock proteins. The inhibitory effect of mechanical loading on the expression of extracellular matrix genes could be reversed by BMAL1 overexpression in NP cells. The Rho/ROCK pathway was demonstrated to mediate the effect of mechanical stimulation on CR. Prolonged mechanical loading for 12 months affected intrinsic CR genes and induced IDD in a model of upright posture in a normal environment. Unexpectedly, mechanical loading further accelerated the IDD in an Light-Dark (LD) cycle-disrupted environment. These results indicated that intrinsic CR disruption might be a mechanism involved in overloading-induced IDD and a potential drug target for night shift workers.

Elasto-Plastic Hemispherical Contact Models for Various Mechanical Properties

2005 ◽  
Author(s):  
John J. Quicksall ◽  
Robert L. Jackson ◽  
Itzhak Green
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Material Properties ◽  
Poisson’S Ratio ◽  
Carbon Steels ◽  
Poisson's Ratio ◽  
Aluminum Bronze ◽  
Contact Models ◽  
Element Technique ◽  
Malleable Cast

This work uses the finite element technique to model the elasto-plastic deformation of a hemisphere contacting a rigid flat for various material properties typical of aluminum, bronze, copper, titanium and malleable cast iron. Additionally, this work conducted parametric FEM tests on a generic material in which the elastic modulus and Poisson’s ratio are varied independently while the yield strength is held constant. A larger spectrum of material properties are covered in this work than in most previous works. The results are compared to two previously formulated elasto-plastic models simulating the deformation of a hemisphere in contact with a rigid flat. Both of the previously formulated models use carbon steel mechanical properties to arrive at empirical formulations implied to pertain to various materials. While both models considered several carbon steels with varying yield strengths, they did not test materials with varying Poisson’s ratio or elastic modulus. The previously generated elasto-plastic models give fairly good predictions when compared to the FEM results for various material properties from the current work, except that one model produces more accurate predictions overall, especially at large deformations where other models neglect important trends due to decreases in “hardness” with increasing deformation.

Sign in / Sign up

Export Citation Format

Share Document