scholarly journals Effects of Tension-Compression Nonlinearity on Solute Transport in Charged Hydrated Fibrous Tissues Under Dynamic Unconfined Compression

2006 ◽  
Vol 129 (3) ◽  
pp. 423-429 ◽  
Author(s):  
Chun-Yuh Huang ◽  
Wei Yong Gu
Keyword(s):  
Solute Transport ◽  
Soft Tissues ◽  
Dynamic Compression ◽  
Fibrous Tissue ◽  
Dynamic Strain ◽  
Unconfined Compression ◽  
Cartilage Sample ◽  
New Model ◽  
Dynamic Loading Conditions ◽  
High Degree

Cartilage is a charged hydrated fibrous tissue exhibiting a high degree of tension-compression nonlinearity (i.e., tissue anisotropy). The effect of tension-compression nonlinearity on solute transport has not been investigated in cartilaginous tissue under dynamic loading conditions. In this study, a new model was developed based on the mechano-electrochemical mixture model [Yao and Gu, 2007, J. Biomech. Model Mechanobiol., 6, pp. 63–72, Lai et al., 1991, J. Biomech. Eng., 113, pp. 245–258], and conewise linear elasticity model [Soltz and Ateshian, 2000, J. Biomech. Eng., 122, pp. 576–586;Curnier et al., 1995, J. Elasticity, 37, pp. 1–38]. The solute desorption in cartilage under unconfined dynamic compression was investigated numerically using this new model. Analyses and results demonstrated that a high degree of tissue tension-compression nonlinearity could enhance the transport of large solutes considerably in the cartilage sample under dynamic unconfined compression, whereas it had little effect on the transport of small solutes (at 5% dynamic strain level). The loading-induced convection is an important mechanism for enhancing the transport of large solutes in the cartilage sample with tension-compression nonlinearity. The dynamic compression also promoted diffusion of large solutes in both tissues with and without tension-compression nonlinearity. These findings provide a new insight into the mechanisms of solute transport in hydrated, fibrous soft tissues.

Analysis of Solute Transport in Cartilaginous Tissue Under Dynamic Unconfined Compression

2003 ◽  
Author(s):  
Hai Yao ◽  
Wei Yong Gu
Keyword(s):  
Dynamic Compression ◽  
Electrical Potential ◽  
Loading Frequency ◽  
Mechanical Forces ◽  
The Finite Element Method ◽  
Unconfined Compression ◽  
Cartilage Sample ◽  
Cartilaginous Tissues ◽  
Transduction Mechanisms ◽  
Theoretical Analyses

Transport of fluid and solutes through the extracellular matrix plays a key role in the nutrition and growth of cartilaginous tissues that lack blood supply. It has been found that the mechanical loading can alter the transport rates of solutes within cartilage [Bonassar, 2000; O’Hara, 1990; Quinn, 2002]. Dynamic compression may enhance the transport of large solutes (e.g., growth factors) within the tissue. Many theoretical analyses have been reported in literature on the transport of fluid and solutes, as well as physical signals (stress, strain, pressure, concentrations, and electrical potential) in cartilage under unconfined compression [Armstrong, 1984; Levenston, 1999; Mow, 2002]. However, little is known as to how the tissue fixed charge density (FCD) affects the transport of fluid and neutral solutes (e.g., glucose and IGF-1) in cartilage sample in dynamic compression. In this study, we numerically analyzed the transport of fluid and solutes, as well as the mechano-electrochemical signals within the cartilage sample in dynamic unconfined compression, using the finite element method (FEM). The objective of this study was to investigate the effects of FCD, loading frequency, and loading platens (permeable vs. impermeable) on the transport of fluid, ions, and neutral solutes within cartilage. This study is essential for the understanding of tissue nutrition and signal transduction mechanisms in cartilage subjected to mechanical forces.

Development and Verification of a Dynamic TKR Model

2002 ◽  
Author(s):  
Jason P. Halloran ◽  
Anthony J. Petrella ◽  
Paul J. Rullkoetter
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Dynamic Loading ◽  
Soft Tissues ◽  
Dynamic Models ◽  
Total Joint Replacement ◽  
Fe Model ◽  
Loading Conditions ◽  
Dynamic Loading Conditions

The success of current total knee replacement (TKR) devices is contingent on the kinematics and contact mechanics during in vivo activity. Indicators of potential clinical performance of total joint replacement devices include contact stress and area due to articulations, and tibio-femoral and patello-femoral kinematics. An effective way of evaluating these parameters during the design phase or before clinical use is via computationally efficient computer models. Previous finite element (FE) knee models have generally been used to determine contact stresses and/or areas during static or quasi-static loading conditions. The majority of knee models intended to predict relative kinematics have not been able to determine contact mechanics simultaneously. Recently, however, explicit dynamic finite element methods have been used to develop dynamic models of TKR able to efficiently determine joint and contact mechanics during dynamic loading conditions [1,2]. The objective of this research was to develop and validate an explicit FE model of a TKR which includes tibio-femoral and patello-femoral articulations and surrounding soft tissues. The six degree-of-freedom kinematics, kinetics and polyethylene contact mechanics during dynamic loading conditions were then predicted during gait simulation.

Gross and Histologic Changes in the Developing Rabbit Subglottis in Response to a Controlled Depth of Injury

2002 ◽  
Vol 127 (5) ◽  
pp. 442-447 ◽  
Author(s):  
Leila A. Mankarious ◽  
Shilpa R. Cherukupally ◽  
Allison B. Adams
Keyword(s):  
Pilot Study ◽  
Soft Tissues ◽  
Cricoid Cartilage ◽  
Fibrous Tissue ◽  
Biochemical Changes ◽  
Morphologic Change ◽  
Age Group ◽  
Prolonged Intubation ◽  
Structural Support ◽  
Histologic Changes

OBJECTIVE: Our goal was to determine the effects of both perichondrial and intracartilaginous injury in the developing rabbit subglottis versus normal development. DESIGN: We conducted a descriptive, pilot study of changes in the shape and histology of the subglottis after a controlled depth of injury in 27 New Zealand White rabbits, ages 4 weeks, 8 weeks, and 1 1/2 years. INTERVENTION: Within each age group, 3 animals underwent no surgery, 3 underwent perichondrial injury, and 3 underwent intracartilaginous injury. RESULTS: Perichondrially injured animals in the 4-week age group developed a marked abnormality in the shape of the cricoid cartilage in the injured region. Cartilage of the perichondriallly injured animals in the 8-week and 1 1/2-year groups became histologically consistent with fibrous tissue. The cartilage of all animals that underwent intracartilaginous injury was replaced with fibrous tissue. CONCLUSION: In this observational study, we identified 3 relevant findings. First, the responses of the cartilage to a perichondrial injury suggest that the luminal soft tissues may exert some morphologic control in developmentally young animals. Second, only the 4-week-old group's cartilage was tolerant of a perichondrial injury with continued growth of the ring. Third, no animal's cartilage could withstand an intracartilaginous injury regardless of age. Acquired or congenital cricoid cartilage abnormalities are a frequent source of airway distress in both pediatric and adult populations. Narrowing of the cricoid cartilage, as seen in subglottic stenosis (SGS), creates a significant increase in morbidity and mortality rates 1 with an array of surgical interventions described extensively in the otolaryngology literature. The acquired form of SGS usually is iatrogenic, resulting from prolonged intubation or surgical intervention. Few published reports exist describing the histologic changes associated with SGS. Of the published studies, the source of SGS appears to be both cartilage ring abnormalities and concomitant mucosal fibrosis. 2–5 Histologic examination of injured cricoid samples suggests that the abnormal cricoid growth and development may be due to a combination of (1) inflammation within the cartilage leading to loss of chondrocytes, (2) replacement of the cartilage with fibrosis leading to decreased cartilage extracellular matrix and loss of structural support, and/or (3) alterations in the shape of the ring. It is generally accepted that intubation is better tolerated in younger patients than in older patients. Premature infants can be intubated for up to 4 to 5 months, but adults can be intubated for a maximum of 2 to 3 weeks before an alternate airway is sought. However, no exact guidelines exist for the duration of intubation as a function of age. Even physicians who care for intubated patients disagree about when to consider tracheotomy. We began our series of experiments attempting to understand the biochemical changes that would explain the difference in tolerance to intubation and the mechanisms behind loss of the structural support of the cricoid ring. In preparing the experimental substrate for these studies, we identified an interesting age-dependent and depth of injury-dependent morphologic change in the rabbit subglottis that was not expected. Biochemical changes in the rabbit subglottis will follow in future reports; however, herein we report on the observed morphologic changes. Due to the limited number of animals in this study, the data presented represent a pilot study.

A Novel Non-Destructive Method for Measuring Elastic Moduli of Cultivated Cartilage Tissues

2007 ◽  
Vol 342-343 ◽  
pp. 853-856 ◽  
Author(s):  
Duk Young Jung ◽  
Yu Bong Kang ◽  
Toshie Tsuchiya ◽  
Sadami Tsutsumi
Keyword(s):  
Mechanical Properties ◽  
Bulk Modulus ◽  
Soft Tissues ◽  
Articular Chondrocytes ◽  
Collagen Gel ◽  
Accuracy And Precision ◽  
Novel Method ◽  
Silicone Rubbers ◽  
High Degree ◽  
Non Destructive

Accurate measurement of the mechanical properties of artificial or cultivated cartilage is a major factor for determining successive regeneration of defective soft tissues. In this study, we developed a novel method that enabled the bulk modulus (k-modulus) to be measured nondestructively using the relationship between volume and pressure of living soft tissues. In order to validate this method we estimated the bulk modulus of soft silicone rubbers using our new method and a conventional method. The results showed a 5 ~ 10% difference between the results obtained with the two methods. Our method was used subsequently to measure the mechanical properties of cultivated cartilage samples (collagen gel type), that had been incubated for four weeks in the presence or absence of human articular chondrocytes (HACs). Our experiments showed that cultivated cartilage tissues grown in the presence of HACs had a higher bulk modulus (120 ± 20 kPa) than samples grown without HACs (90 ± 15 kPa). The results indicated that our novel method offered an effective method for measurement of volume changes in minute living soft tissues, with the measurements having a high degree of accuracy and precision. Furthermore, this method has significant advantages over conventional approaches as it can be used to rapidly and accurately evaluate the strength of soft tissues during cultivation without causing damage to the specimen.

T2-weighted Hypointense Tumors and Tumor-like Lesions

2019 ◽  
Vol 23 (01) ◽  
pp. 058-075 ◽  
Author(s):  
Amanda Isaac ◽  
Danoob Dalili ◽  
Iris-Melanie Noebauer-Huhmann ◽  
Olympia Papakonstantinou
Keyword(s):  
Soft Tissues ◽  
Fibrous Tissue ◽  
Focal Lesions ◽  
Everyday Clinical Practice ◽  
Musculoskeletal Tumors ◽  
Imaging Sequence ◽  
Sequence Selection ◽  
Tumor Like Lesions ◽  
Synovial Disorders ◽  
Hemosiderin Deposits

AbstractMost musculoskeletal tumors are hyperintense on T2-weighted images. However, some T2-weighted hypointense tumors and tumor-like lesions are encountered in everyday clinical practice. We explore the spectrum of such T2 hypointense tumors and tumor mimickers that can arise from (1) the bones, presenting as diffuse processes or focal lesions; (2) the joints including diffuse or focal synovial disorders, loose bodies, or substance depositions; and (3) soft tissues, comprising T2 hypointense tumors and tumor mimickers (those that contain abundant fibrous tissue, mineralization, or hemosiderin deposits). Appropriate magnetic resonance imaging sequence selection is required to identify and characterize these lesions confidently when imaging musculoskeletal tumors.

The yield behaviour of mild steel in dynamic compression

1956 ◽  
Vol 236 (1204) ◽  
pp. 24-40 ◽  
Keyword(s):  
Mild Steel ◽  
Impact Load ◽  
Dynamic Compression ◽  
Steel Specimen ◽  
Dynamic Strain ◽  
Compression Tests ◽  
Static Compression ◽  
Yield Phenomena ◽  
Stress Strain Relation ◽  
Yield Behaviour

Results of earlier investigations of dynamic yield phenomena are reviewed. Experiments are described in which a mild steel specimen is subjected a to compressive impact load causing yield in 25 to 30 μs . Stress-time curves are obtained and analyzed in terms of wave propagation, and a dynamic stress-strain relation is derived. Micrographs of specimens after dynamic yielding show that coarse slip does not occur, though there is some evidence of fine slip and grain boundary movement. Static compression tests on dynamically yielded specimens show that less hardening is caused by dynamic strain than by the same amount of static strain. The results are discussed in terms of dislocation theory.

Rare proliferative and inflammatory pathologies localized in the temporal bone - a review of the literature

2019 ◽  
Vol 8 (2) ◽  
pp. 1-5
Author(s):  
Adam Roszkowski Roszkowski ◽  
Alicja Witkowska ◽  
Piotr Baranek ◽  
Anna Rzepakowska ◽  
Emilia Wnuk ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Fibrous Dysplasia ◽  
Temporal Bone ◽  
Inflammatory Pseudotumor ◽  
Soft Tissues ◽  
Bone Structure ◽  
Histopathological Examination ◽  
Fibrous Tissue ◽  
Diagnostic Methods ◽  
Unknown Etiology

Proliferative-inflammatory pathologies may occupy the temporal bone, resulting in: hearing loss, vestibular dysfunction, and neuropathies from cranial nerve compression. Although their occurrence is episodic, the appropriate diagnostic procedure is extremely important to achieve expected therapeutic effect. The aim of study was characterization of selected proliferative-inflammatory pathologies that may occupy the temporal bone: fibrous dysplasia, inflammatory pseudotumor, osteoradionecrosis, and presentation of diagnostic methods for the differentiation of these diseases as well as discussion on appropriate therapeutic options. Fibrous dysplasia (fibrous dysplasia) is a slowly progressive, benign bone disorder of unknown etiology characterized by abnormal proliferation of fibrous tissue. IPT (inflammatory pseudotumor) is a rare, non-malignant inflammatory process of unknown etiology, characterized by connective tissue proliferation and infiltration of inflammatory cells. Osteoradionecrosis of the temporal bone (TB-ORN) is a rare but potentially fatal complication of radiotherapy for head and neck cancer. Due to the similarity of symptoms with typical inflammatory conditions of middle ear (pain, otorrhea, hearing loss), selected disorders may be a dilemma regarding the diagnosis and proper further treatment. The clinical examination is mandatory, however radiological imaging may demonstrate the existence of specific changes and direct the diagnosis. The computed tomography of fibrous dysplasia shows the abnormal organization of the bone structure. Magnetic resonance, as the most sensitive for inflammatory pseudotumors, visualizes inflammatory infiltrates in soft tissues. The spiral tomography of temporal identifies the erosion in the course of osteoradionecrosis. However the final diagnosis may be establish post the histopathological examination and exclusion of the neoplastic process.

MECHANICAL BEHAVIOR UNDER UNCONFINED COMPRESSION LOADINGS OF DENSE FIBRILLAR COLLAGEN MATRICES MIMETIC OF LIVING TISSUES

2010 ◽  
Vol 10 (01) ◽  
pp. 35-55 ◽  
Author(s):  
SALAH RAMTANI ◽  
YOSHIYUKI TAKAHASHI-IÑIGUEZ ◽  
CHRISTOPHE HELARY ◽  
DIDIER GEIGER ◽  
MARIE MADELEINE GIRAUD GUILLE
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Three Dimensional ◽  
Fibrillar Collagen ◽  
Unconfined Compression ◽  
Collagen Scaffolds ◽  
Collagen Concentration ◽  
Collagen Matrices ◽  
Compression Load ◽  
Living Tissues

Bio-artificial tissues are being developed as replacements for damaged biologic tissues and their mechanical properties are critical for load-bearing applications. Reconstituted dense three-dimensional (3D) fibrillar collagen matrices are promising materials for tissue engineering, at the light of their interaction with fibroblasts.1,2 The mechanical properties of these fibrillar collagen matrices are now being characterized under unconfined compression loading for various strain rates and collagen concentrations. The data were compared to those obtained in the same conditions with a biological tissue, the rat dermis. The results show a very sensitive behavior to both the displacement rate, typical of biological soft tissues, and the collagen concentration varying between 5 and 40 mg/ml. The link between the mechanical properties and the microscopic structure of the collagen scaffolds show an increasing viscoelastic modulus with respect to the fibril density. It is found that the matrices at 5 mg/ml and the dorsal rat skin (DRS) exhibit similar stress–strain response when submitted to the same external unconfined compression load. Such results highlight the interest of these matrices as potential tissue substitutes.

scholarly journals Racemization and isomerization of type I collagen C-telopeptides in human bone and soft tissues: assessment of tissue turnover

2000 ◽  
Vol 345 (3) ◽  
pp. 481-485 ◽  
Author(s):  
Evelyne GINEYTS ◽  
Paul A. C. CLOOS ◽  
Olivier BOREL ◽  
Laurent GRIMAUD ◽  
Pierre D. DELMAS ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Type I Collagen ◽  
Soft Tissues ◽  
Systematic Evaluation ◽  
Specific Marker ◽  
Type I ◽  
Aspartic Acid Residue ◽  
Post Translational Modifications ◽  
High Degree

Urinary excretion of the type I collagen C-telopeptide (CTx) has been shown to be a sensitive index of the rate of bone resorption. The human type I collagen sequence A1209HDGGR1214 of CTx can undergo racemization of the aspartic acid residue Asp1211 and isomerization of the bond between this residue and Gly1212. These spontaneous non-enzymic chemical reactions takes place in vivo in bone, and the degree of racemization and isomerization of CTx molecules may be an index of the biological age and the remodelling of bone. The aim of the present study was to investigate the degree of racemization and isomerization of type I collagen in human connective soft tissues, in order to estimate the rate of collagen turnover in adult tissues and compare it with that of bone. We also performed a systematic evaluation of the pyridinium cross-link content in adult human tissues. Using antibodies raised against the different CTx forms, we found that bone and dermis are the tissues that show most racemization and isomerization. The type I collagen of arteries, lung, intestine, kidney, skeletal muscle and heart shows significantly less racemization and isomerization than that of bone, suggesting that these soft tissues have a faster turnover than bone. We also found that pyridinoline and, to a lesser degree, deoxypyridinoline are distributed throughout the different tissues investigated. Because bone type I collagen is characterized by a high degree of both racemization/isomerization and deoxypyridinoline cross-linking, the concomitant assessment of these two post-translational modifications is likely to result in a highly specific marker of bone resorption.

A Priori Assessment of Adipose Tissue Mechanical Testing by Global Sensitivity Analysis

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Hosein Naseri ◽  
Håkan Johansson
Keyword(s):  
Sensitivity Analysis ◽  
Adipose Tissue ◽  
Soft Tissues ◽  
Global Sensitivity Analysis ◽  
A Priori ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Material Parameters ◽  
Global Sensitivity ◽  
Indentation Tests

In modeling the mechanical behavior of soft tissues, the proper choice of an experiment for identifying material parameters is not an easy task. In this study, a finite element computational framework is used to virtually simulate and assess commonly used experimental setups: rotational rheometer tests, confined- and unconfined-compression tests, and indentation tests. Variance-based global sensitivity analysis is employed to identify which parameters in different experimental setups govern model prediction and are thus more likely to be determined through parameter identification processes. Therefore, a priori assessment of experimental setups provides a base for systematic and reliable parameter identification. It is found that in indentation tests and unconfined-compression tests, incompressibility of soft tissues (adipose tissue in this study) plays an important role at high strain rates. That means bulk stiffness constitutes the main part of the mechanism of tissue response; thus, these experimental setups may not be appropriate for identifying shear stiffness. Also, identified material parameters through loading–unloading shear tests at a certain rate might not be reliable for other rates, since adipose tissue shows highly strain rate dependent behavior. Frequency sweep tests at a wide-enough frequency range seem to be the best setup to capture the strain rate behavior. Moreover, analyzing the sensitivity of model parameters in the different experimental setups provides further insight about the model itself.

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