Different regions of bovine deep digital flexor tendon exhibit distinct elastic, but not viscous, mechanical properties under both compression and shear loading

Fang, Fei; Sawhney, Amrita S.; Lake, Spencer P.

doi:10.1016/j.jbiomech.2014.07.026

Cited by 28 publications

(31 citation statements)

References 23 publications

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“…Demonstrating the multiscale nature of tendon mechanics, applied strains were found to be attenuated from tissue to local matrix scale in both equine superficial digital flexor and common digital extensor tendons [15,30]. Illustrative of the multiaxial mechanical properties of tendon, our work has shown that distinct regions of bovine deep digital flexor tendon exhibit different stresses under shear and compression loading, and similar to tensile results, strains were attenuated from the tissue to nuclei scales under non-tensile deformation [6,31]. The modifications of composition and structural properties that occur across different length scales as a result of these factors certainly contribute to overall tendon mechanics and function [32][33][34].…”

Section: Motivation For Modelling Tendon Mechanicssupporting

confidence: 54%

“…For example, a component mechanical model composed of an elastic (steady-state) spring in parallel with four Maxwell components was proposed to describe tendon strain-dependent viscoelastic behaviour [55]. In our previous work, we used a two-relaxation-time solid linear model formed by two Maxwell elements and one spring in parallel to describe step strain relaxation of bovine flexor tendon [31]. In another study, a simple structural model incorporated two Kelvin models in series to represent non-fibrillar matrix and collagen fibrils, respectively, and the strain-rate dependent mechanical properties demonstrated by this model were consistent with experimental data of both normal and cross-link-deficient tendons [74].…”

Section: Mathematical Modelling On the Tissue Scale Using Phenomenolomentioning

confidence: 99%

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Modelling approaches for evaluating multiscale tendon mechanics

Fang

Lake

2016

Interface Focus.

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Tendon exhibits anisotropic, inhomogeneous and viscoelastic mechanical properties that are determined by its complicated hierarchical structure and varying amounts/organization of different tissue constituents. Although extensive research has been conducted to use modelling approaches to interpret tendon structure–function relationships in combination with experimental data, many issues remain unclear (i.e. the role of minor components such as decorin, aggrecan and elastin), and the integration of mechanical analysis across different length scales has not been well applied to explore stress or strain transfer from macro- to microscale. This review outlines mathematical and computational models that have been used to understand tendon mechanics at different scales of the hierarchical organization. Model representations at the molecular, fibril and tissue levels are discussed, including formulations that follow phenomenological and microstructural approaches (which include evaluations of crimp, helical structure and the interaction between collagen fibrils and proteoglycans). Multiscale modelling approaches incorporating tendon features are suggested to be an advantageous methodology to understand further the physiological mechanical response of tendon and corresponding adaptation of properties owing to unique in vivo loading environments.

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Section: Motivation For Modelling Tendon Mechanicssupporting

confidence: 54%

Section: Mathematical Modelling On the Tissue Scale Using Phenomenolomentioning

confidence: 99%

Modelling approaches for evaluating multiscale tendon mechanics

Fang

Lake

2016

Interface Focus.

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“…Bovine DDFTs (age 14–30 months, n = 10) were obtained from Animal Technologies, Inc. (Tyler, Texas). Thawed blocks of 2 cm length were harvested from locations 4‐cm and 2‐cm away from the natural bifurcation in order to obtain samples from the proximal and distal regions, respectively . The medial and lateral surfaces of each sample were leveled on a freezing stage (BFS‐30MP, Physitemp, Clifton, NJ) sledge microtome (Leica 1400, Buffalo Grove, IL) to ensure smooth surfaces for microscopy imaging.…”

Section: Methodsmentioning

confidence: 99%

Multiscale strain analysis of tendon subjected to shear and compression demonstrates strain attenuation, fiber sliding, and reorganization

Fang

Lake

2015

Journal Orthopaedic Research

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ABSTRACT:The manner in which strains are passed down the hierarchical length scales of tendons dictates how cells within the collagen network regulate the tissue response to loading. How tendons deform in different hierarchical levels under shear and compression is unknown. The aims of this study were: (i) to evaluate whether specific regions of bovine deep digital flexor tendons exhibited different strain attenuation from macro to micro length scales, and (ii) to elucidate mechanisms responsible for tendon deformation under shear and compression. Samples from distal and proximal regions of flexor tendons were subjected to three-step incremental stress-relaxation tests. Images of tissue markers, photobleached lines on collagen fibers, and nuclei locations were collected before and after loading. Results showed that strain transfer was attenuated from tissue to local matrix under both shear and compression. Nuclear aspect ratios exhibited smaller changes for distal samples, suggesting that cells are more shielded from deformation in the distal region. Collagen fiber sliding was observed to contribute significantly in response to shear, while uncrimping and fiber reorganization were the predominant mechanisms under compression. This study provides insight into microscale mechanisms responsible for multiscale strain attenuation of tendons under non-tensile macroscale loading. Keywords: tendon; multiscale strain transfer; shear; compression; two-photon microscopy In addition to experiencing tensile loading, tendons often function in complicated in vivo loading environments. In such cases, cell-driven alterations to the compositional and structural properties of tendons lead to mechanical properties that can vary with anatomical locations, regions within the tendon, species, and age. For example, the supraspinatus tendon (SST), one of four musculotendinous units in the rotator cuff of the shoulder, experiences shear and compressive forces as a result of the wide range of motion of the shoulder joint and complex interactions with neighboring anatomy. 1-4 As a result, specific locations of the human SST exhibit significantly different fiber alignment and tensile modulus during tensile loading, 5,6 as well as compositional differences (i.e., collagens, proteoglycans) by location. 3,7 Similarly, the bovine deep digital flexor tendon (DDFT) functions in a multiaxial physiological loading environment with forces that vary at different anatomical locations: the proximal region is mostly loaded in tension, while the distal region is also compressed against the navicular bone during normal joint function. 8-13 Our previous study, 14 which evaluated the DDFT as an easily accessible example of a complexly loaded tendon with tissue-level properties that vary by location, 8 demonstrated that the proximal and distal regions exhibited different elastic mechanical properties, yet similar viscoelastic properties, and inhomogeneous proteoglycan distribution and collagen organization.Several previous studies have explored how strains t...

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“…Although many tendons operate in the toe-region of tissue's stress–strain curve where resistance to deformation begins to increase (less than 5% of their load until rupture) [61], higher load bearing tendons, such as the Achilles, can experience forces nearly 70% of their maximum load and stress before rupture (~3500 N or ~55 MPa) [30,31]. The primary direction of loading in tendons is tensile, yet compressive, biaxial, and shear stresses may be present [62,63]. The wide variation in mechanical properties and loading environments across tendons emphasizes their dynamic role in the musculoskeletal system and the complexity of research necessary to understand their basic mechanisms of homeostasis and injury.…”

Section: Case Study 1: the Extracellular Matrix In The Tendonmentioning

confidence: 99%

The (dys)functional extracellular matrix

Freedman

Bade

Riggin

et al. 2015

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

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The extracellular matrix (ECM) is a major component of the biomechanical environment with which cells interact, and it plays important roles in both normal development and disease progression. Mechanical and biochemical factors alter the biomechanical properties of tissues by driving cellular remodeling of the ECM. This review provides an overview of the structural, compositional, and mechanical properties of the ECM that instruct cell behaviors. Case studies are reviewed that highlight mechanotransduction in the context of two distinct tissues: tendons and the heart. Although these two tissues demonstrate differences in relative cell–ECM composition and mechanical environment, they share similar mechanisms underlying ECM dysfunction and cell mechanotransduction. Together, these topics provide a framework for a fundamental understanding of the ECM and how it may vary across normal and diseased tissues in response to mechanical and biochemical cues. This article is part of a Special Issue entitled: Mechanobiology.

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Different regions of bovine deep digital flexor tendon exhibit distinct elastic, but not viscous, mechanical properties under both compression and shear loading

Cited by 28 publications

References 23 publications

Modelling approaches for evaluating multiscale tendon mechanics

Modelling approaches for evaluating multiscale tendon mechanics

Multiscale strain analysis of tendon subjected to shear and compression demonstrates strain attenuation, fiber sliding, and reorganization

The (dys)functional extracellular matrix

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