A Recruitment Model of Tendon Viscoelasticity That Incorporates Fibril Creep and Explains Strain-Dependent Relaxation

Shearer, Tom; Parnell, William J.; Lynch, Barbara; Screen, Hazel R. C.; Abrahams, I. David

doi:10.1115/1.4045662

Cited by 19 publications

(13 citation statements)

References 63 publications

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“…There is a crucial strain associated with each fiber tissue (corresponding to its length). The nerve fibers change their elasticity only when they are taut [ 34 ]. No more elastic strain occurred when the extension reached a yield point.…”

Section: Discussionmentioning

confidence: 99%

Quantifying the Elasticity Properties of the Median Nerve during the Upper Limb Neurodynamic Test 1

Lin

Chen

Deng

et al. 2022

Applied Bionics and Biomechanics

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Background. The upper limb neurodynamic test 1 (ULNT1) consists of a series of movements that are thought to detect an increase in neuromechanical sensitivity. In vivo, no trail was made to quantify the association between the nerve elasticity and different limb postures during ULNT1. Objectives. (1) To investigate the relationship between nerve elasticity and limb postures during ULNT1 and (2) to investigate the intra- and interoperator reliabilities of shear wave elastography (SWE) in quantifying the elasticity of median nerve. Methods. Twenty healthy subjects (mean age: 19.9 ± 1.4 years old) participated in this study. The median nerve was imaged during elbow extension in the following postures: (1) with neutral posture, (2) with wrist extension (WE), (3) with contralateral cervical flexion (CCF), and (4) with both WE and CCF. The intra- and interoperator reliabilities measured by two operators at NP and CCF+WE and intraclass correlation coefficients (ICCs) were calculated. Results. The intraoperator ( ICC = 0.72 – 0.75 ) and interoperator ( ICC = 0.89 – 0.94 ) reliabilities for measuring the elasticity of the median nerve ranged from good to excellent. The mean shear modulus of the median nerve increased by 53.68% from NP to WE+CCF. Conclusion. SWE is a reliable tool to quantify the elasticity of the median nerve. There was acute modulation in the elasticity of the median nerve during the ULNT1 when healthy participants reported substantial discomfort. Further studies need to focus on the elasticity properties of the median nerve in patients with peripheral neuropathic pain.

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Section: Discussionmentioning

confidence: 99%

Quantifying the Elasticity Properties of the Median Nerve during the Upper Limb Neurodynamic Test 1

Lin

Chen

Deng

et al. 2022

Applied Bionics and Biomechanics

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“…maintain a constant level of strain) for a certain time and measure the resulting stress curve. For most soft tissues, the measured stress relaxation curve has a decaying exponential behaviour [4,5,6].…”

Section: Rheological Models For the Relaxation Functionmentioning

confidence: 99%

“…For many soft tissues the stress-relaxation curve has a decaying exponential form. Stress relaxation has been observed in the brain [2,3], in ligaments and tendons [5,6] and in the skin [15]. At the microscale, the physical mechanisms behind stress relaxation differ from tissue to tissue.…”

Section: Introductionmentioning

confidence: 99%

Foundations of viscoelasticity and application to soft tissues mechanics

Righi¹,

Balbi²

2021

Preprint

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Soft tissues are complex media, they display a wide range of mechanical properties such as anisotropy and non-linear stress-strain behaviour. They undergo large deformations and they exhibit a time-dependent mechanical behaviour, i.e. they are viscoelastic. In this chapter we review the foundations of the linear viscoelastic theory and the theory of Quasi-Linear Viscoelasticity (QLV) in view of developing new methods to estimate the viscoelastic properties of soft tissues through model fitting. To this aim, we consider the simple torsion of a viscoelastic Mooney-Rivlin material in two different testing scenarios: step-strain and ramp tests. These tests are commonly performed to characterise the time-dependent properties of soft tissues and allow to investigate their stress relaxation behaviour. Moreover, commercial torsional rheometers measure both the torque and the normal force, giving access to two sets of data. We show that for a step test, the linear and the QLV models predict the same relaxation curves for the torque. However, when the strain history is in the form of a ramp function, the non-linear terms appearing in the QLV model affect the relaxation curve of the torque depending on the final strain level and on the rising time of the ramp. Furthermore, our results show that the relaxation curve of the normal force predicted by the QLV theory depends on the level of strain both for a step and a ramp tests. To quantify the effect of the non-linear terms, we evaluate the maximum and the equilibrium (as 𝑡 → ∞) values of the relaxation curves. Our results provide useful guidelines to accurately fit QLV models in view of estimating the viscoelastic properties of soft tissues.

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“…Whilst these models are capable of predicting the general behaviour of tendons stretched to failure, they are all phenomenological to some degree and, consequently, they contain parameters that cannot be directly measured. Other models have used a microstructural approach, but were limited to modelling regions I and II of the stress-strain curve [19,20,21].…”

Section: II Iiimentioning

confidence: 99%

A microstructural model of tendon failure

Gregory¹,

Shearer²,

Hazel³

2021

Preprint

Self Cite

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Collagen fibrils are the most important structural component of tendons. Their crimped structure and parallel arrangement within the tendon lead to a distinctive non-linear stress-strain curve when a tendon is stretched. Microstructural models can be used to relate microscale collagen fibril mechanics to macroscale tendon mechanics, allowing us to identify the mechanisms behind each feature present in the stress-strain curve. Most models in the literature focus on the elastic behaviour of the tendon, and there are few which model beyond the elastic limit without introducing phenomenological parameters. We develop a model, built upon a collagen recruitment approach, that only contains microstructural parameters. We split the stress in the fibrils into elastic and plastic parts, and assume that the fibril yield stretch and rupture stretch are each described by a distribution function, rather than being single-valued. By changing the shapes of the distributions and their regions of overlap, we can produce macroscale tendon stress-strain curves that generate the full range of features observed experimentally, including those that could not be explained using existing models. These features include second linear regions occurring after the tendon has yielded, and step-like failure behaviour present after the stress has peaked. When we compare with an existing model, we find that our model reduces the average root mean squared error from 4.15MPa to 1.61MPa, and the resulting parameter values are closer to those found experimentally. Since our model contains only parameters that have a direct physical interpretation, it can be used to predict how processes such as ageing, disease, and injury affect the mechanical behaviour of tendons, provided we can quantify the effects of these processes on the microstructure.

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A Recruitment Model of Tendon Viscoelasticity That Incorporates Fibril Creep and Explains Strain-Dependent Relaxation

Cited by 19 publications

References 63 publications

Quantifying the Elasticity Properties of the Median Nerve during the Upper Limb Neurodynamic Test 1

Quantifying the Elasticity Properties of the Median Nerve during the Upper Limb Neurodynamic Test 1

Foundations of viscoelasticity and application to soft tissues mechanics

A microstructural model of tendon failure

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