Initial estimation of the in vivo material properties of the seated human buttocks and thighs

Sadler, Zachary; Scott, Justin; Drost, Joshua P.; Chen, Sheng; Roccabianca, Sara; Bush, Tamara Reid

doi:10.1016/j.ijnonlinmec.2018.09.007

Cited by 13 publications

(9 citation statements)

References 36 publications

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“…The systematic error also suggests that, in addition to the choice of the geometric approximation of the ischial tuberosity, other factors involved in the definition and measurement of the principal shear strain in the local FE model might be lacking, their identification requiring further work. Second, the extraction of the material properties using an inverse identification method (for which the optimal parameters are obtained by minimizing the distance between experimental measures and numerical results), although popular for lower limb soft tissues (Affagard et al, 2015;Frauziols et al, 2016;Macron et al, 2018;Rohan et al, 2014;Sadler et al, 2018), is not compatible with clinical implementation because of lengthy solver times for the models and the need for a trained user to develop and interpret the FE model. Ultrasound Elastography, and, in particular, Supersonic Shear Imaging (SSI) technique, is emerging as an innovative tool that could provide a quantitative evaluation of biomechanical properties of soft tissues (Eby et al, 2013;Gennisson et al, 2010;Haen et al, 2017;Vergari et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Is a simplified Finite Element model of the gluteus region able to capture the mechanical response of the internal soft tissues under compression?

Macron

Pillet

Doridam

et al. 2020

Clinical Biomechanics

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Background: Internal soft tissue strains have been shown to be one of the main factors responsible for the onset of Pressure Ulcers and to be representative of its risk of development. However, the estimation of this parameter using Finite Element (FE) analysis in clinical setups is currently hindered by costly acquisition, reconstruction and computation times. Ultrasound (US) imaging is a promising candidate for the clinical assessment of both morphological and material parameters. Method: The aim of this study was to investigate the ability of a local FE model of the region beneath the ischium with a limited number of parameters to capture the internal response of the gluteus region predicted by a complete 3D FE model. 26 local FE models were developed, and their predictions were compared to those of the patient-specific reference FE models in sitting position. Findings: A high correlation was observed (R= 0.90, p-value < 0.01). A sensitivity analysis showed that the most influent parameters were the mechanical behaviour of the muscle tissues, the ischium morphology and the external mechanical loading. Interpretation: Given the progress of US for capturing both morphological and material parameters, these results are promising because they open up the possibility to use personalised simplified FE models for risk estimation in daily clinical routine.

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Section: Discussionmentioning

confidence: 99%

Is a simplified Finite Element model of the gluteus region able to capture the mechanical response of the internal soft tissues under compression?

Macron

Pillet

Doridam

et al. 2020

Clinical Biomechanics

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“…However, the comparison could also be intricate due to differences in areas of indentation. Reported values of material parameters of the thigh soft tissues in the literature were equivalent to a shear modulus comprised between 1 kPa and 46 kPa and no values were reported concerning the exponent parameter [17,18,39]. As far as the authors are aware of, Affagard et al were the only ones to performed inverse FE modelling on the thigh [17].…”

Section: Discussionmentioning

confidence: 99%

“…For comparison purpose, analytical identifications of fused soft tissues material parameters of the thigh are also detailed afterwards. In particular, Sadler et al estimated material parameters of the posterior thigh tissues from experimental force-deflection data at three levels: distal, proximal and middle thigh [18]. Subjects were asked to sit on a chair instrumented with an indenter and a load cell.…”

Section: Discussionmentioning

confidence: 99%

“…The personalisation of material properties is a highly challenging bottleneck for the whole community, more particularly in regions with high tissue thicknesses such as the thigh where to compute the geometry without deformation, complex image acquisition systems are often needed [15][16][17][18] One way to evaluate the mechanical behaviour of soft tissues under quasi-static compression is to perform indentation tests to collect force-displacement data [18][19][20][21][22][23]. From such measurements, the extraction of material properties is not direct.…”

Section: Introductionmentioning

confidence: 99%

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Combining Freehand Ultrasound-Based Indentation and Inverse Finite Element Modeling for the Identification of Hyperelastic Material Properties of Thigh Soft Tissues

Fougeron

Rohan

Haering

et al. 2020

Journal of Biomechanical Engineering

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Finite element analysis (FEA) is a numerical modeling tool vastly employed in research facilities to analyze and predict load transmission between the human body and a medical device, such as a prosthesis or an exoskeleton. Yet, the use of finite element modeling (FEM) in a framework compatible with clinical constraints is hindered by, among others, heavy and time-consuming assessments of material properties. Ultrasound (U.S.) imaging opens new and unique opportunities for the assessment of in vivo material properties of soft tissues. Confident of these advances, a method combining a freehand U.S. probe and a force sensor was developed in order to compute the hyperelastic constitutive parameters of the soft tissues of the thigh in both relaxed (R) and contracted (C) muscles' configurations. Seven asymptomatic subjects were included for the experiment. Two operators in each configuration performed the acquisitions. Inverse FEM allowed for the optimization of an Ogden's hyperelastic constitutive model of soft tissues of the thigh in large displacement. The mean shear modulus identified for configurations R and C was, respectively, 3.2 ± 1.3 kPa and 13.7 ± 6.5 kPa. The mean alpha parameter identified for configurations R and C was, respectively, 10 ± 1 and 9 ± 4. An analysis of variance showed that the configuration had an effect on constitutive parameters but not on the operator.

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“…First, soft tissue distribution changes with different postures, especially the soft tissue of the buttocks with the flexion of both the hips and knees, like when seated. This position change, from supine to a seated posture, results in both anatomical and mechanical changes in the soft tissue [9,[16][17][18]. Second, evaluating unloaded soft tissue in a seated position for the buttocks and thighs is difficult, given that the body needs to be balanced and suspended with minimal pressure to image soft tissue while maintaining a neutral pelvis.…”

Section: Introductionmentioning

confidence: 99%

A novel approach for quantitative imaging of the seated anatomy of the buttocks using ultrasound and MRI

Mogale,

Scott,

Schanz

et al. 2023

Front. Phys.

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Background: Pressure injuries are commonly noted in individuals who use wheelchairs for mobility and sit for prolonged periods. Understanding soft tissue composition is an essential part of treating and preventing pressure injuries. This study proposes novel approaches for imaging the soft tissue of the buttocks in unloaded and loaded conditions using ultrasound (US) and magnetic resonance imaging (MRI).Methods: The soft tissue of the buttocks was measured in able-bodied participants (n = 26, 50% female) and one male with a spinal cord injury using an innovative chair that allowed seated US acquisition of the buttocks and a newly developed MRI compatible loader. The US test–retest reliability (reproducibility) of buttocks soft tissue was assessed, and US was validated with MRI. Soft tissue was measured between the peak of the ischial tuberosity (IT) and proximal femur and the skin. MRI was used to quantify the fat fraction of the gluteus maximus muscle, with the goal of determining the influence of intramuscular fat on loaded soft tissue responses and was used to assess tissue thickness during buttocks loading.Results: US reproducibility was excellent, ICC = 0.934–0.981, with no statistical differences between scan days. Coefficients of variation (CVs) between visits ranged from 2.5% to 7.4% for loaded and unloaded tissue. US and MRI measures of tissue thickness were significantly correlated (r = 0.68–0.91, p ≤ 0.001). US underestimated the unloaded tissue thicknesses, with a mean bias of 0.39–0.56 cm. When the buttocks were loaded, US- and MRI-measured total tissue thickness was reduced by up to 64.2% ± 9.1% (p < 0.001). The US- and MRI-unloaded total soft tissue of the IT was correlated with loaded tissue thickness (r = 0.54–0.67, p ≤ 0.027). Intramuscular fat of the gluteus maximus was not correlated to changes in muscle thickness with loading (r = 0.05, p > 0.05).Conclusion: We have developed and validated a novel US methodology using MRI as a comparison measure to investigate soft tissue anatomy and deformation during sitting and loading. The ability to obtain such data in the loaded condition is unique and fills an unmet need in understanding loading and pressure injury formation.

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Initial estimation of the in vivo material properties of the seated human buttocks and thighs

Cited by 13 publications

References 36 publications

Is a simplified Finite Element model of the gluteus region able to capture the mechanical response of the internal soft tissues under compression?

Is a simplified Finite Element model of the gluteus region able to capture the mechanical response of the internal soft tissues under compression?

Combining Freehand Ultrasound-Based Indentation and Inverse Finite Element Modeling for the Identification of Hyperelastic Material Properties of Thigh Soft Tissues

A novel approach for quantitative imaging of the seated anatomy of the buttocks using ultrasound and MRI

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