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Barsimantov J, Payne J, de Lucio M, Hakim M, Gomez H, Solorio L, Tepole AB. Poroelastic Characterization and Modeling of Subcutaneous Tissue Under Confined Compression. Ann Biomed Eng 2024; 52:1638-1652. [PMID: 38472602 DOI: 10.1007/s10439-024-03477-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 02/17/2024] [Indexed: 03/14/2024]
Abstract
Subcutaneous tissue mechanics are important for drug delivery. Yet, even though this material is poroelastic, its mechanical characterization has focused on its hyperelastic response. Moreover, advancement in subcutaneous drug delivery requires effective tissue mimics such as hydrogels for which similar gaps of poroelastic data exist. Porcine subcutaneous samples and gelatin hydrogels were tested under confined compression at physiological conditions and strain rates of 0.01%/s in 5% strain steps with 2600 s of stress relaxation between loading steps. Force-time data were used in an inverse finite element approach to obtain material parameters. Tissues and gels were modeled as porous neo-Hookean materials with properties specified via shear modulus, effective solid volume fraction, initial hydraulic permeability, permeability exponent, and normalized viscous relaxation moduli. The constitutive model was implemented into an isogeometric analysis (IGA) framework to study subcutaneous injection. Subcutaneous tissue exhibited an initial spike in stress due to compression of the solid and fluid pressure buildup, with rapid relaxation explained by fluid drainage, and longer time-scale relaxation explained by viscous dissipation. The inferred parameters aligned with the ranges reported in the literature. Hydraulic permeability, the most important parameter for drug delivery, was in the rangek 0 ∈ [ 0.142 , 0.203 ] mm4 /(N s). With these parameters, IGA simulations showed peak stresses due to a 1-mL injection to reach 48.8 kPa at the site of injection, decaying after drug volume disperses into the tissue. The poro-hyper-viscoelastic neo-Hookean model captures the confined compression response of subcutaneous tissue and gelatin hydrogels. IGA implementation enables predictive simulations of drug delivery.
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Affiliation(s)
- Jacques Barsimantov
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Jordanna Payne
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
- Indiana University School of Medicine, Indianapolis, IN, USA
| | - Mario de Lucio
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Mazin Hakim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Hector Gomez
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Luis Solorio
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Adrian B Tepole
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
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Barsimantov Mandel J, Solorio L, Tepole AB. Geometry of adipocyte packing in subcutaneous tissue contributes to nonlinear tissue properties captured through a Gaussian process surrogate model. Soft Matter 2024. [PMID: 38477130 DOI: 10.1039/d3sm01661g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
Subcutaneous tissue mechanical response is governed by the geometry and mechanical properties at the microscale and drives physiological and clinical processes such as drug delivery. Even though adipocyte packing is known to change with age, disease, and from one individual to another, the link between the geometry of the packing and the overall mechanical response of adipose tissue remains poorly understood. Here we create 1200 periodic representative volume elements (RVEs) that sample the possible space of Laguerre packings describing adipose tissue. RVE mechanics are modeled under tri-axial loading. Equilibrium configuration of RVEs is solved by minimizing an energetic potential that includes volume change contributions from adipocyte expansion, and area change contributions from collagen foam stretching. The resulting mechanical response across all RVE samples is interpolated with the aid of a Gaussian process (GP), revealing how the microscale geometry dictates the overall RVE mechanics. For example, increase in adipocyte size and increase in sphericity lead to adipose tissue softening. We showcase the use of the homogenized model in finite element simulations of drug injection by implementing a Blatz-Ko model, informed by the GP, as a custom material in the popular open-source package FEBio. These simulations show how microscale geometry can lead to vastly different injection dynamics even if the constituent parameters are held constant, highlighting the importance of characterizing individual's adipose tissue structure in the development of personalized therapies.
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Affiliation(s)
| | - Luis Solorio
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, USA
| | - Adrian Buganza Tepole
- School of Mechanical Engineering, Purdue University, 205 Gates Rd, West Lafayette, USA.
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, USA
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Staples ASM, Poulsen M, Præstmark KAF, Sparre T, Sand Traberg M. The Needle Shield Size and Applied Force of Subcutaneous Autoinjectors Significantly Influence the Injection Depth. J Diabetes Sci Technol 2024:19322968241231996. [PMID: 38388411 DOI: 10.1177/19322968241231996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
BACKGROUND This study examines how shield-triggered autoinjectors (AIs), for subcutaneous drug delivery, affect injection depth. It focuses on shield size and applied force, parameters that could potentially lead to inadvertent intramuscular (IM) injections due to tissue compression. METHOD A blinded ex-vivo study was performed to assess the impact of shield size and applied force on injection depth. Shields of 15, 20, and 30 mm diameters and forces from 2 to 10 N were investigated. The study involved 55 injections in three Landrace, Yorkshire, and Duroc (LYD) pigs, with injection depths measured with computed tomography (CT). An in-vivo study, involving 20 injections in three LYD pigs, controlled the findings, using fluoroscopy (FS) videos for depth measurement. RESULTS The CT study revealed that smaller shield sizes significantly increased injection depth. With a 15 mm diameter shield, 10 N applied force, and 5 mm needle protrusion, the injection depth exceeded the needle length by over 3 mm. Injection depth increased with higher applied forces until a plateau was reached around 8 N. Both applied force and size were significant factors for injection depth (analysis of variance [ANOVA], P < .05) in the CT study. The FS study confirmed the ex-vivo findings in an in-vivo setting. CONCLUSIONS The study demonstrates that shield size has a greater impact on injection depth than the applied force. While conducted in porcine tissue, the study provides useful insights into the relative effects of shield size and applied force. Further investigations in humans are needed to confirm the predicted injection depths for AIs.
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Affiliation(s)
- Anne-Sofie Madsen Staples
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk A/S, Device and Delivery Solutions, Hillerød, Denmark
| | - Mette Poulsen
- Novo Nordisk A/S, Device and Delivery Solutions, Hillerød, Denmark
| | | | | | - Marie Sand Traberg
- Novo Nordisk A/S, Device and Delivery Solutions, Hillerød, Denmark
- Department of Health Technology Ultrasound and Biomechanics, Technical University of Denmark, Kongens Lyngby, Denmark
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Kho ASK, Béguin S, O'Cearbhaill ED, Ní Annaidh A. Mechanical characterisation of commercial artificial skin models. J Mech Behav Biomed Mater 2023; 147:106090. [PMID: 37717289 DOI: 10.1016/j.jmbbm.2023.106090] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/19/2023] [Accepted: 08/23/2023] [Indexed: 09/19/2023]
Abstract
Understanding of the mechanical properties of skin is crucial in evaluating the performance of skin-interfacing medical devices. Artificial skin models (ASMs) have rapidly gained attention as they are able to overcome the challenges in ethically sourcing consistent and representative ex vivo animal or human tissue models. Although some ASMs have become commercialised, a thorough understanding of the mechanical properties of the skin models is crucial to ensure that they are suitable for the purpose of the study. In the present study, skin and fat layers of ASMs (Simulab®, LifeLike®, SynDaver® and Parafilm®) were mechanically characterised through hardness, needle insertion, tensile and compression testing. Different boundary constraint conditions (minimally and highly constrained) were investigated for needle insertion testing, while anisotropic properties of the skin models were investigated through different specimen orientations during tensile testing. Analysis of variance (ANOVA) tests were performed to compare the mechanical properties between the skin models. Properties of the skin models were compared against literature to determine the suitability of the skin models based on the material property of interest. All skin models offer relatively consistent mechanical performance, providing a solid basis for benchtop evaluation of skin-interfacing medical device performance. Through prioritising models with mechanical properties that are consistent with human skin data, and with limited variance, researchers can use the data presented here as a toolbox to select the most appropriate ASM for their particular application.
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Affiliation(s)
- Antony S K Kho
- UCD Centre for Biomedical Engineering, University College Dublin, Belfield Dublin 4, Ireland; I-Form Advanced Manufacturing Research Centre, School of Mechanical & Materials Engineering, University College Dublin, Belfield Dublin 4, Ireland; BD Research Centre Ireland Ltd, Carysfort Avenue, Blackrock, Ireland
| | - Steve Béguin
- BD Research Centre Ireland Ltd, Carysfort Avenue, Blackrock, Ireland
| | - Eoin D O'Cearbhaill
- UCD Centre for Biomedical Engineering, University College Dublin, Belfield Dublin 4, Ireland; I-Form Advanced Manufacturing Research Centre, School of Mechanical & Materials Engineering, University College Dublin, Belfield Dublin 4, Ireland; UCD Charles Institute of Dermatology, School of Medicine, University College Dublin, Belfield Dublin 4, Ireland; The Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
| | - Aisling Ní Annaidh
- UCD Centre for Biomedical Engineering, University College Dublin, Belfield Dublin 4, Ireland; I-Form Advanced Manufacturing Research Centre, School of Mechanical & Materials Engineering, University College Dublin, Belfield Dublin 4, Ireland; UCD Charles Institute of Dermatology, School of Medicine, University College Dublin, Belfield Dublin 4, Ireland.
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Hatt A, Lloyd R, Bolsterlee B, Bilston LE. Strain-dependent shear properties of human adipose tissue in vivo. J Mech Behav Biomed Mater 2023; 143:105924. [PMID: 37276651 DOI: 10.1016/j.jmbbm.2023.105924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/14/2023] [Accepted: 05/20/2023] [Indexed: 06/07/2023]
Abstract
INTRODUCTION Human adipose tissue (fat) deforms substantially under normal physiological loading and during impact. Thus, accurate data on strain-dependent stiffness of fat is essential for the creation of accurate biomechanical models. Previous studies on ex vivo samples reported human fat to be nonlinear and viscoelastic. When static compression is combined with magnetic resonance (MR) elastography (an imaging technique used to measure viscoelasticity in vivo), the large deformation properties of tissues can be determined. Here, we use magnetic resonance elastography to quantify fat shear modulus in vivo under increasing compressive strain and compare it to the underlying passive gluteal muscle. METHODS The right buttocks of ten female participants were incrementally compressed at four levels while MR elastography (50 Hz) and mDixon images were acquired. Maps of tissue shear modulus (G*) were reconstructed from the MR elastography phase images. Tissue strain was estimated from registration of deformed and undeformed mDixon images. Linear mixed models were fit to the natural logarithm of the compressive strain and shear modulus data for each tissue. RESULTS Shear modulus increased in an exponential relationship with compressive strain in fat: Gfat*=748.5*Cyy-1.18Pa, and to a lesser extent in muscle: Gmuscle*=956.4*Cyy-0.36Pa. The baseline (undeformed) stiffness of fat was significantly lower than that of muscle (mean G*fat = 752 Pa, mean G*muscle = 1000 Pa, paired samples t-test, t = -4.24, p = 0.001). However, fat exhibited a significantly higher degree of strain dependence (characterised by the exponent of the curve, t = -6.47, p = 0.0001). CONCLUSION Static compression of human adipose tissue results in an increase in apparent viscoelastic shear modulus (stiffness), in an exponentially increasing relationship. The relationships defined here can be used in the development of physiologically realistic computational models for impact, injury and biomechanical modelling.
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Affiliation(s)
- Alice Hatt
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia
| | - Robert Lloyd
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia; University of New South Wales, Faculty of Medicine & Health, 18 High St, Kensington, NSW, 2052, Australia
| | - Bart Bolsterlee
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia; University of New South Wales, Graduate School of Biomedical Engineering, Library Rd, Kensington, NSW, 2033, Australia
| | - Lynne E Bilston
- Neuroscience Research Australia, PO Box 1165, Randwick, NSW, 2031, Australia; University of New South Wales, Faculty of Medicine & Health, 18 High St, Kensington, NSW, 2052, Australia.
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Roblin NV, DeBari MK, Shefter SL, Iizuka E, Abbott RD. Development of a More Environmentally Friendly Silk Fibroin Scaffold for Soft Tissue Applications. J Funct Biomater 2023; 14:jfb14040230. [PMID: 37103320 PMCID: PMC10143335 DOI: 10.3390/jfb14040230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/12/2023] [Accepted: 04/14/2023] [Indexed: 04/28/2023] Open
Abstract
A push for environmentally friendly approaches to biomaterials fabrication has emerged from growing conservational concerns in recent years. Different stages in silk fibroin scaffold production, including sodium carbonate (Na2CO3)-based degumming and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)-based fabrication, have drawn attention for their associated environmental concerns. Environmentally friendly alternatives have been proposed for each processing stage; however, an integrated green fibroin scaffold approach has not been characterized or used for soft tissue applications. Here, we show that the combination of sodium hydroxide (NaOH) as a substitute degumming agent with the popular "aqueous-based" alternative silk fibroin gelation method yields fibroin scaffolds with comparable properties to traditional Na2CO3-degummed aqueous-based scaffolds. The more environmentally friendly scaffolds were found to have comparable protein structure, morphology, compressive modulus, and degradation kinetics, with increased porosity and cell seeding density relative to traditional scaffolds. Human adipose-derived stem cells showed high viability after three days of culture while seeded in each scaffold type, with uniform cell attachment to pore walls. Adipocytes from human whole adipose tissue seeded into scaffolds were found to have similar levels of lipolytic and metabolic function between conditions, in addition to a healthy unilocular morphology. Results indicate that our more environmentally friendly methodology for silk scaffold production is a viable alternative and well suited to soft tissue applications.
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Affiliation(s)
- Nathan V Roblin
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Megan K DeBari
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Sandra L Shefter
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Erica Iizuka
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Rosalyn D Abbott
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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Teixeira AM, Martins P. A review of bioengineering techniques applied to breast tissue: Mechanical properties, tissue engineering and finite element analysis. Front Bioeng Biotechnol 2023; 11:1161815. [PMID: 37077233 PMCID: PMC10106631 DOI: 10.3389/fbioe.2023.1161815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 03/14/2023] [Indexed: 04/05/2023] Open
Abstract
Female breast cancer was the most prevalent cancer worldwide in 2020, according to the Global Cancer Observatory. As a prophylactic measure or as a treatment, mastectomy and lumpectomy are often performed at women. Following these surgeries, women normally do a breast reconstruction to minimize the impact on their physical appearance and, hence, on their mental health, associated with self-image issues. Nowadays, breast reconstruction is based on autologous tissues or implants, which both have disadvantages, such as volume loss over time or capsular contracture, respectively. Tissue engineering and regenerative medicine can bring better solutions and overcome these current limitations. Even though more knowledge needs to be acquired, the combination of biomaterial scaffolds and autologous cells appears to be a promising approach for breast reconstruction. With the growth and improvement of additive manufacturing, three dimensional (3D) printing has been demonstrating a lot of potential to produce complex scaffolds with high resolution. Natural and synthetic materials have been studied in this context and seeded mainly with adipose derived stem cells (ADSCs) since they have a high capability of differentiation. The scaffold must mimic the environment of the extracellular matrix (ECM) of the native tissue, being a structural support for cells to adhere, proliferate and migrate. Hydrogels (e.g., gelatin, alginate, collagen, and fibrin) have been a biomaterial widely studied for this purpose since their matrix resembles the natural ECM of the native tissues. A powerful tool that can be used in parallel with experimental techniques is finite element (FE) modeling, which can aid the measurement of mechanical properties of either breast tissues or scaffolds. FE models may help in the simulation of the whole breast or scaffold under different conditions, predicting what might happen in real life. Therefore, this review gives an overall summary concerning the human breast, specifically its mechanical properties using experimental and FE analysis, and the tissue engineering approaches to regenerate this particular tissue, along with FE models.
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Affiliation(s)
| | - Pedro Martins
- UBS, INEGI, LAETA, Porto, Portugal
- I3A, Universidad de Zaragoza, Zaragoza, Spain
- *Correspondence: Pedro Martins,
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Horgan CO, Murphy JG. Exponents of the one-term Ogden model: insights from simple shear. Philos Trans A Math Phys Eng Sci 2022; 380:20210328. [PMID: 36031831 PMCID: PMC9421378 DOI: 10.1098/rsta.2021.0328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 01/27/2022] [Indexed: 06/15/2023]
Abstract
Isotropic one-term Ogden models are widely used to predict the mechanical response of both incompressible elastomers and soft tissue. Even though the exponent might be chosen to yield excellent agreement with some aspects of mechanical response, there is no guarantee that these models will be physically realistic in all situations. We show here that, in particular, the predictions of models with either negative or large positive exponents do not seem physically realistic in simple shear. The mechanical response of materials in shear should be physically realistic to ensure rational and reliable predictions for complex geometries and boundary conditions. We suggest that for problematic values of exponents of one-term models that extra Ogden invariants should necessarily be included in the model. This article is part of the theme issue 'The Ogden model of rubber mechanics: Fifty years of impact on nonlinear elasticity'.
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Affiliation(s)
- Cornelius O. Horgan
- School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904, USA
| | - Jeremiah G. Murphy
- Department of Mechanical Engineering, Dublin City University, Glasnevin, Dublin D09 W6Y4, Ireland
- School of Mathematics, Statistics and Applied Mathematics, National University of Ireland Galway, University Road, Galway, Ireland
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Fontanella CG, Toniolo I, Foletto M, Prevedello L, Carniel EL. Mechanical Behavior of Subcutaneous and Visceral Abdominal Adipose Tissue in Patients with Obesity. Processes (Basel) 2022; 10:1798. [DOI: 10.3390/pr10091798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The mechanical characterization of adipose tissues is important for various medical purposes, including plastic surgery and biomechanical applications, such as computational human body models for the simulation of surgical procedures or injury prediction, for example, in the evaluation of vehicle crashworthiness. In this context, the measurement of human subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) mechanical properties in relation to subject characteristics may be really relevant. The aim of this work was to properly characterize the mechanical response of adipose tissues in patients with obesity. Then, the data were exploited to develop a reliable finite element model of the adipose tissues characterized by a constitutive material model that accounted for nonlinear elasticity and time dependence. Mechanical tests have been performed on both SAT and VAT specimens, which have been harvested from patients with severe obesity during standard laparoscopic sleeve gastrectomy intervention. The experimental campaign included indentation tests, which permitted us to obtain the initial/final indentation stiffnesses for each specimen. Statistical results revealed a higher statistical stiffness in SAT than in VAT, with an initial/final indentation stiffness of 1.65 (SD ± 0.29) N/30.30 (SD ± 20) N compared to 1.29 (SD ± 0.30) N/21.00 (SD ± 16) N. Moreover, the results showed that gender, BMI, and age did not significantly affect the stiffness. The experimental results were used in the identification of the constitutive parameters to be inserted in the constitutive material model. Such constitutive characterization of VAT and SAT mechanics can be the starting point for the future development of more accurate computational models of the human adipose tissue and, in general, of the human body for the optimization of numerous medical and biomechanical procedures and applications.
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Fontanella CG, Belluzzi E, Pozzuoli A, Favero M, Ruggieri P, Macchi V, Carniel EL. Mechanical behavior of infrapatellar fat pad of patients affected by osteoarthritis. J Biomech 2021; 131:110931. [PMID: 34972018 DOI: 10.1016/j.jbiomech.2021.110931] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/19/2021] [Accepted: 12/19/2021] [Indexed: 01/14/2023]
Abstract
The infrapatellar fat pad (IFP) is an adipose tissue present in the knee that lies between the patella, femur, meniscus and tibia, filling the space between these structures. IFP facilitates the distribution of the synovial fluid and may act to absorb impulsive actions generated through the joint. IFP in osteoarthritis (OA) pathology undergoes structural changes characterized by inflammation, hypertrophy and fibrosis. The aim of the present study is to analyze the mechanical behavior of the IFP in patients affected by end-stage OA. A specific test fixture was designed and indentation tests were performed on IFP specimens harvested from OA patients who underwent total knee arthroplasty. Experiments allowed to assess the typical features of mechanical response, such as non-linear stress-strain behavior and time-dependent effects. Results from mechanical experimentations were implemented within the framework of a visco-hyperelastic constitutive theory, with the aim to provide data for computational modelling of OA IFP role in knee mechanics. Initial and final indentation stiffness were calculated for all subjects and statistical results reveled that OA IFP mechanics was not significantly influenced by gender, BMI and sample preparation. OA IFP mechanical behavior was also compared to that of other adipose tissues. OA IFP appeared to be a stiffer adipose tissue compared to subcutaneous, visceral adipose tissues and heel fat pads. It is reasonable that fibrosis induces a modification of the tissue destabilizing the normal distribution of forces in the joint during movement, causing a worsening of the disease.
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Affiliation(s)
- Chiara Giulia Fontanella
- Department of Industrial Engineering, University of Padova, 35131 Padova, Italy; Centre for Mechanics of Biological Materials, University of Padova, 35131 Padova, Italy
| | - Elisa Belluzzi
- Musculoskeletal Pathology and Oncology Laboratory, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy; Orthopedics and Orthopedic Oncology, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy.
| | - Assunta Pozzuoli
- Musculoskeletal Pathology and Oncology Laboratory, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy; Orthopedics and Orthopedic Oncology, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy
| | - Marta Favero
- Rheumatology Unit, Department of Medicine-DIMED, University-Hospital of Padova, 35128 Padova, Italy; Internal Medicine I, Cà Foncello Hospital, 31100 Treviso, Italy
| | - Pietro Ruggieri
- Orthopedics and Orthopedic Oncology, Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padova, 35128 Padova, Italy
| | - Veronica Macchi
- Centre for Mechanics of Biological Materials, University of Padova, 35131 Padova, Italy; Department of Neurosciences, Institute of Human Anatomy, University of Padova, 35121 Padova, Italy
| | - Emanuele Luigi Carniel
- Department of Industrial Engineering, University of Padova, 35131 Padova, Italy; Centre for Mechanics of Biological Materials, University of Padova, 35131 Padova, Italy
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Lanzl F, Duddeck F, Willuweit S, Peldschus S. Experimental characterisation of porcine subcutaneous adipose tissue under blunt impact up to irreversible deformation. Int J Legal Med 2021. [PMID: 34862924 DOI: 10.1007/s00414-021-02755-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/26/2021] [Indexed: 12/04/2022]
Abstract
A deeper understanding of the mechanical characteristics of adipose tissue under large deformation is important for the analysis of blunt force trauma, as adipose tissue alters the stresses and strains that are transferred to subjacent tissues. Hence, results from drop tower tests of subcutaneous adipose tissue are presented (i) to characterise adipose tissue behaviour up to irreversible deformation, (ii) to relate this to the microstructural configuration, (iii) to quantify this deformation and (iv) to provide an analytical basis for computational modelling of adipose tissue under blunt impact. The drop tower experiments are performed exemplarily on porcine subcutaneous adipose tissue specimens for three different impact velocities and two impactor geometries. An approach based on photogrammetry is used to derive 3D representations of the deformation patterns directly after the impact. Median values for maximum impactor acceleration for tests with a flat cylindrical impactor geometry at impact velocities of 886 mm/s, 1253 mm/s and 2426 mm/s amount to 61.1 g, 121.6 g and 264.2 g, respectively, whereas thickness reduction of the specimens after impact amount to 16.7%, 30.5% and 39.3%, respectively. The according values for tests with a spherically shaped impactor at an impact velocity of 1253 mm/s are 184.2 g and 78.7%. Based on these results, it is hypothesised that, in the initial phase of a blunt impact, adipose tissue behaviour is mainly governed by the behaviour of the lipid inside the adipocytes, whereas for further loading, contribution of the extracellular collagen fibre network becomes more dominant.
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Sun Z, Gepner BD, Lee SH, Rigby J, Cottler PS, Hallman JJ, Kerrigan JR. Multidirectional mechanical properties and constitutive modeling of human adipose tissue under dynamic loading. Acta Biomater 2021; 129:188-198. [PMID: 34048975 DOI: 10.1016/j.actbio.2021.05.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 05/02/2021] [Accepted: 05/17/2021] [Indexed: 02/07/2023]
Abstract
The mechanical behavior of subcutaneous adipose tissue (SAT) affects the interaction between vehicle occupants and restraint systems in motor vehicle crashes (MVCs). To enhance future restraints, injury countermeasures, and other vehicle safety systems, computational simulations are often used to augment experiments because of their relative efficiency for parametric analysis. How well finite element human body models (FE-HBMs), which are often used in such simulations, predict human response has been limited by the absence of material models for human SAT that are applicable to the MVC environment. In this study, for the first time, dynamic multidirectional unconfined compression and simple shear loading tests were performed on human abdominal SAT specimens under conditions similar to MVCs. We also performed multiple ramp-hold tests to evaluate the quasilinear viscoelasticity (QLV) assumption and capture the stress relaxation behavior under both compression and shear. Our mechanical characterization was supplemented with scanning electron microscopy (SEM) performed in different orientations to investigate whether the macrostructural response can be related to the underlying microstructure. While the overall structure was shown to be visually different in different anatomical planes, a preferred orientation of any fibrous structures could not be identified. We showed that the nonlinear, viscoelastic, and direction-dependent responses under compression and shear tests could be captured by incorporating QLV in an Ogden-type hyperelastic model. Our comprehensive approach will lead to more accurate computational simulations and support the collective effort on the research of future occupant protection systems. STATEMENT OF SIGNIFICANCE: There is an urgent need to characterize the mechanical behavior of human adipose tissue under multiple dynamic loading conditions, and to identify constitutive models that are able to capture the tissue response under these conditions. We performed the first series of experiments on human adipose tissue specimens to characterize the multi-directional compression and shear behavior at impact loading rates and obtained scanning electron microscope images to investigate whether the macrostructural response can be related to the underlying microstructure. The results showed that human adipose tissue is nonlinear, viscoelastic and direction dependent, and its mechanical response under compression and shear tests at different loading rates can be captured by incorporating quasi-linear viscoelasticity in an Ogden-type hyperelastic model.
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Sun Z, Gepner BD, Cottler PS, Lee SH, Kerrigan JR. In Vitro Mechanical Characterization and Modeling of Subcutaneous Adipose Tissue: A Comprehensive Review. J Biomech Eng 2021; 143:1100567. [PMID: 33625495 DOI: 10.1115/1.4050286] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Indexed: 11/08/2022]
Abstract
Mechanical models of adipose tissue are important for various medical applications including cosmetics, injuries, implantable drug delivery systems, plastic surgeries, biomechanical applications such as computational human body models for surgery simulation, and blunt impact trauma prediction. This article presents a comprehensive review of in vivo experimental approaches that aimed to characterize the mechanical properties of adipose tissue, and the resulting constitutive models and model parameters identified. In particular, this study examines the material behavior of adipose tissue, including its nonlinear stress-strain relationship, viscoelasticity, strain hardening and softening, rate-sensitivity, anisotropy, preconditioning, failure behavior, and temperature dependency.
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Affiliation(s)
- Zhaonan Sun
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
| | - Bronislaw D Gepner
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
| | - Patrick S Cottler
- Department of Plastic Surgery, University of Virginia, Charlottesville, VA 22903
| | - Sang-Hyun Lee
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
| | - Jason R Kerrigan
- Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911
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