研究者詳細 - 山田　宏

論文 - 山田　宏

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Stress evaluation along the posterior annular circumferential tears on the L5-S1 spinal unit as an index of tear progression 査読有り国際誌

Vinyas, Bhat, S.K., Yamada, H., Kumar, N., Adhikari, R., Bhat N, S.

Journal of Orthopaedics 67 148 - 164 2025年09月

Deformation analysis of forearm soft tissues surrounding the cephalic vein under shear on the skin surface using ultrasound video images 査読有り国際誌

H. Yamada, Y. Tanoue, S. Shimoide, M. Tanaka

Mechanical Engineering Journal 11 ( 6 ) 24-00191 2024年12月

Radial force and wire structure determine the onset of covered self-expandable metal stent migration in endoscopic ultrasound-guided hepaticogastrostomy: Measurement of sliding-resistance force using a porcine model 査読有り国際誌

T. Koga, H. Yamada, Y. Ishida, N. Tsuchiya, T. Kitaguchi, K. Matsumoto, M. Fukuyama, N. Kojima, F. Hirai

Journal of Hepato-Biliary-Pancreatic Sciences 31 ( 11 ) 840 - 849 2024年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Background: Self-expandable metal stent (SEMS) migration after endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS) is a severe complication. The migration risk could be related to the surface friction of SEMS, assumed to be affected by the wire structure and mechanical properties, including radial force (RF); however, their relevance remains unclear. This experimental study aimed to assess the mechanical properties of SEMS involved in the onset of stent migration by measuring the sliding-resistance force (SF) as the SEMS moves through the stomach wall. Methods: The SF of seven types of 8-mm diameter SEMS (four braided and three laser-cut types) and porcine stomach wall was measured with a universal testing machine. The SF of each SEMS was measured three times, and the average maximum SF (SFmax) was used for analysis. The correlation between SFmax and RF of each SEMS was evaluated. Results: SFmax and RF showed a very strong positive correlation (r = 0.92). Compared to the regression line predictions in the scatter plots of SFmax and RF, the SFmax of laser-cut and braided type SEMSs had positive and negative residuals, respectively. Conclusions: Selecting a laser-cut type SEMS with a higher RF may more effectively prevent the onset of stent migration against the stomach wall in EUS-HGS.

DOI： 10.1002/jhbp.12050

Scopus

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In-silico study on cumulative effects of degeneration and circumferential annular tear on the L5-S1 spinal unit 査読有り国際誌

Vinyas, S.K. Bhat, H. Yamada, S.N. Bhat

Biomedical Physics & Engineering Express 10 ( 6 ) 065009 2024年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

Low back pain is a serious health concern prevalent in majority of the people around the world, especially in case of the elderly. The root cause for this is mostly observed to be the development of lesions/ tears complemented by degenerative effects in the intervertebral disc of L4-L5 and L5-S1 segments. This study aims to analyse the effects of disc degeneration and tears on the mechanical responses of the L5-S1 spinal unit, which has not been investigated. The annulus is represented by an anisotropic hyperelastic Gasser-Ogden-Holzapfel (GOH) model wherein the effect of degeneration is defined by varying the constants responsible for the behaviour of the material in different strain-ranges. A systematic approach is proposed for modelling the effects of disc degeneration in the annulus. Further, the commonly found anterior circumferential tear is modelled to understand its combined effects with degeneration of the annulus. The damaging effect of the tear was limited only to extension movement, causing critical stress variations in its vicinity. However, degeneration had a significant influence on both stress and range of motion of the spinal unit across all types of movements. This study highlights the complex relationship of the physiological movements with pathogenesis of tear and degeneration leading to discogenic pain thus enabling clinicians to develop conservative treatment strategies for specific age groups.

DOI： 10.1088/2057-1976/ad7608

Scopus

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生体軟組織の非線形な応力－ひずみ関係式と初期弾性率招待有り

山田　宏

機械の研究 ( 養賢堂 ) 76 ( 4 ) 247 - 257 2024年04月

Mechanical characterization of dissected and dilated human ascending aorta using Fung-type hyperelastic models with pre-identified initial tangent moduli for low-stress distensibility 査読有り国際誌

Bhat S.K., Yamada H.

Journal of the Mechanical Behavior of Biomedical Materials ( Elsevier BV ) 125 104959 2022年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Ascending aortic dissection (AD) is a potentially fatal vascular disease associated with degradation and fragmentation of the elastic fibers in the aortic media, increasing low-stress distensibility, and a dilated aorta may lead to dissection. In this study, a Fung-type hyperelastic model was formulated incorporating the initial tangent moduli (ITM) of stress–strain curves as an index of low-stress distensibility. ITM were correlated with the material constants by linearizing incompressible stress–strain relationships at zero strain. For uniaxial loading tests, the robustness of the material constants was examined in the stress ranges of 0–200, 0–180, and 0–160 kPa and to the ITM values of 100%, 95%, and 90%. Examination revealed stable changes in the material constants of 80% of the specimens. For equibiaxial stretch tests, the material constants were determined for each curve of the isotropic and anisotropic deformation groups by pre-identifying the ITM and minimizing fitting errors using isotropic or anisotropic models. The errors for all groups were <6% using a transversely isotropic model, and <10% for an orthotropic model. Comparisons with experimental curves showed that Fung-type models described both the ITM and significant stiffening at high stress levels. The mechanical characteristics of the aorta in the stage prior/posterior to dissection is such that while hardening occurs under both low- and high-stress levels with an increase in collagen content as an aging response, softening occurs under low-stress conditions due to histological abnormalities such as elastin deficiency and fragmentation. Numerical simulations using Fung-type models implied that elastic fiber degeneration and fragmentation in AD tissues reduced not only the low-stress stiffness but also the elastic stiffness with superimposed shear. The latter stiffness was modulated by the stiffening at high stress levels in tensile deformation behavior and normal-strain state under physiological loading conditions, and therefore provides further insight into wall rupture.

DOI： 10.1016/j.jmbbm.2021.104959

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褥瘡の発症・予防に関わる力学的因子の評価招待有り

山田宏

非破壊検査 70 ( 4 ) 158 - 164 2021年04月

Measurement and finite element analysis of the load-dependent pressure redistribution behavior of various types of mattresses 査読有り

Fuwa Y., Hasan W.Z.W., Yamada H.

Journal of Mechanics in Medicine and Biology 20 ( 5 ) 2020年06月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Load dependence must be kept in mind when evaluating mattress pressure redistribution, to prevent the development of pressure ulcers at bony prominences. However, there is no standardized method for analyzing load-dependent behavior after mattress pressure redistribution. In this study, a portable palmtop device with a simple load-sensing mechanism was developed for measuring the mean pressure exerted by a protruding shaft surrounded by a disc on low-resilience polyurethane (LRPu) foam, latex foam, coconut fiber and latex (CFL) mattresses, as well as polyurethane (Pu) foam bed and an LRPu foam mattress laid on a bed. Finite element (FE) analysis was used to analyze deformation and contact pressure in detail. The pressure redistribution was greatest for the LRPu foam mattress, and excessive compression was avoided by using an underlay made of stiff Pu foam. FE analysis revealed that the contact pressure increased significantly near the outer circumference of the protruding shaft and the surrounding disc. Significant nonuniformity in pressure was evident, according to the edge and bottom geometry of the device. The measurements and FE analysis revealed load-dependent pressure redistribution behavior, which should allow mattresses to be tailored on an individual basis.

DOI： 10.1142/S0219519420500311

Kyutacar

Scopus

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85091157593&origin=inward

Identification of uniaxial deformation behavior and its initial tangent modulus for atheromatous intima in the human carotid artery and thoracic aorta using three-parameter isotropic hyperelastic models 査読有り

Bhat S.K., Sakata N., Yamada H.

Journal of Mechanics in Medicine and Biology 20 ( 3 ) 2020年05月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 World Scientific Publishing Company. Uniaxial stretching tests are used for mechanical identification of small fibrous regions of atheromatous arteries. Material constants in isotropic hyperelastic models are determined to minimize the fitting error for the stress-strain curve. We developed a novel method to better characterize the material constants in typical forms of Yeoh, Ogden, Chuong-Fung (CF) and Gasser-Ogden-Holzapfel (GOH) isotropic hyperelastic models for fibrous caps and normal intimal layers from human carotid artery and thoracic aorta by incorporating Young's modulus, i.e., the initial tangent modulus of uniaxial stress-strain relationships, as one of three material constants. We derived a unified, isotropic form for the anisotropic exponential-Type strain energy density functions of CF and GOH models. The uniaxial stress-strain relationship equations were expanded to Maclaurin series to identify Young's modulus as a coefficient of the linear term of the strain and to examine the roles of the material constants in the nonlinear function. The remaining two material constants were determined by curvefitting. The incorporation of Young's modulus into the CF and GOH models gave reasonable curvefitting, with errors <10%, whereas large errors (>10%) were observed in one case for the Yeoh model and in two cases for the Ogden model.

DOI： 10.1142/S0219519420500141

Kyutacar

Scopus

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85084917787&origin=inward

High Salt intake worsens aortic dissection in mice: Involvement of IL (Interleukin)-17A-dependent ECM (extracellular matrix) metabolism 査読有り

N. Nishida, H. Aoki, S. Ohno-Urabe, M. Nishihara, A. Furusho, S. Hirakata, M. Hayashi, S. Ito, H. Yamada, Y. Hirata, H. Yasukawa, T. Imaizumi, H. Tanaka, Y. Fukumoto

Arteriosclerosis, Thrombosis, and Vascular Biology 40 ( 1 ) 189 - 205 2020年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

OBJECTIVE: Aortic dissection (AD) is a fatal disease that occurs suddenly without preceding clinical signs or symptoms. Although high salt intake is a proposed risk factor for cardiovascular diseases, the relationship between AD and high salt intake has not been clarified. We examined the effect of high-salt challenge on a mouse AD model. Approach and Results: AD was induced in male mice by continuous infusion of β-aminopropionitrile and Ang II (angiotensin II). High-salt challenge exacerbated aortic wall destruction in AD. Deletion of Il17a (IL-17KO [IL (interleukin)-17A knockout]) did not affect the AD phenotype at baseline, but it abolished the high salt-induced worsening of the aortic destruction. Unexpectedly, aortas of IL-17KO mice exhibited global changes in ECM (extracellular matrix)-related genes without alteration of proinflammatory genes, altered architecture of collagen fibers, and reduced stiffness before AD induction. The aortas of IL-17KO mice were less sensitive to AD-inducing stimuli, as shown by the induction of phenotypic modulation markers SMemb and vimentin, suggesting a reduced stress response. The aortas of IL-17KO mice had a higher population of smooth muscle cells with nuclear-localized phosphorylated Smad2, indicative of TGFβ (transforming growth factor-beta) signal activation. Consistently, pretreatment of smooth muscle cells in culture with IL-17A blunted the activation of Smad2 by TGFβ1. CONCLUSIONS: These findings indicate that high salt intake has a worsening effect on AD in the context of high aortic wall stiffness, which is under the control of IL-17A through ECM metabolism. Therefore, salt restriction may represent a low-cost and practical way to reduce AD risk.

DOI： 10.1161/ATVBAHA.119.313336

Scopus

PubMed

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85077221754&origin=inward

Finite element modelling of a bulging behavior in a cerebral artery with dissection 査読有り国際誌

S. K. Bhat, H. Yamada, N. Sakata

CMBE19 Proceedings, 6th International Conference on Computational & Mathematical Biomedical Engineering 838 - 841 2019年06月

Application of finite element analysis on balloon expandable coronary stents: A review

Bekal C., Yamada H., Shetty R., Shenoy S.

International Journal of Engineering and Technology(UAE) ( Science Publishing Corporation Inc ) 7 ( 3 ) 1640 - 1647 2018年08月

記述言語：英語掲載種別：記事・総説・解説・論説等（学術雑誌）

© 2018 Chandrakantha Bekal et. al. Numerical analysis of complex physical environment continues to be preferred over "build and test" approach in product development process. Finite Element Analysis (FEA) of coronary artery stenting is studied and researched worldwide for many years. Potential of using FEA for mimicking in-vivo is high as experimental test is ruled out for variety of reasons. This review aims at discussing issues and challenges of numerical simulation based on part of available literature on usage of FEA techniques for investigating behavior of balloon expandable (BE) coronary stents inside artery. Literatures of past 16 years of study on the structural analysis is summarized and potential issues for research is discussed. Study tries to investigate deployment characteristics and biomechanical response of artery post stenting and significance of non-physiological conditions induced. Effects of geometrical parameters, simulation strategies are summarized. Study mainly underscores the potential challenges of reliable numerical investigation. Scope of FEA in predicting contributor for in-stent reste-nosis (ISR), a major drawback of stenting procedure, by correlating the engineering aspect of stent design and its clinical significance supported by clinical trials are highlighted. Study is expected to serve as qualitative assessment for cardiologists to minimize procedural failure and quantitative tool for the designers for stent optimization.

DOI： 10.14419/ijet.v7i3.13845

Scopus

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Finite element analysis of a rupture-induced deformation of a carotid atherosclerotic plaque with intraplaque hemorrhage 査読有り

ESMAEILI MONIR Hamed, SENJU Omi, OGATA Toshiyasu, INOUE Tooru, SAKATA Noriyuki, YAMADA Hiroshi

Journal of Biomechanical Science and Engineering 13 ( 1 ) 17-00436 2018年03月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

<p>Intraplaque hemorrhage (IPH), bleeding in a plaque, is caused by a neocapillary rupture in an atherosclerotic plaque. We used contrast-enhanced ultrasonography to diagnose carotid atherosclerotic plaques before carotid endarterectomy (CEA), a surgical operation to remove an arterial intimal layer including a plaque lesion. We found lumenward (inward) deformation in some cases of ruptured plaques with IPH. The aim of this study was to evaluate the mechanical effects of infiltrated blood in the lipid core on the luminal shape of the ruptured plaque in the short-axis view. We created a finite element model of a carotid artery bifurcation with a ruptured plaque based on a sample obtained from CEA. As physiological loads, we assigned pressures on the surfaces of the lumen and the lipid core, the sum of a gradual pressure drop in the artery obtained from computational fluid dynamics analysis and a uniform pressure, and a constant longitudinal stretch. In the simulation, the fibrous cap in the ruptured model became almost flat in the short-axis view with lumenward deformation, being less deformed than that observed in ultrasonography. The simulation results show that inward deformation of the fibrous cap is correlated with an equal pressure in the lumen and the lipid core. In comparison, a hyperelastic model of soft unruptured plaque reproduced a round lumen. A better understanding of contrast-enhanced ultrasonography images from a mechanical perspective may facilitate the morphological identification of plaque rupture with IPH.</p>

DOI： 10.1299/jbse.17-00436

Scopus

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130006247203

Skin stiffness determined from occlusion of a horizontally running microvessel in response to skin surface pressure: a finite element study of sacral pressure ulcers 査読有り

H. Yamada, Y. Inoue, Y. Shimokawa, K. Sakata

Medical & Biological Engineering & Computing 55 ( 1 ) 79 - 88 2017年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Pressure ulcers occur following sustained occlusion of microvessels at bony prominences under skin surface pressure (SSP). However, the mechanical conditions of the surrounding soft tissue leading to microvascular occlusion are not fully understood. This study determined the stiffness of homogenized skin with microvasculature at the sacrum that occludes microvessels at an SSP of 10 kPa (consistent with a standard mattress) and recovers from occlusion at 5 kPa (consistent with a pressure-redistribution mattress). We conducted two-dimensional finite element analyses under plane stress and plane strain conditions to determine the stiffness of the skin. The results for plane stress conditions show that the microvessel was occluded with a Young’s modulus of 23 kPa in response to an SSP of 10 kPa at the center of the sacrum and that the circulation recovered following a reduction in the SSP to 5 kPa. The resulting Young’s modulus is consistent with reported data. Our study indicates that the critical value of the SSP for microvascular occlusion is determined not only by the stiffness of homogenized skin with microvasculature but also by the intraluminal pressure, microvascular wall stiffness, and body support conditions.

DOI： 10.1007/s11517-016-1500-2

Scopus

PubMed

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84964301412&origin=inward

Assessment of the relationship between deformation characteristics and the presence of calcification in human atheromatous plaques using uniaxial stretching evaluations with digital image correlation, CT scanning and histological examination 査読有り

H. Esmaeili Monir, H. Yamada, N. Sakata, Y. Morita, Y. Nakashima

Journal of Biomechanical Science and Engineering 11 ( 3 ) 15-00611 2016年09月

Finite element modelling of the common carotid artery in the elderly with physiological intimal thickening using layer-specific stress-released geometries and nonlinear elastic properties 査読有り国際誌

H. Esmaeili Monir, H. Yamada, N. Sakata

Computer Methods in Biomechanics and Biomedical Engineering 19 ( 12 ) 1286 - 1296 2016年09月

力学試験と超弾性モデルの適用によるウレタンフォームマットレスの骨突起部圧分散メカニズムの解明査読有り

井上仁瑛，山田宏

バイオメカニズム 23 233 - 242 2016年07月

Age-related distensibility and histology of the ascending aorta in elderly patients with acute aortic dissection 査読有り

H. Yamada,N. Sakata,H. Wada,T. Tashiro,E. Tayama

Journal of Biomechanics 48 ( 12 ) 3267 - 3273 2015年09月

A nonlinear finite element simulation of balloon expandable stent for assessment of plaque vulnerability inside a stenotic artery（共著）査読有り

A. Karimi, M. Navidbakhsh, H. Yamada, R. Razaghi

Medical & Biological Engineering & Computing 52 ( 7 ) 589 - 599 2014年07月

Reconstruction of small diameter arteries using decellularized vascular scaffolds（共著）査読有り

Y. Nagaoka, H. Yamada, T. Kimura, A. Kishida, T. Fujisato, K. Takakuda

Journal of Medical and Dental Sciences 61 ( 1 ) 33 - 40 2014年03月

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