Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Dental Materials and Devices  

DOI： 10.4012/dmj.2022-136

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: Suprahyoid muscles behavior during the tongue lifting movement has not yet been elucidated. OBJECTIVE: The purpose of this study was to investigate the potential of elastography imaging to examine developmental oral dysfunction in children and oral hypofunction in older adults using sonography. METHODS: Tongue pressure was measured using a manometer with a probe. The tongue pressure was measured with simultaneously scanning the geniohyoid muscle (GHM) and the anterior belly of the digastric muscle (DGM) using sonographic elastography. Sagittal images of the GHM and coronal images of the DGM were used for the strain ratio measurement. The strain ratio of the muscles was measured three times for each subject with the tongue pressure values of 0-30 kPa. RESULTS: The strain ratio of the GHM were higher than those of the DGM at tongue pressure of 10, 20 and 30 kPa. The strain ratio of the GHM increased as the tongue pressure increased in all participants. In contrast, the strain ratio of the DGM tended to slowly decrease as tongue pressure increased in female participants. CONCLUSION: Sonographic elastography is useful for visual and quantitative evaluation of elastic properties in suprahyoid muscles during tongue lifting movements.

DOI： 10.3233/BME-221414

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Authorship：Corresponding author   Language：Japanese  

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Authorship：Corresponding author   Language：Japanese   Publisher：(一社)日本臨床バイオメカニクス学会  

正常咬合者13名の上下顎骨を撮影したコーンビームCT画像の三次元骨モデルの3点の特徴点から口腔内に三次元ワールド座標系を設定し,横断面,冠状面および矢状面を定めた.そして,歯形状より主成分分析法によって三次元歯軸を求めた.歯軸を3平面上に投影して,各平面内での上下顎全歯の対向する同名歯種の歯軸のなす角度である交角度を求めた.さらに,異なる歯種間の交角度の関係について示した.その結果,投影した平均交角度は3平面内においていずれも正中面に対してほぼ左右対称の傾向を示した.横断面および矢状面内の交角度は前歯では小さく,第二小臼歯,第一大臼歯,第二大臼歯では,他歯種と比べて交角度は大きい.一方,異なる歯種間の交角度の相関は,横断面内の中切歯,側切歯,犬歯では隣接する歯種間に有意な正の相関が認められた.矢状面内では,第二大臼歯以外は多くの歯種間で交角度の相関がみられることを明らかにした.(著者抄録)

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: Knowledge of the biomechanics of the normal collateral ligaments is important to secure optimal stability of the knee following injury. Various in vitro methods have been described in evaluating the biomechanics of these ligaments. However, a method of direct evaluation has not been reported. OBJECTIVE: To determine the stiffness characteristics of the collateral ligaments of the knee using strain ultrasound elastography. METHODS: Strain ultrasound elastography was performed on different components of the collateral ligaments in various angles of knee flexion in 18 healthy males (36 ligaments). We measured relative stiffness of the ligaments using strain ratio (SR = target tissue strain/reference strain). A lower strain ratio indicates higher relative stiffness. RESULTS: There was moderate to excellent intra- and inter-rater agreement for strain ratio measurements in all ligament portions. Strain ratios were lowest at 0° in all three ligaments, indicating high relative stiffness. In the superficial and deep medial collateral ligaments, the strain ratio increased with increasing knee flexion, whereas in the lateral collateral ligament, stiffness showed a tendency to fluctuate. CONCLUSION: Strain ultrasound elastography is a reliable tool for monitoring relative stiffness of the collateral ligaments of the knee and is easily applied to the routine clinical setting.

DOI： 10.3233/BME-211282

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Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/mej.21-00400

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Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Dental Materials and Devices  

DOI： 10.4012/dmj.2021-146

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

大規模集団検診(松代膝検診)で確認した変形性膝関節症(膝OA)進行に伴う膝前後単純X線画像上の下腿骨位置や形状の定量的評価で膝OA進行度判定が可能と考え、半自動評価システムを開発した。松代膝検診第5回(2007年)から12年間の5回をすべて受診した対象のうち、任意で抽出した男女各10名の単純X線画像を対象に測定の信頼性を評価および従来の手動デジタイズ法との測定精度と測定時間を比較検討した。測定の信頼性として検者内では級内相関係数:ICC=0.98、検者間ではICC=0.96、従来法との比較でもICC=0.96と高い信頼性を示した。また、評価指標で、脛骨関節面傾斜、関節裂隙幅比の減少、脛骨内側皮質骨幅比の増加、FTAの増加など過去に報告した膝OA進行に伴う変化が算出された。特に、骨の参照軸の自動抽出により測定値の安定とこれによる測定時間が約1/3に短縮した。(著者抄録)

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Authorship：Corresponding author   Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

本研究では、成人10名の上下顎骨を撮影したコーンビームCT画像から骨モデルを三次元再構成し、解剖学的特徴箇所である下顎両側オトガイ孔2点および上顎切歯管1点を利用して口腔内に三次元ワールド座標系を構築し、全ての歯の三次元モデルを作成した。各歯の幾何学的重心(COG)と主成分分析法で計算した歯軸(PC-A)を求め、空間内のCOGとPC-Aを横断面、冠状面および矢状面上に投影して、各平面内でのPC-A角度とCOGによる歯列を示した。その結果、冠状面では、上顎歯は全て頬側に歯が傾き、下顎歯は、中切歯、側切歯、犬歯、第一小臼歯は頬側に向いているが、第二小臼歯、第一、第二大臼歯は舌側を向く。矢状面では、上顎歯は第二大臼歯だけが遠心側に傾いているのに対し、下顎歯は全て近心側に傾くという一般的な正常咬合者の特徴を定量的に明らかにした。さらに、3平面内におけるCOG位置とPC-A角度との関係を表す回帰曲線は、簡潔な多項式で表現できることを示した。(著者抄録)

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Other Link： https://search-tp.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2021&ichushi_jid=J05471&link_issn=&doc_id=20211007090014&doc_link_id=%2Fcx9biomc%2F2021%2F004200%2F015%2F0079-0085%26dl%3D0&url=https%3A%2F%2Fwww.medicalonline.jp%2Fjamas.php%3FGoodsID%3D%2Fcx9biomc%2F2021%2F004200%2F015%2F0079-0085%26dl%3D0&type=MedicalOnline&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00004_2.gif

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOS Press  

BACKGROUND: The patellar and quadriceps tendons are responsible for the extension mechanism of the knee joint and frequently become inflamed during sports. Diagnosis and determination of when an athlete can return to sports following these injuries are usually performed by assessing morphological features and functional outcomes. Nevertheless, mechanical properties are not being assessed. OBJECTIVE: To describe the stiffness characteristics of these two tendons over the range of knee flexion and to test the feasibility of using strain ultrasound elastography (SE). METHODS: SE with an acoustic coupler as the reference was performed for nine healthy males. Relative stiffness measurements were obtained using the strain ratio (SR = target tissue strain/reference strain) by placing the knee in five different flexion angles. Lower SR indicates higher relative stiffness. RESULTS: This study showed reliable measurement with good intra- and inter-rater agreement for SR at 30°. SR of the quadriceps tendon decreases as knee flexion increases, indicating increased relative stiffness. In the patellar tendon, no significant difference was observed between 30° and 60°. Beyond 60°, relative stiffness increased constantly. CONCLUSIONS: SE is a reproducible and feasible tool to monitor relative stiffness of the patellar and quadriceps tendons in routine clinical settings.

DOI： 10.3233/bme-206016

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Indentation tests have been widely used to evaluate the mechanical properties of industrial and biological materials in many studies. In this study, we obtained an analytical solution for the axisymmetric contact problem for a viscoelastic layer bonded to a rigid substrate and indented by a flat‐ended cylindrical punch using the elastic–viscoelastic correspondence principle. The analytical solution was obtained from a method using an infinite system of simultaneous equations instead of a conventional method using the second kind of Fredholm equation. Relaxation indentation tests were conducted for silicon rubber, polyurethane gel (a soft material used for elastography), and articular cartilage from a bovine femoral head. The articular cartilage was tested as obtained and then tested again after treatment by collagenase. The viscoelastic models in this study were a three‐element model (standard linear solid model) and a five‐element model (generalized Maxwell model), and the viscoelastic parameters for the models were determined by fitting the analytical solution to results for applied load as it varied over time during relaxation indentation tests. The results suggested that the five‐element model was more appropriate than the three‐element model for reproducing the relaxation indentation behavior of silicon rubber, polyurethane gel, and articular cartilage. Furthermore, the viscoelastic parameters for treated articular cartilage clearly decreased compared with those for unaltered articular cartilage. These results suggest that the method for evaluating the time‐dependent mechanical properties of articular cartilage based on analytical solutions of relaxation indentation tests could be a useful tool for evaluating the state of degenerated cartilage.

DOI： 10.1002/zamm.202000272

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/zamm.202000272

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

BACKGROUND: Proper identification of lumbosacral transitional vertebrae (LSTV) is important to characterize the relationship between the transitional segment and adjacent levels. Classical classification schemes are inaccurate with respect to the whole spine. We propose a precise vertebral numbering method and investigated the relationship between LSTV and whole-body sagittal alignment. METHODS: A total of 291 healthy adult volunteers with no history of spinal disease were evaluated with biplanar slot scanning full body stereoradiography to determine the prevalence of LSTV. Vertebrae were counted from the first cervical vertebra using both coronal and sagittal plane images. We then investigated the influence of LSTV on whole-body sagittal alignment in 279 participants. Whole-body key parameters descriptive statistics were compared among groups according to the number of vertebrae (L4, L5, and L6). Statistical analysis was performed between normal and LSTV cases using the Steel-Dwass analysis. RESULTS: Of the 291 subjects, 14 (4.8%) had 23 vertebrae and 16 (5.5%) had 25 vertebrae. Eleven (3.8%) had Th11, 3 (1.0%) had L4, and 1 (0.3%) had Th11 + L6, 16 (5.5%) had L6. Compared with the normal group, the sacral base in relation to the pelvis was higher in the L4 group and lower in the L6 group. The C2-C7 angle and lumbar lordosis (LL) were increased in both the L4 and L6 groups. All remaining parameters were decreased in the L4 group and increased in the L6 group. The relationship between LL and PI was similar in the normal and LSTV groups, despite the difference in the sacral base location. CONCLUSIONS: We propose a precise method for numbering the vertebrae using coronal and sagittal full body images. The spinopelvic parameters of the LSTV population significantly differed from those in the normal spine population due to differences in the sacral base location.

DOI： 10.1016/j.jos.2021.03.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

<p>The axisymmetric problem of a multi-layer composite with a penny-shaped crack, which is parallel to the interface between elastic layers, in the center plane is considered. It is assumed that each elastic layer, which has a unique elastic constant, is perfectly bonded to its adjacent elastic layers. The multi-layer composite is subjected to uniform internal pressure on the crack surface. The dual integral equations obtained for the problem are reduced to an infinite system of simultaneous equations by expressing the normal displacements on the crack surface as an appropriate series function. The boundary conditions between adjacent elastic layers can be generally formulated using the transfer matrix method. Numerical results were obtained in hard- and soft-layer composite systems, for which the elastic properties of each layer linearly increase and decrease towards the crack plane, respectively. This study shows not only the results of the mode I stress intensity factor at the crack tip, but also the distribution of normal stress and displacement at the crack plane. Furthermore, sandwich structures composed of three materials with different mechanical properties were considered. Numerical calculations show several conclusions that a stiffer layer should be placed father away from the crack surface to decease the stress intensity factor and the hardness of the middle layer contributes to the stress intensity factor for the sandwich structures.</p>

DOI： 10.1299/mej.21-00025

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The sequential oral functions of mastication and swallowing are well tuned in humans. To prevent oral hypofunction as a risk factor for systemic frailty by oral motor training, semi-powered exoskeleton was developed and evaluated its loading/assist effects by monitoring electromyography signals and saliva secretion in healthy persons. The actuator of the driving unit combined mechanical and powered mechanics and was driven alternatively by an unpowered stainless-steel spring system for jaw-opening training by loading and a powered shape-memory alloy spring system to assist jaw closing. Sequential device movement was controlled by two electronic circuits with two magnetic switching systems to match human jaw movement. This exoskeleton realized a 25% increase of jaw-opening muscular activity for training, 15% saving of jaw-closing muscular activity for assistance, and 15% enhancement of saliva secretion, which could contribute to the prevention of oral frailty by maintenance and strengthening of oral function in the upcoming super-aging society.

DOI： 10.4012/dmj.2019-400

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BACKGROUND: Identifying the time course of rotational knee alignment is crucial for elucidating the etiology in knee osteoarthritis. OBJECTIVE: The aim of this study was to propose new rotational indices for calculating the change in relative rotational angles between the femur and tibia in standing anteroposterior (AP) radiographs. METHODS: Forty healthy elderly volunteers (20 women and 20 men; mean age, 70 ± 6 years) were assessed. The evaluation parameters were as follows: (1) femoral rotational index: the distance between the sphere center of the medial posterior femoral condyle and the lateral edge of the patella, and (2) tibial rotational index: the distance between the medial eminence of the tibia and the lateral edge of the fibula head. The indices were standardized by the diameter of the sphere of the medial posterior femoral condyle. This study (1) identified the relationship between changes in rotational indices and the simulated rotational knee angles in the standing position, (2) proposed a regression equation for the change in relative rotational angles between the femur and tibia in standing AP radiographs, and (3) verified the accuracy of the regression equation. RESULTS: The rotational indices increased in direct proportion to simulated rotational knee angles (femoral index: r > 0.9,p < 0.0001; tibial index: r > 0.9, p < 0.0001). Based on the results, the regression equation with the accuracy of 0.45 ± 0.26° was determined. CONCLUSIONS: The proposed regression equations can potentially predict the change in relative rotational angles between the femur and tibia in a pair of standing AP radiographs taken at different dates in longitudinal studies.

DOI： 10.3233/BME-201138

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BACKGROUND: Lip closing functions have never been evaluated from the viewpoint of elastic properties. OBJECTIVES: The purpose of the present study was to investigate the behavior of the lower orbicularis oris muscle during a button-pull exercise to measure lip closing force and quantitatively evaluate its elastic properties using sonographic elastography. METHODS: Appropriate compression loads for elastography were randomly measured on one of three types of acoustic couplers on three examiners. Compression tests were performed on three types of acoustic couplers within the appropriate compression load. Using the acoustic coupler with the lowest elastic modulus, the strain ratio of the lower orbicularis oris muscle during lip closing was measured, and elastography was performed on six males under tension loads of 0-8 N. RESULTS: The intraclass correlation coefficient (1, 3) for the tension load of 0 N was 0.81. Elastography showed that the strain ratio values increased significantly (p < 0.05) as the tension load increased. CONCLUSIONS: Combining the data obtained from lip closing test devices and sonographic elastography enabled the muscle performance to be evaluated objectively and accurately.

DOI： 10.3233/BME-201101

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PURPOSE: This study aimed to evaluate the age- and sex-related characteristics in cortical thickness of the tibial diaphysis between non-obese healthy young and elderly subjects as reference data. METHODS: The study investigated 31 young subjects (12 men and 19 women; mean age, 25 ± 8 years) and 54 elderly subjects (29 men and 25 women; mean age, 70 ± 6 years). Three-dimensional estimated cortical thickness of the tibial diaphysis was automatically calculated for 5000-9000 measurement points using the high-resolution cortical thickness measurement from clinical computed tomography data. In 12 assessment regions created by combining three heights (proximal, central, and distal diaphysis) and four areas of the axial plane at 90° (medial, anterior, lateral, and posterior areas) in the tibial coordinate system, the standardized thickness was assessed using the tibial length. RESULTS: As structural characteristics, there were no differences in the medial and lateral thicknesses, while the anterior thickness was greater than the posterior thickness in all groups. The sex-related difference was not shown. As an age-related difference, elderly subjects showed greater or lesser cortical thickness than the young subjects, depending on the regions of the tibia. CONCLUSIONS: Cortical thickness was different depending on sex, age, and regions in the tibia. The results of this study are of clinical relevance as reference points to clarify the causes of various pathological conditions for diseases. LEVEL OF EVIDENCE: Level 3.

DOI： 10.1186/s40634-020-00297-9

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer  

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INTRODUCTION: Cortical thickness of the femoral diaphysis is assumed to be a preferred parameter in the assessment of the structural adaptation by mechanical use and biological factors. This study aimed to investigate the age- and sex-specific characteristics in cortical thickness of the femoral diaphysis between young and elderly non-obese people. MATERIALS AND METHODS: This study investigated 34 young subjects (21 men and 13 women; mean age: 27 ± 8 years) and 52 elderly subjects (29 men and 23 women; mean age: 70 ± 6 years). Three-dimensional (3D) cortical thickness of the femoral diaphysis was automatically calculated for 5000-8000 measurement points using the high-resolution cortical thickness measurement from clinical CT data. In 12 assessment regions created by combining three heights (proximal, central, and distal diaphysis) and four areas of the axial plane at 90° (medial, anterior, lateral, and posterior areas) in the femoral coordinate system, the standardized thickness was assessed using the femoral length. RESULTS: As per the trends, (1) there were no differences in medial and lateral thicknesses, while the posterior thickness was greater than the anterior thickness, (2) the thickness in men was higher than that in women, and (3) the thickness in young subjects was higher than that in elderly subjects. CONCLUSIONS: The results of this study are of clinical relevance as reference points to clarify the causes of various pathological conditions for diseases of the lower extremities.

DOI： 10.1007/s00774-019-01079-9

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s12565-019-00506-1

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Other Link： http://link.springer.com/article/10.1007/s12565-019-00506-1/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/jbse.19-00616

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

<p> Trapeziometacarpal joint (TMC joint) of thumb is one of the joints having a complicated shape which enables to generate a wide variation of finger movements in daily life. It is important to clarify the accurate in vivo contact behavior of healthy TMC joint when evaluating post-operative joint movements. Thus, author analyzed TMC joint contact behavior in 4 different finger positions of 8 healthy adult males using magnetic resonance imaging (MRI) system. From MR images, three-dimensional bone models were constructed and a three-dimensional coordinate system was defined by the characteristic shape of each bone model. Then, three bone axial angles and three-dimensional bone motion of each 4 positions in the TMC joint were calculated: abduction-adduction, extension-flexion, pronation-supination, and Euler angles. Furthermore, contact areas of the articular cartilage in each of 4 positions were clarified from MR images. Results have shown that, the contact area changed with changing of the thumb position and it was maximum oat the thumb extension. In addition, it was clarified that the contact area moved according to the thumb position.</p>

DOI： 10.11395/jjsem.20.39

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J-GLOBAL

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Authorship：Corresponding author   Language：Japanese  

J-GLOBAL

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J-GLOBAL

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00586-019-06118-7

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Other Link： http://link.springer.com/article/10.1007/s00586-019-06118-7/fulltext.html

Authorship：Corresponding author   Language：English  

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Authorship：Corresponding author   Language：English  

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Language：Japanese   Publisher：(公社)日本放射線技術学会  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: In vivo evaluation of the elastic properties of the knee joint capsule has not been adequately performed. OBJECTIVES: To establish a methodology to assess the stiffness of the normal knee joint capsule over a range of knee flexion angles using ultrasound elastography. METHODS: Ultrasound elastography with an acoustic coupler was used to assess the stiffness of the anteromedial capsule of the knee joints of 10 male (mean age 22.63 ± 1.02 years) and 10 female (mean age 21.6 ± 0.8 years) subjects at static knee flexion angles of 0°, 45°, 90°, and 120°. Relative stiffness of the capsule was obtained using the strain ratio (SR), defined as the ratio of the strain in the capsule to that in the acoustic coupler. RESULTS: The intraclass correlation coefficient (1, 3) ranged from 0.95 to 0.96, and the correlation coefficient between examiners (2, 3) was 0.94. SR values decreased significantly as the flexion angle increased (P < 0.01). At 90° and 120°, it was significantly higher in female than in male subjects (P < 0.01). CONCLUSIONS: This study established a feasible and reproducible method to obtain the stiffness characteristics of the anteromedial knee joint capsule using ultrasound elastography with an acoustic coupler.

DOI： 10.3233/BME-191046

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemecj.2019.J02513

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmeatem.2019.1010B1100

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J-GLOBAL

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J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：National Committee for IUTAM  

We focus on an elastic contact problem for indentation of a layer-substrate body. An elastic layer assumed to be perfectly bonded to an elastic semi-infinite substrate. The elastic layer is smoothly indented with a flat-ended cylindrical indenter and a spherical indenter. The analytical and exact solutions are obtained by solving an infinite system of simultaneous equations using the method to express a normal contact stress at the upper surface of the elastic layer as an appropriate series. This paper presents not only the axial load but also the distribution of the dimensionless normal contact stress under cylindrical and spherical indentation, the distribution of the dimensionless normal displacement at the upper surface of the elastic layer and the stress singularity factor. Numerical results are given for several combinations of the ratio of shear modulus and Poisson&rsquo;s ratios of the elastic layer and substrate, and the thickness of the elastic layer.

DOI： 10.11345/nctam.64.81

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Authorship：Lead author,　Corresponding author   Language：Japanese  

J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：国立大学入学者選抜研究連絡協議会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Tokyo  

Objectives: The present study was performed to investigate the mineral density distribution in enamel and dentin for both permanent and primary teeth and to establish the standard density per tooth type using micro-computed tomography (CT). Methods: Fifty-seven extracted human teeth (37 permanent, 20 primary) were evaluated in the present study. The enamel and dentin mineral densities in the extracted teeth were measured using micro-CT. Cubic regression curves were used to determine the mineral density distribution in the enamel and dentin for each tooth type. Results: The mean values, distributions, and regression equations of the mineral densities were obtained. The mean mineral density values for permanent enamel and dentin were significantly higher than those for their primary counterparts for each tooth type. Conclusions: In the present study, we demonstrated the distribution of mineral density in sound enamel and dentin and attempted to determine the standard mineral density for each tooth type using micro-CT. The mineral density distributions found in this study contribute to our understanding of the mechanical properties of enamel and dentin. A positive correlation suggests that the systemic bone mineral density could be predicted based on the analysis of exfoliated teeth, such as in patients with hypophosphatasia. The present results may be useful in establishing a numerical standard for the mechanism involved in root fracture and for early detection of root fracture risk.

DOI： 10.1007/s11282-018-0315-2

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

<p>Herein, we consider the axisymmetric problem of a penny-shaped crack in an elastic material sandwiched between other materials. It is assumed that the central substance is composed of an elastic layer held between two semi-infinite bodies with different elastic constants, and that the crack is situated in the central plane of the elastic layer and subjected to uniform pressures on its internal surfaces. We consider two contact conditions; perfectly bonded and frictionless contact at the interfaces with the dissimilar materials. Dual integral equations are reduced to an infinite system of simultaneous equations by expressing normal displacements on the crack surfaces as an appropriate series function. Numerical results were obtained to examine the effects of the elastic constants of the layer and semi-infinite bodies and contact conditions on the stress intensity factor at the tip of the penny-shaped crack, the distribution of normal displacement, and stress on the crack plane. Based on the results of these numerical calculations, several conclusions can be made, as follows. 1) The distributions of normal displacement and stress at the crack plane and the stress intensity factor at the tip of the crack become larger than the results for an infinite solid when the ratio of the shear modulus of the layer to that of the semi-infinite bodies is larger than 1. 2) The numerical results for normal displacement and stress, and for stress intensity factors, in the frictionless case are higher than for the perfectly bonded case regardless of the shear modulus ratio and layer thickness ratio. The difference between the perfectly bonded and frictionless cases becomes greater as the layer thickness ratio becomes smaller. 3) There is a slight difference in the stress intensity factor values obtained from the present work and the corresponding results previously reported in the literature.</p>

DOI： 10.1299/mej.18-00125

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<p>Herein, we consider the axisymmetric problem of a penny-shaped crack in an elastic material sandwiched between other materials. It is assumed that the central substance is composed of an elastic layer held between two semi-infinite bodies with different elastic constants, and that the crack is situated in the central plane of the elastic layer and subjected to uniform pressures on its internal surfaces. Dual integral equations are reduced to an infinite system of simultaneous equations by expressing normal displacements on the crack surfaces as an appropriate series function. Numerical results were obtained to examine the effects of the elastic constants of the layer and semi-infinite bodies on the stress intensity factor at the tip of the penny-shaped crack, the distribution of normal displacement, and stress on the crack plane. As a result, there is a slight difference in the stress intensity factor values obtained from the present work and the corresponding results previously reported in the literature.</p>

DOI： 10.1299/jsmemecj.2018.G0300401

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<p>We considered the axisymmetric contact problem of multi-elastic layer with different elastic constants bonded on elastic semi-infinite substrate indented by a rigid flat-ended cylindrical indenter. In this study, the information of each elastic layers can be sorted by using transfer matrix method and dual integral equations were reduced to an infinite system of simultaneous equations by expressing a normal contact stress at the surface elastic layer as an appropriate series. Numerical results were obtained to demonstrate the effects of the elastic constants of each elastic layers and semi-infinite elastic substrate on the radial distribution of normal contact stress and normal displacement of free surface of elastic layer, stress singularity factor at the edge of cylindrical indenter, and applied load of rigid indenter which needed to penetrate to a constant depth into multi-layered materials. The present results of applied load were good agreement with the results of the previous other studies. Numerical results were given for several combinations of the shear modulus of each elastic layers and substrate, and Poisson's ratio of both each elastic layers and substrate was fixed as 0.3 throughout present study. These results give us great contribution to the establishment of the indentation tests on composite materials as well as the guideline for design of appropriate mechanical properties of layered materials.</p>

DOI： 10.1299/jsmemm.2018.GS0504

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<p>The indentation test has been widely used to evaluate mechanical properties of industrial and biological materials in many studies. In this study, we obtained an analytical solution of axisymmetric contact problem of viscoelastic layer bonded on rigid substrate indented by flat-ended cylindrical punch using elastic-viscoelastic corresponding principle. The relaxation indentation tests were conducted for silicon rubber, Echo PAD which is a soft material used for elastography, and articular cartilage of bovine femoral head. For articular cartilage, fresh articular cartilage was treated by collagenase after a relaxation indentation test and was then used again in same test. The viscoelastic models in this study were selected as three-element model (standard linear solid model) and five-element model (generalized Maxwell model) and viscoelastic parameters of the models were determined by fitting the analytical solution to applied load varying with time collected from the relaxation indentation test. As the results, it was suggested that the five-element model was more appropriate than three-element model to reproduce the behavior of relaxation indentation of silicon rubber, Echo PAD, and articular cartilage. Furthermore, the viscoelastic parameters of treated articular cartilage decreased sufficiently compared with those of fresh articular cartilage. From these results, it was suggested that the method of evaluating the time-dependent mechanical properties of articular cartilage based on the analytical solutions of the relaxation indentation test obtained from this study could be a useful tool for evaluating the state of degenerated cartilage.</p>

DOI： 10.1299/jsmemm.2018.OS0604

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

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Introduction: The relative torsional angle of the distal tibia is dependent on a deformity of the proximal tibia, and it is a commonly used torsional parameter to describe deformities of the tibia; however, this parameter cannot show the location and direction of the torsional deformity in the entire tibia. This study aimed to identify the detailed deformity in the entire tibia via a coordinate system based on the diaphysis of the tibia by comparing varus osteoarthritic knees to healthy knees.
Methods: In total, 61 limbs in 58 healthy subjects (age: 54 18 years) and 55 limbs in 50 varus osteoarthritis (OA) subjects (age: 72 7 years) were evaluated. The original coordinate system based on anatomic points only from the tibial diaphysis was established. The evaluation parameters were 1) the relative torsion in the distal tibia to the proximal tibia, 2) the proximal tibial torsion relative to the tibial diaphysis, and 3) the distal tibial torsion relative to the tibial diaphysis.
Results: The relative torsion in the distal tibia to the proximal tibia showed external torsion in both groups, while the external torsion was lower in the OA group than in the healthy group (p &lt; 0.0001). The proximal tibial torsion relative to the tibial diaphysis had a higher external torsion in the OA group (p = 0.012), and the distal tibial torsion relative to the tibial diaphysis had a higher internal torsion in the OA group (p = 0.004) in comparison to the healthy group.
Conclusion: The reverse torsional deformity, showing a higher external torsion in the proximal tibia and a higher internal torsion in the distal tibia, occurred independently in the OA group in comparison to the healthy group. Clinically, this finding may prove to be a pathogenic factor in varus osteoarthritic knees. Level of evidence: Level Ill. (C) 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jos.2017.01.002

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The action of the forearm is to transfer force and torque across the elbow and wrist, resulting in axial rotation at the distal and proximal radioulnar joints, called pronation and supination. Pronation and supination are important functions as they allow many kinds of activities of daily living. Three-dimensional (3D) motion analysis of pronation and supination is essential for a better understating of the biomechanics of the forearm to describe the physiological range of motion and optimize clinical options for disorders of the forearm. Although numerous in vitro studies have contributed to gain insights into the forearm pronation and supination, in vivo investigations are still limited. In this study, three-dimensional (3D) motion of the distal radioulnar joint (DRUJ) during forearm pronation and supination was analyzed in vivo using biplanar radiography and 3D models of the ulna and radius. Twelve healthy subjects (6 men and 6 women) were recruited for the study. Each subject's right forearm (dominant hand) underwent a computed tomography (CT) scan to create 3D surface models of the ulna and radius. Each subject was imaged using a calibrated biplanar radiographic system at 90° pronation, 45° pronation, neutral, 45° supination, and 90° supination while the elbow was in extension or flexion. The 3D positions of the radius and ulna were obtained using a 2D-to-3D image registration method. The relative translations of the radius in the radioulnar, dorsopalmar, and proximodistal directions and the relative rotations of the radius about the radioulnar, dorsopalmar, and proximodistal axes were evaluated with respect to the ulna during pronation and supination. In general, the radius translated towards the ulnar side throughout forearm rotation, and moved towards the palmar side as pronation increased and moved dorsally as supination increased, and was positioned proximally during pronation and distally during supination. The rotation of the radius was dominant about the proximodistal axis. These kinematic variables were affected by elbow position and sex of the subject. The current findings regarding the 3D kinematics of the DRUJ during forearm pronation and supination may contribute to further understanding of the physiological biomechanics of the upper limb.

DOI： 10.1299/jbse.15-00364

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Most cases of hypophosphatasia (HPP) exhibit early loss of primary teeth. Results of microcomputed tomography (micro-CT) analysis of teeth with HPP have rarely been reported. The purpose of the present study was to describe the mineral density distribution and mapping of exfoliated teeth from an HPP patient using micro-CT. Four exfoliated teeth were obtained from a patient with HPP. Enamel and dentin mineral densities of exfoliated teeth were measured on micro-CT. The mean values of enamel and dentin mineral densities in mandibular primary central incisors with HPP were 1.61 and 0.98 g/cm3, respectively. The corresponding values in the mandibular primary lateral incisors were 1.60 and 0.98 g/cm3, respectively. Enamel hypoplasia was seen in the remaining teeth, both maxillary and mandibular primary canines and first and second molars. Micro-CT enables nondestructive, noninvasive evaluation and is useful for studying human hard tissues obtained from patients.

DOI： 10.1155/2016/4898456

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Micro computed tomography (Micro CT) is an imaging technique widely used for visualizing the internal structure of objects using the x-ray attenuation method. As it enables non-destructive, noninvasive evaluation and three-dimensional analysis, it is useful for various studies of human hard tissues. Most hypophosphatasia cases exhibit early loss of primary teeth, however findings of Micro CT analysis of them have not been reported. The purpose of the present study was to describe the mineral density distribution of exfoliated teeth with hypophosphatasia using Micro CT. Each two exfoliated teeth of mandibular primary central incisors gained from 2 hypophosphatasia patients were investigated for enamel and dentin mineral densities. Mineral density distribution revealed that the case 1 were lower than the homonymous teeth case 2 in the region of enamel edge in enamel and dentinoenamel junction in dentin. These results suggested that hypophosphatasia patients had the variety of hypomineralization in the primary dentition. The investigations using Micro CT is useful for various studies of human hard tissues gained from patients since it enables non-destructive, noninvasive evaluation.

DOI： 10.11395/jjsem.16.122

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In the clinical, it is difficult to carry out the motion analysis because it requires a large place. The purpose of this study is to examine the gait analysis method by one direction frontal video that can be easily measured in clinical. The subjects were five healthy persons attached four markers at both shoulders and both anterior superior iliac spine (ASIS). The walking motion of each subject toward a camera was analyzed. Body trunk tilt and centroid sway of the upper body part were calculated and compared with the results of three-dimensional gait analysis methods. The result showed the same tendency of the body trunk tilt and the centroid sway changes based on each method. The result suggested that the gait analysis by one direction frontal video could evaluate the large abnormal gait. Further, authors evaluated OA knee joint thrust using one direction frontal video. The change of the knee joint alignment and the distance between the loading axis of lower extremity and knee joint center were calculated as knee joint thrust. Results showed that knee adduction angle and distance of knee joint center from lower limb loading axis of OA patient were increased. The result suggested that this method could evaluate the knee joint thrust of OA patient.

DOI： 10.11395/jjsem.16.116

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The posterior cruciate ligament (PCL) functions as the primary restraint to posterior tibial movement and the stabilizer for axial rotation of the knee joint. It is, therefore, important to know the mechanical characteristics of the PCL. The objective of this study was to evaluate the in vivo characteristics of the three-dimensional (3D) deformation and orientation of the PCL during knee flexion using magnetic resonance imaging (MRI). Ten normal knees were visualized using MRI at full extension (FE), 10°, 20°, 30° and 60° of static knee flexion. The length, strain, elevation and deviation of the PCL were measured using the 3D models of the femur, tibia and PCL reconstructed from the MR images. The PCL length was measured in three portions (Medial: M, Central: C, Lateral: L) to consider its 3D shape. Tendencies of the PCL elongation and strain during knee flexion were different among these 3 portions. The PCL length in M portion was shortest in 10° or 20° and extended in FE and 60°. The PCL length in L portion, on the other hand, extended from FE to 60°. These 3D deformation characteristics were consisted with the changes in the elevation and deviation of the PCL during knee flexion.

DOI： 10.11395/jjsem.16.127

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The purpose of this study was to develop a method for evaluation of the three-dimensional (3D) alignment and position of the artificial knee joint using a biplanar slot radiography (SR) system and 3D models. A SR system uses collimated fan beam x-rays synchronized with the movement of a flat-panel detector. This system allows to obtain a full length x-ray image of the body with reduced dose and smaller image distortion compared with conventional x-ray systems. The biplanar SR system used a rotation table positioned at 0 deg and 60 deg relative to the optical axis of an X-ray source. Camera calibration was performed using an acrylic frame with 72 radiopaque markers. The femoral and tibial components of a total knee replacement system were immobilized and imaged using the biplanar SR system. Then, the femoral component was installed on a sawbone femur and imaged again. The 3D positions of the components and femur were recovered using an interactive 2D to 3D image registration method. Overall, the largest estimation errors were within 1 mm in translation and 1 deg in rotation, demonstrating that this method has an adequate accuracy for the clinical usage.

DOI： 10.11395/jjsem.16.134

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER IRELAND LTD  

We recently developed a new method for three-dimensional evaluation of mechanical factors affecting knee joint in order to help identify factors that contribute to the progression of knee osteoarthritis (KOA). This study aimed to verify the clinical validity of our method by evaluating knee joint dynamics during gait. Subjects were 41 individuals (14 normal knees; 8 mild KOAs; 19 severe KOAs). The positions of skin markers attached to the body were captured during gait, and bi-planar X-ray images of the lower extremities were obtained in standing position. The positional relationship between the markers and femorotibial bones was determined from the X-ray images. Combining this relationship with gait capture allowed for the estimation of relative movement between femorotibial bones. We also calculated the point of intersection of loading axis of knee on the tibial proximal surface (LAK point) to analyze knee joint dynamics. Knee flexion range in subjects with severe KOA during gait was significantly smaller than that in those with normal knees (p = 0.011), and knee adduction in those with severe KOA was significantly larger than in those with mild KOA (p &lt; 0.000). LAK point was locally loaded on the medial compartment of the tibial surface as KOA progressed, with LAK point of subjects with severe KOA rapidly shifting medially during loading response. Local loading and medial shear force were applied to the tibial surface during stance phase as medial KOA progressed. Our findings suggest that our method is useful for the quantitative evaluation of mechanical factors that affect KOA progression. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gaitpost.2015.04.018

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The purpose of the present study was to develop a novel-designed phantom that could be scanned with a sample in the same image, that specialize for quantitative analyses of human dentin mineral density using the X-ray attenuation method. A further attempt was made to demonstrate the intracoronal dentin mineral density using this phantom in mandibular incisors. The phantom prepared with a 15 mm hole in the center of an acrylic resin bar having an outside diameter of 25 mm and 8 small holes (diameter, 3 mm) were made at equal intervals around the center. Liquid dipotassium hydrogen phosphate (K2HPO4) solutions were established at 0.4, 0.6, 0.8 and 1.0 g/cm(3), and were arranged to these holes. The mean value of the intracoronal dentin mineral density was 1.486 +/- 0.016 g/cm(3) in the present study. As the results of the present study corresponded to previous reports, this new phantom was considered to be useful. This phantom enables the analysis of samples that are not readily available by conventional mechanical tests and may facilitate biomechanical investigations using X-ray images. It was suggested that this system is a simple, accurate and novel mineralization measuring system.

DOI： 10.3233/BME-151545

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DOI： 10.11395/jjsem.14.s291

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Automated methods for constructing patient-specific anatomical coordinate systems (ACSs) for the pelvis, femur and tibia were developed based on the bony geometry of each, derived from computed tomography (CT). The methods used principal axes of inertia, principal component analysis (PCA), cross-sectional area, and spherical and ellipsoidal surface fitting to eliminate the influence of rater's bias on reference landmark selection. Automatic ACSs for the pelvis, femur, and tibia were successfully constructed on each 3D bone model using the developed algorithm. All constructions were performed within 30 s; furthermore, between- and within- rater errors were zero for a given CT-based 3D bone model, owing to the automated nature of the algorithm. ACSs recommended by the International Society of Biomechanics (ISB) were compared with the automatically constructed ACS, to evaluate the potential differences caused by the selection of the coordinate system. The pelvis ACSs constructed using the ISB-recommended system were tilted significantly more anteriorly than those constructed automatically (range, 9.6-18.8 degrees). There were no significant differences between the two methods for the femur. For the tibia, significant differences were found in the direction of the anteroposterior axis; the anteroposterior axes identified by ISB were more external than those in the automatic ACS (range, 17.5-25.0 degrees). (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jbiomech.2013.12.013

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

The range of motion (ROM) resulting from total hip arthroplasty (THA) depends on the relative orientation of the femoral and acetabular components, and malpositioning of components is a possible cause of several complications. The purpose of this study was to validate a 3-dimensional (3D) lower extremity alignment assessment system (3D LAAS) for the measurement of alignment of natural and implanted hip joints and implant position with respect to the target bone with the subject in a standing position. Sawbone femur and pelvis and femoral and acetabular components of a total hip arthroplasty system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the 3D bone models and component computer-aided design models were projected onto extracted contours of the femur, pelvis, and implants in calibrated frontal and oblique X-ray images. The 3D position of each model was recovered by minimizing the differences between projected outlines and contours. Mean absolute errors were less than 1.27 ± 0.79 mm and 0.99 ± 0.52° for femur and pelvis, 1.64 ± 0.66 mm and 1.54 ± 0.39° for femoral and acetabular components, 1.58 ± 0.29 mm and 1.75 ± 0.69° for femur and femoral component, and 1.51 ± 0.49 mm and 1.24 ± 0.14° for pelvis and acetabular component, indicating that the 3D LAAS is applicable to measure the alignment of natural and implanted hip joints and implant position after THA.

DOI： 10.1299/jbse.13-00162

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While various factors have been assumed to affect knee joint biomechanics, few data have been reported on the function of the extensor mechanism in deep flexion of the knee. This study analyzed the patellofemoral joint contact kinematics and the ratio of the quadriceps and patellar tendon forces in living subjects when they performed a single leg lunge up to 150 deg of flexion. The data revealed that in the proximal-distal direction, the patellofemoral articular contact points were in the central one-third of the patellar cartilage. Beyond 90 deg of flexion, the contact points moved towards the medial-lateral edges of the patellar surface. At low flexion angles, the patellar tendon and quadriceps force ratio was approximately 1.0 but reduced to about 0.7 after 60 deg of knee flexion, implying that the patella tendon carries lower loads than the quadriceps. These data may be valuable for improvement of contemporary surgical treatments of diseased knees that are aimed to achieve deep knee flexion.

DOI： 10.1115/1.4024284

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：新潟大学  

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This study quantified in-vivo 3D patellar tendon kinematics during weight-bearing deep knee bend beyond 150 degrees. Each knee was MRI scanned to create 3D bony models of the patella, tibia, femur, and the attachment sites of the patellar tendon on the distal patella and the tibial tubercle. Each attachment site was divided into lateral, central, and medial thirds. The subjects were then imaged using a dual fluoroscopic image system while performing a deep knee bend. The knee positions were determined using the bony models and the fluoroscopic images. The patellar tendon kinematics was analyzed using the relative positions of its patellar and tibial attachment sites. The relative elongations of all three portions of the patellar tendon increased similarly up to 60 degrees Beyond 60 degrees, the relative elongation of the medial portion of the patellar tendon decreased as the knee flexed from 60 degrees to 150 degrees while those of the lateral and central portions showed continuous increases from 120 degrees to 150 degrees. At 150 degrees, the relative elongation of the medial portion was significantly lower than that of the central portion. In four of seven knees, the patellar tendon impinged on the tibial bony surface at 120 degrees and 150 degrees of knee flexion. These data may provide useful insight into the intrinsic patellar tendon biomechanics during a weight-bearing deep knee bend and could provide biomechanical guidelines for future development of total knee arthroplasties that are intended to restore normal knee function. (c) 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:15961603, 2012

DOI： 10.1002/jor.22126

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

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The purpose of the present study was to examine the fracture toughness and Vickers microhardness number of permanent and primary human enamel using the indentation microfracture method. Crack resistance and a parameter indirectly related to fracture toughness were measured in 48 enamel specimens from 16 permanent teeth and 12 enamel specimens obtained from six primary teeth. The Vickers microhardness number of the middle portion was greater than the upper portion in primary enamel. The fracture toughness was highest in the middle portion of permanent enamel, because fracture toughness greatly depends upon microstructure. These findings suggest that primary teeth are not miniature permanent teeth but have specific and characteristic mechanical properties.

DOI： 10.1007/s10856-012-4678-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

This paper deals with the applicability of the near infrared (NIR) spectroscopy to quantitative measurement of the water content in human articular cartilage using gelatin model. We developed the device using NIR light at a wave length of 970nm, and investigated whether or not the device was useful for the measurement of the water content in articular cartilage. The gelatin was used as materials for the specimens with single, two- and three-layers. The absorbance defined as the intensity ratio between emitting and receiving NIR lights, the variation of receiving light intensity with the water content, and that with the distance between two probes of the light source and sensor were measured. The absorbance increased with increasing water content and with increasing probe distance (R<SUP>2</SUP>=0.86&sim;0.91). In the layered specimens, the light was supposed to pass through the surface layer and then reach the adjacent layer. These results showed that the device was useful for the measurement of the water content in the single and layered specimens. This study suggested that the device developed in this study have some possibilities of acquiring the quantitative data of water content at any point from the surface of articular cartilage.

DOI： 10.11395/jjsem.11.s239

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Other Link： http://hdl.handle.net/10191/26369

Language：Japanese   Publisher：日本実験力学会  

The modern and widely known artificial hip joint developed by John Charnley in the 1970s consisted of three parts, 1. a metallic femoral stem, 2. a UHMWPE acetabular liner, 3. a metallic acetabular socket or bone cement. Acetabular liner has a bearing surface of UHMWPE which has a low coefficient of friction and low wear rate. In the long term, wear particulate dose accumulate and lead to a condition known as osteolysis, which leads to bone loss, joint loosening, discomfort, and ultimately limits the lifespan of the artificial joint. Therefore, the evaluation of the wear on acetabular bearings, which depends directly on contact pressure, is essential to analyze the failure of the acetabular implant, as well as for a better design of artificial joint. The objective of the present study was to develop a method of applying discrete element analysis (DEA) based on rigid-body-spring-model (RBSM) to artificial hip joint, using patient-specific 3D bone model and motion capture data, and to analyze the stress distribution on bearing surface during gait motion. The two peaks in peak stress were observed with a maximum value of 12.3 MPa and the corresponding contact area was 21.8% of total bearing area, and small contact area less than 25% at the edge of the superior bearing surface was observed during gait motion.

DOI： 10.11395/jjsem.11.112

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DOI： 10.11395/jjsem.11.112

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

The wrist joint is condyloid and capable of movement through two axes: palmar/dorsal flexion and radial/ulnar deviation. Knowledge of <i>in vivo</i> joint mechanics is important for understanding pathological mechanisms and the treatment of various joint problems. The purpose of this study was to investigate the <i>in vivo</i> wrist joint mechanism during wrist motion. <i>In vivo</i> wrist joint contact and the kinematics of the scaphoid and lunate during palmar/dorsal flexion and radial/ulnar deviation were examined using magnetic resonance imaging (MRI). The wrist joints of 15 healthy young volunteers were scanned at 8 positions (.30 deg of palmar flexion; neutral; 30, 60, and 90 deg of dorsal flexion; .20 deg of radial deviation; neutral; and 20 deg of ulnar deviation). Contact of the wrist joint was estimated quantitatively from the derived MR images. Using three-dimensional surface models of the carpal bones, the kinematics of the scaphoid and lunate were analyzed three-dimensionally.

DOI： 10.11395/jjsem.10.s261

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Other Link： http://hdl.handle.net/10191/26375

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DOI： 10.11395/jjsem.10.s234

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

Currently, stem insertion during total hip arthroplasty (THA) is not well controlled. The present study investigated a method for improving stem setting in accordance with preoperative planning using a three-dimensional (3-D) computed tomography (CT) model of the femur and RGB images of the excised femoral head. We utilized three femoral heads removed during THA and modeled each head using three spherical acrylic markers. Each femoral head was osteotomized using a parallel jig and three rectangular images of the osteotomized head were taken using a CCD camera. Each femoral head was then set on a camera base and RGB images were taken from three orthogonal directions using the CCD camera. The B-images of the femoral head and the 3-D bone model were processed through image-matching software using an automatic outline extraction and downhill simplex method. The position of the contralateral side of the jig, related to the femur, was measured using a 3-D measuring system in order to validate the accuracy of the image-matching. However, since validation of the accuracy of the image-matching is difficult once the femoral head is excised, a six-degree-of-freedom board was used to facilitate the accuracy validation.

DOI： 10.11395/jjsem.10.s247

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

Estimation of the artificial hip joint contact area and pressure distribution during motions of daily life is important in predicting joint degeneration mechanism and implant wear. The purpose of this study was to develop a method of applying discrete element analysis (DEA) based on a rigid body spring model to artificial hip joint, and to analyze contact area and pressure distribution during different motions. Post-operative motion analyses of four basic motions, such as fast walking, slow walking, standing up and sitting down were performed by using VICON system and Kistler force plate. Implant orientation was obtained by matching the contours of 3D bone model and implant CAD model to those of the biplanar CR images. Triangular mesh at interior surface of cup model was considered as liner surface and used for applying DEA to artificial hip joint.Because stem model was considered to be a rigid body and consequential transformations occurred only inside the liner model, triangular mesh was considered to be a compressive spring respectively.The change of contact area and the pressure distribution under dynamic condition were calculated easily through these considerations, and rapid increase accompanied with change of area was observed in knee bending motions.

DOI： 10.11395/jjsem.10.s251

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Other Link： http://hdl.handle.net/10191/26374

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

An automated image-matching technique is presented to assess alignment of the entire lower extremity for normal and implanted knees and the positioning of implants with respect to bone. Sawbone femur and tibia and femoral and tibial components of a total knee arthroplasty system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the three-dimensional (3D) bone models and component computer-aided design (CAD) models were projected onto extracted contours of the femur, tibia, and implants in frontal and oblique X-ray images. Three-dimensional position of each model was recovered by minimizing the difference between the projected outline and the contour. Median values of the absolute error in estimating relative positions were within 0.5 mm and 0.6 degrees for the femur with respect to the tibia, 0.5 mm and 0.5 degrees for the femoral component with respect to the tibial component, 0.6 mm and 0.6 degrees for the femoral component with respect to the femur, and 0.5 mm and 0.4 degrees for the tibial component with respect to the tibia, indicating significant improvements when compared to manually obtained results. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jbiomech.2009.08.022

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Language：Japanese   Publisher：公益社団法人 日本放射線技術学会  

Elevated contact stress on the articular joints has been hypothesized to contribute to articular cartilage wear and joint pain. However, given the limitations of using contact stress and areas from human cadaver specimens to estimate articular joint stress, there is need for an &lt;i&gt;in vivo&lt;/i&gt; method to obtain such data. Magnetic resonance imaging (MRI) has been shown to be a valid method of quantifying the human joint contact area, indicating the potential for &lt;i&gt;in vivo&lt;/i&gt; assessment. The purpose of this study was to describe a method of quantifying the tibiofemoral joint contact area using MRI. The validity of this technique was established in porcine cadaver specimens by comparing the contact area obtained from MRI with the contact area obtained using pressure-sensitive film (PSF). In particular, we assessed the actual condition of contact by using the ratio of signal intensity of MR images of cartilage surfaces. Two fresh porcine cadaver knees were used. A custom loading apparatus was designed to apply a compressive load to the tibiofemoral joint. We measured the contact area by using MRI and PSF methods. When the ratio of signal intensity of the cartilage surface was 0.9, the error of the contact area between the MR image and PSF was about 6%. These results suggest that this MRI method may be a valuable tool in quantifying joint contact area&lt;i&gt; in vivo&lt;/i&gt;.

DOI： 10.6009/jjrt.65.1407

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

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DOI： 10.11395/jjsem.9.s167

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Dynamic nanoindentation was used to determine microstructural viscoelastic properties of single osteons and interstitial lamellae of rat cortical bone tissue. The effects of mineral, organic and water contents on macrostructural viscoelastic properties were also investigated. Compared to interstitial lamellae, the storage moduli of osteons were significantly lower; however, loss tangents were higher. The storage modulus and mineral content were correlated, and the loss tangent and the organic and water contents were linearly correlated.

DOI： 10.11395/jjsem.9.s151

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DOI： 10.11395/jjsem.9.s162

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The purpose of the present study is to develop a direct and accurate method for measuring knee kinematics by using single-plane fluoroscopy. The study was carried out on a human cadaver femur. Computed tomography (CT) scan data of the femur was taken in order to construct 3D bone volume model of the femur. The femur was placed on an acrylic holder that was attached to a micromanipulator. The femur was rotated about in each orthogonal axis of the micromanipulator over a range of ±2° in 1° increments and then translated along each orthogonal axis over a range of ±2 mm in 1-mm increments. The 3-dimensional (3D) position of the femur (in other words, the 6 degree-of-freedom (DOF) parameters) was recovered by matching the digitally reconstructed radiographs (DRRs) generated from the 3D volume model of the femur and single-plane fluoroscopic images taken from the 25 positions generated by using the micromanipulator. The root-mean-square error (RMSE) of the overall rotation parameters was within 1.4°. For the translation parameters RMSE took its maximal value of 7.8 mm in the out-of-plane direction. This indicates that the present method has potential for clinical application. Copyright © 2009 by The Japan Society of Mechanical Engineers.

DOI： 10.1299/jbse.4.192

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Language：English   Publisher：The Japanese Society of Pediatric Dentistry  

47, XYY is a sex chromosome-number disorder occurring in males. Pediatric dentists seldom report encountering 47, XYY males, probably because there are no overt signs of the disease. The purpose of this report is to present the clinical oro-facial findings of the case of a 47, XYY boy based on cephalometric analysis and study model examinations as well as micro-CT measurement of tooth mineralization. An 11-year-old Japanese boy was referred to our clinic for extraction of primary teeth because of their prolonged retention. He had 47, XYY disorder, pulmonary hypertension, and slight mental retardation. Cephalometric analysis and study model examinations that included a comparison of tooth size and arch assessments were performed. A further attempt was made to demonstrate the degree of dentin mineralization in primary molars. The boy&rsquo;s height and weight were normal but his head circumference had exceeded the 94th percentile since 2 years of age. The cephalometric analysis showed an increase in the lower facial height and bimaxillary protrusion with a longer mandible. Study model examination revealed that the mesio-distal crown widths of all erupted primary and permanent teeth were larger than the standard values, except for the mandibular permanent canines. The degree of dentin mineralization was almost normal in the crown and root areas. A profilogram showed an increase in the lower facial height and bimaxillary protrusion with a longer mandible. The dental arch showed a remarkably contracted width but an extended length. The crown width was larger than the standard values, but the distribution of the degree of dentin mineralization differed little from normal.

DOI： 10.11411/pdj.18.179

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本材料学会  

The effects of low-gamma irradiation on the impact compressive properties of ultra high molecular weight polyethylene (UHMWPE) were investigated. Gamma irradiation was performed at 30kGy in nitrogen or at 29kGy in air without post-irradiation treatment. Impact compressive tests using the split-Hopkinson pressure-bar (SHPB) technique were performed to measure stress-strain relations up to a true strain of 8% at a strain rate of 260s-1. Gamma irradiation in air significantly increased the Young's modulus and the 0.5% yield stress, and gamma irradiation in N2 significantly increased the 0.5% yield stress, as determined by impact compressive testing. The impact stress-strain behaviors of both unirradiated and gamma irradiated UHMWPE specimens were compared by the elasto-viscoplastic model proposed by Bergström [Biomaterials Vol.23 p.2329 (2002)]. We found that the elasto-viscoplastic model had a potential to predict the observed impact stress-strain responses. © 2008 The Society of Materials Science.

DOI： 10.2472/jsms.57.882

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Science Council of Japan  

We consider an axisymmetric elastic contact problem of a transversely isotropic layer which is bonded to a rigid foundation. The upper surface of the layer is smoothly indented by a flat-ended circular rigid punch. The problem is reduced to an analytical and exact solution of an infinite system of simultaneous equations utilizing a method of expressing a normal contact stress on the punch as an appropriate series function with a singularity at the punch edge. Convergence can be achieved using 8 terms of the series. Numerical results are obtained to examine the effects of the layer thickness and material anisotropy on stress fields.

DOI： 10.11345/nctam.56.15

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHURCHILL LIVINGSTONE INC MEDICAL PUBLISHERS  

We developed a quantitative 3-dimensional (3D) technique for the assessment of changes in the tibial joint line as well as distal and posterior femoral joint lines using a 3D image-matching procedure. In this study, we performed 3D joint line assessment of 20 knees that had undergone total knee arthroplasty. most of the knees exhibited proximal change in the tibial joint line, distal change in the distal femoral joint line, and anterior change in the posterior femoral joint line. There were clear differences in changes in the joint lines between the medial and lateral condyles. The findings indicate that changes in the joint line should be individually assessed for each condyle and that the assessment should include not only the tibial condyle but also the distal and posterior femoral condyles.

DOI： 10.1016/j.arth.2006.06.020

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The effects of strain rate and low-gamma irradiation on the compressive properties of ultra-high molecular-weight polyethylene (UHMWPE) were investigated. Gamma irradiation was performed at 30 kGy in nitrogen or at 29 kGy in air without post-irradiation treatment. Quasi-static and impact compressive tests using the split-Hopkinson pressure-bar technique were performed to measure stress-strain relations up to a true strain of 8% at strain rates of between 0.0004 and 260 s(-1). For both unirradiated and gamma-irradiated UHMWPE specimens, an increase in the strain rate significantly increased the Young's modulus and the 0.5% yield stress. Gamma irradiation in air significantly increased the Young's modulus, as determined by quasi-static and impact compressive testing, and the 0.5% yield stress, as determined by impact compressive testing. The strain-rate dependence in the power-law relationship was similar to that observed for strain rates ranging from 0.02 to 0.10 s(-1) (Kurtz et al., Biomaterials 23, 2002, pp. 3681-3697).

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The response of wall stress to the elasticity of each layer in the aorta wall was investigated to understand the role of the different elastic properties of layers in the aortic dissection. The complex mechanical interaction between blood flow and wall dynamics in a three-dimensional arch model of an aorta was studied by means of computational coupled fluid-structure interaction analysis. The results show that stresses in the media layer are highest in three layers and that shear stress is concentrated in the media layer near to the adventitia layer. Hence, the difference in the elastic properties of the layers could be responsible for the pathological state in which a tear splits across the tunica media to near to the tunica adventitia and the dissection spreads along the laminar planes of the media layer where it is near the adventitia layer.

DOI： 10.1007/s10867-006-9027-7

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DOI： 10.11345/nctam.55.61

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DOI： 10.11395/jjsem.6.13

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Language：Japanese   Publisher：日本実験力学会  

This study analyzed tibio-femoral joint kinematics and contact area during knee flexion at 0&amp;deg;, 30&amp;deg;, 60&amp;deg;, 90&amp;deg; and 135&amp;deg; using magnetic resonance imaging with a 3D-fat-suppressed fast low angle shot sequence (3D-FLASH). At a 200N loading situation, knee flexion angles were chosen to be 0&amp;deg;, 30&amp;deg;and 60&amp;deg;. Sagittal and coronal images were obtained under the loading and unloading situations from 6 healthy male Japanese volunteers. At unloading situation, from 0&amp;deg; to 90&amp;deg; the centroids of the medial and lateral contact areas translated backward and outside. From 90&amp;deg; to 135&amp;deg; the centroids of the medial and lateral contact areas translated backward and inside. The contact areas tended to decrease, but from 60&amp;deg; to 135&amp;deg; knee flexion the medial contact area was not changed generally. At loading situation, almost the same results as observed at unloading situation for each translation were obtained. However, the translation of centroids of the medial and lateral contact areas decreased with an increase of knee flexion, and the centroids moved roughly straight backward as well. The contact areas increased at each knee flexion angle as compared to unloading situation. These results showed good correlation with previous ones found in the other studies of knee kinematics.

DOI： 10.11395/jjsem.6.31

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：MEDIMOND S R L  

This study analyzed tibio-femoral(TF) joint kinematics and contact area(CA) during knee flexion at 0 degrees, 30 degrees, 60 degrees, 90 degrees and 135 degrees using MRI. At a 200N loading situation, knee flexion angles were chosen to be 0 degrees, 30 degrees and 60 degrees. At unloading situation, from 0 to 90 the centroids of the medial and lateral CAs were translated backward and outside. From 90 degrees to 135 degrees, the centroids of both CAs translated backward and inside. The CAs tended to decrease, but from 60 degrees to 135 degrees knee flexion the medial CA was not changed generally. At loading situation, almost the same results as observed at unloading situation for each translation were obtained. However, the translation of the centroids of both CAs decreased with an increase of knee flexion. The CAs increased at each knee flexion angle as compared to unloading situation.

DOI： 10.11395/jjsem.6.31

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This study analyzed tibio-femoral(TF) joint kinematics and contact area(CA) during knee flexion at 0 degrees, 30 degrees, 60 degrees, 90 degrees and 135 degrees using MRI. At a 200N loading situation, knee flexion angles were chosen to be 0 degrees, 30 degrees and 60 degrees. At unloading situation, from 0 to 90 the centroids of the medial and lateral CAs were translated backward and outside. From 90 degrees to 135 degrees, the centroids of both CAs translated backward and inside. The CAs tended to decrease, but from 60 degrees to 135 degrees knee flexion the medial CA was not changed generally. At loading situation, almost the same results as observed at unloading situation for each translation were obtained. However, the translation of the centroids of both CAs decreased with an increase of knee flexion. The CAs increased at each knee flexion angle as compared to unloading situation.

DOI： 10.11395/jjsem.6.31

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DOI： 10.11345/nctam.54.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：W B SAUNDERS CO-ELSEVIER INC  

Purpose: To investigate differences in contact pressure in the bone tunnel between the inside-out and outside-in techniques used for anterior cruciate ligament reconstruction. Type of Study: In vitro cadaveric analysis. Methods: Four fresh-frozen cadaver knees were tested. A femoral tunnel was generated through the tibial tunnel (inside-out technique). Another femoral tunnel was created using a rear-entry guide at the same intra-articular exit (outside-in technique). Aluminum cylinders containing 4-way (anterior, posterior, medial, and lateral) conductive rubber pressure sensors at the entrance of the joint were inserted into the tibial and femoral tunnels. Dynamic changes in the contact pressure of grafts in the femoral and tibial tunnels during 0 degrees to 130 degrees of knee flexion were measured. Results: Contact pressure of the graft migrated from the anterior to the posterior portion of the femoral tunnel upon alignment of the femoral and tibial tunnels. At 0 degrees, 30 degrees, and 60 degrees of knee flexion, significantly greater contact pressure was observed at the anterior portion of the femoral tunnel made by the inside-out technique compared with that in the tunnel made by the outside-in technique. At 0 degrees, 30 degrees, and 60 degrees of knee flexion, significantly greater contact pressure was observed at the lateral portion of the femoral tunnel made by the outside-in technique. Constant contact pressure was observed in the medial portion of the tunnel made by the inside-out technique. Pressure changes in the tibial tunnel were slight; moreover, changes were not influenced by the femoral tunnel direction under any conditions. Conclusions: This study shows that contact pressure in the femoral tunnel is influenced by the direction of the femoral tunnel. Clinical Relevance: The femoral tunnel direction in anterior cruciate ligament reconstruction is an important factor for femoral tunnel enlargement. A horizontal direction of the femoral tunnel might be needed for mature bone graft incorporation.

DOI： 10.1016/j.arthro.2004.12.007

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：日本実験力学会  

The mechanical properties of cortical bone are a consequence of the interaction between the mineral and collagen components. Small variations in the amount of mineral present in a section of bone can have a large influence on its mechanical properties. Studies have shown the correlations between Vickers microhardness and mineral content, and Vickers microhardness and elastic modulus using three-point and four-point bending tests. However, the precise nature of statistical relationship has yet to be established. Nanoindentation, which evolved from Vickers microhardness test, allows for measurement of mechanical properties of cortical bone at the nanometer scale. The nanoindentation technique has been applied to estimate mechanical properties of bone at a microscopic length scale, overcoming the limitations of traditional mechanical tests for small specimens. In this study, the relationships between mechanical properties measured by nanoindentation and volumetric Bone Mineral Density (vBMD) measured by peripheral Quantitative Computed Tomography (pQCT) in femoral cortical bone from a variety of ages of rats were investigated. The specimen of rat cortical bone used here was Haversian bone. Experimentally measured elastic modulus was correlated with vBMD (r=0.80). It was found that a good correlation also existed between hardness and vBMD (r=0.81).

DOI： 10.11395/jjsem.5.40

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DOI： 10.11345/nctam.53.27

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Ten fresh-frozen cadaveric ankles were studied to investigate the effect of an ankle brace (Air-Stirrup) on the three-dimensional (3-D) motion and contact-pressure distribution of the talo-tibial joint with lateral ligamentous injury. Three-dimensional motion and contact-pressure distribution were simultaneously measured under dynamic conditions employing a direct linear-transformation technique and a dynamic-pressure sensor, respectively. Inversion increased significantly upon severing of the anterior talofibular (ATF) ligament and calcaneo-fibular (CF) ligaments; however, restoration to the intact level was observed following application of the ankle brace. Internal rotation also increased upon severing of the lateral ligaments in the plantar flexion; however, this difference was not altered by using the ankle brace. The contact area on the articular surface of the talus shifted from posterior to anterior between plantar flexion and dorsal flexion; additionally, a high pressure area was evident in the medial aspect of the talus following severing of the lateral ligaments. Upon application of the ankle brace, however, no significant changes were apparent in the contact condition. The results of this study suggest that stabilization against inversion is the major function of braces in terms of protection of ankle sprains. Ankle sprains, however, often occur in combinations of inversion, plantar flexion and internal rotation; therefore, restriction of plantar flexion and internal rotation may also be an important function of the ankle brace.

DOI： 10.1007/s00167-004-0493-9

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Language：Japanese   Publisher：日本実験力学会  

Mechanical properties of ultra high molecular weight polyethylene (UHMWPE) used as a bearing material in total joint replacement system have been investigated under impact compressive load. Ten cylindrical specimens, 8mm in both diameter and length, were machined from compression molded UHMWPE rods. Half of these specimens were gamma-irradiated in air at a dose of 2.9 Mrad without post irradiation treatment. Impact compression tests were performed using the split-Hopkinson pressure-bar technique to evaluate dynamic stress-strain relation up to 8% strain at a strain rate of about 400s-1. For both gamma-irradiated and unirradiated specimens, stress-strain relations exhibited relatively linear portions up to 2% strains and the gradients eventually decreased with increasing strain. Young&#039;s modulus determined from the linear portion and 0.5% yield stress were significantly higher for gamma-irradiated specimens than for unirradiated specimens. Two-dimensional elasto-plastic stress and strain analysis of hip prosthesis was performed under impact loading using a finite element method. Results indicated that the increase in mechanical properties induced by gamma irradiation reduced plastic strain within the UHMWPE cup.

DOI： 10.11395/jjsem2001.3.225

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ORTHOPAEDIC SOC SPORT MED  

Background: The causes of bone tunnel enlargement after anterior cruciate ligament reconstruction have not been thoroughly investigated.
Hypothesis: A malpositioned femoral tunnel and an acute femoral tunnel angle may increase the mechanical stress in the femoral tunnel.
Study Design: Controlled laboratory study. Methods: Three femoral tunnels (normal, anterior, and acute) and the tibial tunnel were made in four fresh-frozen cadaveric knees. Aluminum cylinders containing pressure-sensitive conductive rubber sensors at the joint entrance were inserted into the femoral tunnels. Dynamic changes in the contact pressure of the graft in the femoral tunnel were measured.
Results: Peak contact pressures and dynamic changes in contact pressure for the normal and anterior femoral tunnels demonstrated no differences. Maximum contact pressure of the graft was observed at the anterior portion with the knee in full extension and at the posterior portion with deep knee flexion. Consistent contact pressure occurred at the anterior aspect of the acute femoral tunnel throughout the range of motion. Mean contact pressure at the anterior region of the acute femoral tunnel was significantly higher than that of the normal femoral tunnel at 60degrees, 90degrees, and 120degrees of knee flexion.
Conclusions: The consistent contact pressure in the anterior aspect of the acute femoral tunnel may erode the anterior portion of the femoral tunnel, resulting in bone tunnel enlargement.
Clinical Relevance: The femoral tunnel direction in anterior cruciate ligament reconstruction is an important factor in reducing femoral tunnel enlargement. (C) 2003 American Orthopaedic Society for Sports Medicine.

DOI： 10.1177/03635465030310032001

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This study examines the axisymmeteric problem on an elastic layer with a penny-shaped crack situated in its middle plane. The crack surfaces are subjected to uniform pressures. The layer surfaces are free from stresses for case I while smooth-clamp conditions are prescribed on the layer surfaces for case II. By assuming series expansions for the normal displacement on the crack surfaces, both cases are reduced to analytical and exact solutions through infinite system of simultaneous equations. An expression for the stress intensity factor at the penny-shaped crack is evaluated in a simple form of a series which involves coefficients of the solutions of the simultaneous equations. Numerical results are obtained to examine the effects of the layer thickness and boundary conditions of the layer surfaces. on norma I stress and displacement distributions and on the stress intensity factors.

DOI： 10.1299/jsmea.46.10

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Mechanical properties of ultra high molecular weight polyethylene (UHMWPE) used as a bearing material in total joint replacement system have been investigated under impact compressive load. Ten cylindrical specimens, 8mm in both diameter and length, were machined from compression molded UHMWPE rods. Half of these specimens were gamma-irradiated in air at a dose of 2.9 Mrad without post irradiation treatment. Impact compression tests were performed using the split-Hopkinson pressure-bar technique to evaluate dynamic stress-strain relation up to 8% strain at a strain rate of about 400s-1. For both gamma-irradiated and unirradiated specimens, stress-strain relations exhibited relatively linear portions up to 2% strains and the gradients eventually decreased with increasing strain. Young&#039;s modulus determined from the linear portion and 0.5% yield stress were significantly higher for gamma-irradiated specimens than for unirradiated specimens. Two-dimensional elasto-plastic stress and strain analysis of hip prosthesis was performed under impact loading using a finite element method. Results indicated that the increase in mechanical properties induced by gamma irradiation reduced plastic strain within the UHMWPE cup.

DOI： 10.11395/jjsem2001.3.225

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The purpose of this study was to clarify the dynamic changes in contact pressure distribution and three-dimensional ankle joint motion before and after lateral ligament injuries. Five fresh and frozen intact cadaveric ankles were examined. Each ankle was mounted on a specially designed frame that preserved five degrees of freedom motion. The direct linear transformation technique was used to measure the three dimensional ankle motion, and a pressure-sensitive conductive rubber sensor was inserted into the talocrural joint space to determine the contact pressure distribution. The contact area on the talus for intact ankle moved anteriorly and laterally with increasing dorsiflexion. An area of high pressure was observed in the medial aspect of the articular surface after the ligament was cut. Supination significantly increased after a combined anterior talofibular ligament (ATF) and calcaneofibular ligament (CF) were cut in comparison with after only an ATF was Cut, and no significant differences were observed in motional properties tinder each experimental condition.

DOI： 10.1299/jsmec.44.1082

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DOI： 10.11345/nctam.50.97

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DOI： 10.11345/nctam.50.91

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with the attenuation of impact load through patella-patellar tendon-tibial tuberosity (PTT) complex with respect to the progress of ossification of growing cartilage in tibial tuberosity. Materials used in this study were PTT complexes and patellar tendons taken from porcine hind legs with three different stages of ossification of tibial tuberosity. Their stages of ossification were represented by body weight (20, 100, and 200kgf). Impact tensile tests on PTT complexes and patellar tendons were performed at room temperature using the split-Hopkinson pressure bar technique. In both tests on PTT and patellar tendons, pretensile loads were applied to them just before an application of impact load. The experimental load transmission ratio of PTT complexes increased with an increase of pretension, independent of body weight. Larger body weight, or highly ossified PTT complex appeared to show lower load transmission ratio. Significant change in Young's modulus of patellar tendon with an increase of pretension as well as the progress of ossification of growing cartilage in tibial tuberosity was not found. Impact response analyses were also performed for the prediction of load transmission ratio as well as the section subjected to maximum strain in PTT complexes with different stages of ossification based on the one-dimensional wave propagation theory. The results obtained from the dynamic analyses well corresponded to the location of injuries in different stages of growing process, while static analyses could not predict such clinical situation.

DOI： 10.1299/jsmeatemapcfs.1.01.203.0_493

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

The Vickers microhardness, elastic modulus, bending strength and mineral density of ninety cortical bone specimens from ten bovine femora were determined. The relationship between Vickers microhardness number and elastic modulus was found to be approximately linear. Similar relationship existed between Vickers microhardness and bending strength. The bone mineral density of the plexiform bone was also correlated with microhardness. These relationships found suggest that Vickers microhardness was a good predictor of the elastic modulus, bending strength and mineral density of cortical bone.

DOI： 10.1299/jsmeatemapcfs.2.01.03.0_884

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：VSP BV  

Several kinds of knee motion simulator systems have been developed for the accurate analysis of knee biomechanics. Knee motion simulators, however, are not recognized For their practical use because of difficulties in design and control. Tn this study, a wire-driven knee simulator which generates physiological knee motion has been developed. Physiological three-dimensional tibia motion against the femur can be generated by the simulator. Many clinical studies have been performed to analyze the length displacement pattern of the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). We assume that the physiological knee motion can be realized if the length displacement patterns of the ACL and PCL against the knee flexion angle are the same as the experimental data obtained from the literature. A fuzzy neural control policy, one of the most effective intelligent control policies, has been applied for control of the simulator. Applying the fuzzy neural control policy, human knowledge and experience can be reflected and adaptive/learning ability can be incorporated in the controller. On-line learning of the fuzzy neural controller is carried our to minimize a fuzzy controlled evaluation function using the back-propagation learning algorithm. The effectiveness of the proposed simulator has been evaluated by experiments using a model bone.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Pressure distribution along the contact surface of an articulating joint model was analyzed using different numerical and analytical methods: a discrete rigid element method [rigid-body-spring-model (RBSM)], the finite element method (FEM), a simplified elasticity solution (SES) and the modified Hertzian (MH) theory. The FEM and MH methods modeled joints interposed with elastic layers, while the RBSM and SES methods assumed a simplified joint with a rigid convex indenter on an elastic concave surface. Results for an axisymmetric joint model indicate that all of these methods predict similar pressure distributions on joint surfaces. In non-axisymmetric deformation mode, the RBSM method and FEM calculation showed good agreement in contact pressure prediction. Compared to the other three methods, the RBSM is relatively simple and effective in predicting joint contact pressure under symmetric and non-symmetric loading. The computational efficiency of the RBSM method is particularly attractive for pre-operative planning of reconstructive surgical procedures in orthopaedics in which geometric changes dictate the eventual outcome of the surgery. (C) 1997 Elsevier Science Ltd.

DOI： 10.1016/S0021-9290(97)00009-2

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A new mathematical method was developed to study the indentation problem of an infinite elastic layer overlaid on a rigid foundation. Rigid, flat-ended cylindrical or spherical indenters are pressed onto the upper surface of the elastic layer causing a small deformation mode. Shear stresses between the indenter and the layer are assumed negligible and the layer is assumed to be either bonded or unbonded to the rigid foundation. The problem is equivalent to a mixed boundary-value problem of the theory of elasticity. Instead of using the Fredholm integral equation reported in the literature, the new approach obtained closed-form solutions through an infinite series. Convergence can be achieved using less than 10 terms of the series.

DOI： 10.1016/0021-9290(95)00120-4

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMERICAN SOCIETY TESTING AND MATERIALS  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：UNIV TOKYO PRESS  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：一般社団法人日本機械学会  

This paper presents analytical solutions to axisymmetric contact problems of two rigid spheres coated with elastic layers. The elastic layer is assumed to be either bonded or unbonded to the rigid sphere. In the analysis, dual integral equations are reduced to infinite systems of simultaneous equations using the technique of expanding the normal contact stress to an infinite series. Numerical calculations are performed for several values of the layer thickness and for several values of Poisson&#039;s ratio. These effects on the stress distribution and the external load are discussed.

DOI： 10.1299/kikaia.59.963

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

We consider an axisymmetric contact problem of a transversely isotropic layer indented by a circular rigid punch, with the elastic layer resting on a rigid foundation. This problem is equivalent to a mixed boundary-value problem in which the displacement is prescribed within the contact region of the punch and surface stresses are zero outside of the contact region. The problem is reduced to an infinite simultaneous equation using the technique of expressing the normal stress under the punch as an appropriate series. Numerical results are obtained with the indication of the effect material anisotropy and layer thickness on the stress fields in comparison with those for the isotropic material.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：UNIV TOKYO PRESS  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：一般社団法人日本機械学会  

An analytical solution is presented for an asymmetric contact problem of a transversely isotropic layer subjected to moment by a circular rigid punch, with the layer resting on a rigid foundation. In the analysis, dual integral equations are reduced to an infinite system of simultaneous equations by using the technique of expressing the normal stress under the punch as an an appropriate series. Numerical results for the contact stress and the surface displacement in three examples of transversely isotropic materials as well as in an isotropic one are presented. The effects of anisotropy and layer thickness on the stress field are discussed.

DOI： 10.1299/kikaia.57.3016

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG  

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A solution is presented for a doubly axisymmetric contact problem of the torsion in two dissimilar elastic layers by an annular rigid punch attached to its surface. The problem is solved under the assumptions that the layers are bonded together, and the other face of the layers is clamped to a rigid foundation weakened by an annular hole which is coaxial to the punch and of the same radius. The problem is reduced to infinite systems of simultaneous equations in which both the displacement on the lower face of the layers and the contact stress under the punch are expressed as an appropriate series. The disturbances due to the presence of the hole are shown in the curves calculated numerically, and the effects of various parameters on the stress field are studied.

DOI： 10.1299/kikaia.55.280

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

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A solution is presented to a three-part mixed boundary-value problem for an infinite elastic solid containing a penny-shaped crack indented by a disc-shaped rigid inclusion. The problem is reduced to a solution of infinite systems of simultaneous equations in which the normal displacement on the crack surface is expressed as appropriate series. Numerical results are given for the contact stress and the stress intensity factor at the crack tip. The effect of the inclusion on the stress field is studied.

DOI： 10.1299/kikaia.55.1215

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Authorship：Lead author   Language：Japanese   Publisher：日本機械学会  

An axisymmetric contact problem is considered to be the cause of the indentation of a penny shaped crack by a thin disc-shaped rigid inclusion in an elastic layer. This three-part mixed boundary value problem is reduced to a solution of infinite systems of simultaneous equations in which the crack shape function is expressed as an appropriate series. The normal contact stress between the inclusion and the crack surface, as well as the stress intensity factor, are shown in curves calculated numerically. The effects of various values of nondimensional parameters on the stress field and the stress intensity factors are studied.

DOI： 10.1299/kikaia.55.942

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Language：Japanese   Publisher：一般社団法人日本機械学会  

A solution is given for the frictionless indentation of a transversely isotropic layer by an annular rigid punch, where the elastic layer is resting on a rigid foundation. The problem is reduced to an infinite system of simultaneous equations using the method of expressing the normal stress under the punch as appropriate series. The effect of transverse isotropy and indentational load on the stress field are studied. Results are compared with numerical solutions for the corresponding isotropic problem.

DOI： 10.1299/kikaia.54.983

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG  

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環状孔を有する剛体床上に密着して置かれた弾性厚板の表面を円環状剛体パンチでねじる問題は二つの混合境界値問題を解くことに相当し,解析は極めて複雑になる.本研究では,厚板表面の応力と下面の変位を共に級数表示すれば,この問題は簡単が無限連立一次方程式を解く問題に帰着され,解法が簡略化されることを示した.数値計算を行って,孔のない場合の結果と比較するとともに応力場に及ぼす孔や厚板の影響等を明らかにした.

DOI： 10.1299/kikaia.52.299

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Total pages：188  

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Language：Japanese   Publisher：金原出版(株)  

＜文献概要＞本解説では,上下顎骨を撮影したコーンビームCT画像を用いてわれわれが考案した個人特有の三次元口腔内ワールド座標系に基づき,歯の形状重心から求めた三次元歯列を表現し,歯の三次元形状から主成分分析法で数学的に求めた歯の長軸方向である三次元歯軸も併せて示す新たな解析方法について述べた。はじめに,コーンビームCT画像の下顎の両側オトガイ孔2点と上顎切歯管1点を用いた解剖学的特徴点から構築した個人ごとの三次元口腔内ワールド座標系を新たに定義した。次に,正常咬合者を対象に歯列曲線や歯軸を口腔内座標系に基づいて定量的に表現した解析結果例より,上下顎歯列に対して,横断面では4次偶多項式,冠状面では6次偶多項式,矢状面では3次多項式でそれぞれの面内の歯列を数学的に表現できることを示した。

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We focus on internal stress and displacement of an elastic axisymmetric contact problem for indentation of a layer-substrate body. An elastic layer is assumed to be perfectly bonded to an elastic semi-infinite substrate. The elastic layer is smoothly indented with a flat-ended cylindrical and spherical indenter. The analytical and exact solutions were obtained by solving an infinite system of simultaneous equations using the method to express a normal contact stress at the upper surface of the elastic layer as an appropriate series. This paper presented the numerical results of internal stress and displacement distributions for hard-coating system with constant values of Poisson's ratio and the thickness of elastic layer.

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