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

BACKGROUND: Long-leg frontal radiographs of the lower extremities are used to assess knee osteoarthritis. Given the three-dimensional (3D) nature of alignment changes in osteoarthritis, postural alterations in the femur and tibia extend beyond the coronal plane (in-plane) to include the transverse and sagittal planes (out-of-plane). This study investigates the impact of these out-of-plane factors on in-plane knee alignment parameters observed in frontal radiographs. METHODS: A total of 97 osteoarthritic knees in women were examined. Using a 3D-to-two-dimensional (2D) image matching technique, we evaluated the 3D postures of the femur and tibia in the standing position as viewed from frontal radiographs in the world coordinate system. Statistical analyses were conducted to explore associations between these 3D postures and 2D alignment parameters obtained from frontal radiographs under identical conditions. FINDINGS: The femur exhibited a medial inclination of 2.7°, a posterior inclination of 3.9°, and an internal rotation of 4.2°, whereas the tibia showed a lateral inclination of 6.4°, an anterior inclination of 6.7°, and an internal rotation of 6.7°. Both coronal and rotational postures of femur and tibia influenced the hip-knee-ankle angle, mechanical axis percentage, and medial proximal tibial angle. However, only coronal factors of tibia impacted tibial joint line obliquity relative to the floor. INTERPRETATION: Attention should be paid to the potential impact of the out-of-plane postures of the femur and tibia on parameters assessed in plain frontal radiographs of the lower extremities.

DOI： 10.1016/j.clinbiomech.2024.106297

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Publishing type：Research paper (scientific journal)   Publisher：Ovid Technologies (Wolters Kluwer Health)  

Abstract

We developed two methods for three-dimensional (3D) evaluation of spinal alignment in standing position by image matching between biplanar x-ray images and 3D vertebral models. One used a Slot-Scanning 3D x-ray Imager (sterEOS) to obtain biplanar x-ray images, and the other used a conventional x-ray system and a rotating table. The 3D vertebral model was constructed from the CT scan data. The spatial position of the vertebral model was determined by minimizing the contour difference between the projected image of the model and the biplanar x-ray images. Verification experiments were conducted using a torso phantom. The relative positions of the upper vertebrae to the lowest vertebrae of the cervical, thoracic, and lumbar vertebrae were evaluated. The mean, standard deviation, and mean square error of the relative position were less than 1° and 1 mm in all cases for sterEOS. The maximum mean squared errors of the conventional x-ray system and the rotating table were 0.7° and 0.4 mm for the cervical spine, 1.0° and 1.2 mm for the thoracic spine, and 1.1° and 1.2 mm for the lumbar spine. Therefore, both methods could be useful for evaluating the spinal alignment in standing position.

DOI： 10.1097/j.pbj.0000000000000256

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Language：Japanese   Publisher：(公社)日本整形外科学会  

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

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

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Publishing type：Research paper (scientific journal)   Publisher：IOS Press  

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

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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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Other Link： https://search-tp.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2021&ichushi_jid=J05471&link_issn=&doc_id=20211007090011&doc_link_id=%2Fcx9biomc%2F2021%2F004200%2F012%2F0063-0066%26dl%3D0&url=https%3A%2F%2Fwww.medicalonline.jp%2Fjamas.php%3FGoodsID%3D%2Fcx9biomc%2F2021%2F004200%2F012%2F0063-0066%26dl%3D0&type=MedicalOnline&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00004_2.gif

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

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

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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：Elsevier BV  

DOI： 10.1016/j.jos.2021.03.009

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Language：Japanese   Publisher：金原出版(株)  

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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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PURPOSE: The purpose of this study was to three-dimensionally analyse the size and shape of the femoral posterior condyles of the normal knee. METHODS: A total of 62 healthy Japanese volunteers (37 males and 25 females) providing a sample of 124 normal knee joints, who had no knee-related symptoms and no history of major trauma, underwent computed tomography scans of the bilateral femur and tibia. Three-dimensional digital models of the femur were constructed from computed tomography data using visualisation and modelling software. The following parameters were evaluated: (1) the radii of the posterior condyles approximated to spheres and (2) the inclination angle of the posterior condyles in the coronal plane of the femoral coordinate system. RESULTS: The radii of the medial and lateral condyles approximated to spheres were 17.0 ± 1.6 and 17.1 ± 1.8 mm, respectively and were not different. The inclination angles of the medial and lateral condyles in the coronal plane were - 0.6° ± 4.6° and 9.7° ± 5.7°, respectively. The medial condyle was almost vertical, whereas the lateral one was medially tilted. CONCLUSIONS: This study found an asymmetrical inclination between medial and lateral condyles. This may be related to the asymmetrical motion of the knee, which is known as medial pivot motion. This finding provides valuable morphological information and may be useful for implant designs for total knee arthroplasty. LEVEL OF EVIDENCE: IV.

DOI： 10.1007/s00167-020-05856-2

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

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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PURPOSE: To test the hypothesis that an inclined articular surface on the medial proximal tibia is aligned more parallel to the ground in three-dimensional (3D) space under weight-bearing (WB) conditions (parallel phenomenon) than under non-WB (NWB) conditions in healthy and varus osteoarthritic knees. METHODS: We examined 55 healthy knees (26 women, 29 men; mean age, 70 ± 6 years) and 108 varus osteoarthritic knees (66 women, 16 men; mean age, 74 ± 7 years). For the evaluation under WB conditions, a 3D assessment system was used on biplanar long-leg radiographs and 3D bone models using a 3D-to-2D image registration technique. In addition, the least square method was used to determine the approximation plane. The angles between the normal vector for the approximation plane of an articular surface on the medial proximal tibia and each axis of the tibial or world coordinate system were calculated. RESULTS: Morphologically, the inclination of the approximation plane was steeper in osteoarthritic knees than in healthy knees (p < 0.0001). The approximation plane was aligned more parallel to the ground under WB conditions than under NWB conditions in healthy (p < 0.0001) and osteoarthritic knees (p < 0.0001). CONCLUSIONS: The parallel phenomenon in the medial proximal tibia was confirmed for healthy and varus osteoarthritic knees. The medial proximal tibia plays an important role in the parallel phenomenon, assumingly associated with varus alignment and varus thrust. The inclination of the medial proximal tibia may become a new parameter for imaging investigations. LEVEL OF EVIDENCE: III.

DOI： 10.1007/s00167-019-05829-0

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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: 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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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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DOI： 10.1299/jbse.19-00616

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Other Link： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2019&ichushi_jid=J05471&link_issn=&doc_id=20191009100017&doc_link_id=%2Fcx9biomc%2F2019%2F004000%2F018%2F0107-0111%26dl%3D0&url=http%3A%2F%2Fwww.medicalonline.jp%2Fjamas.php%3FGoodsID%3D%2Fcx9biomc%2F2019%2F004000%2F018%2F0107-0111%26dl%3D0&type=MedicalOnline&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00004_2.gif

Language：Japanese   Publisher：(公社)日本整形外科学会  

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DOI： 10.1007/s00586-019-06118-7

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BACKGROUND: The inclination of the medial compartment of the proximal tibia (MCT) is assumed to be a critical factor for varus alignment in advanced knee osteoarthritis (OA). This study was aimed at investigating; (1) whether the inclination of MCT is aligned parallel to the ground under weight-bearing (WB) conditions; (2) whether this is associated with the change in alignment and the relative position between the bones; and (3) whether the tibia or femur mainly contributes to the changes. METHODS: We examined 102 knees (84 women, 18 men; mean 75 years). A three-dimensional (3D) assessment system was applied on biplanar whole lower extremity radiographies using 3D-to-2D image registration technique. The evaluation parameters were 1) MCT angle, 2) femorotibial angle (FTA), 3) medial-lateral femoral location to the tibia (M-L femoral location), 4) WB line passing point, and 5) tibial position to WB line (tibial position) and 6) femoral postion to WB line (femoral position). Each parameter was evaluated in non-WB and WB conditions, and the differences (Δ-parameters). RESULTS: MCT angle in the world coordinate system was larger than that in the tibial coordinate system (p <  0.0001). ΔMCT angle was correlated with ΔFTA (p = 0.002) and ΔM-L femoral location (p = 0.004). The tibial position was the more dominant factor for ΔMCT angle (p = 0.001), ΔFTA (p <  0.0001), and ΔWB line passing point (p <  0.0001) . CONCLUSIONS: The inclination in MCT was aligned parallel to the ground under WB conditions (tibial parallel phenomenon). The parallel phenomenon was associated with the change of alignment and the relative position between the bones in the coronal plane. These phenomena were produced mainly by the tibia, not the femur. LEVEL OF EVIDENCE: Level IV.

DOI： 10.1186/s40634-019-0180-x

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Language：Japanese   Publisher：(公社)日本整形外科学会  

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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   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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DOI： 10.1371/journal.pone.0202488

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BACKGROUND: Humans support their bodies exclusively by vertical balance in bipedal locomotion, and the body, especially the lower extremity, generally changes with age. Sex and body constitution are assumed to be associated with lower extremity alignment, but this association remains to be elucidated. This study sought to clarify this association in healthy, elderly, non-obese humans in a Japanese population. METHODS: The present study investigated 55 healthy volunteers (mean age: 70 ± 6 years). A 3D extremity alignment system was applied under weight-bearing conditions on biplane long lower extremities X-rays using a 3D-to-2D image registration technique. The evaluation parameters included 3D hip-knee-ankle angle (3DHKA) alignment in the coronal (coronal alignment) and sagittal planes (sagittal alignment) and rotational alignment between the femur and tibia. The influences of sex and body constitution on all the alignment were analyzed. RESULTS: Multiple linear regression analysis with the dependent variable of each alignment showed that sex was the dominant factor for coronal and rotational alignment (coronal: p <  0.01; rotational: p <  0.01), and body weight was the dominant factor for sagittal alignment (p <  0.01). CONCLUSIONS: The association of sex with coronal and rotational alignment and of body constitution with sagittal alignment were proved in healthy, elderly, non-obese humans in a Japanese population. This finding can lead to further understanding of the etiology of many diseases and age-related changes.

DOI： 10.1186/s40634-018-0147-3

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DOI： 10.1016/j.arth.2018.02.009

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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>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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DOI： 10.1016/j.jos.2017.01.002

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DOI： 10.1007/s00167-016-4166-2

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DOI： 10.1299/jsmehs.2017.54.e043

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DOI： 10.1299/jbse.15-00364

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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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DOI： 10.1007/s00167-014-3296-7

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DOI： 10.1016/j.gaitpost.2015.04.018

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DOI： 10.1007/s00167-013-2767-6

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DOI： 10.11395/jjsem.14.s291

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DOI： 10.1299/jbse.13-00162

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DOI： 10.1007/s00167-012-2010-x

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DOI： 10.1115/1.4024284

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DOI： 10.1002/jor.22126

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DOI： 10.1007/s00776-011-0149-9

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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

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DOI： 10.1115/SBC2011-53521

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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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DOI： 10.11395/jjsem.10.s234

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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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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： 10.1007/s00776-009-1414-z

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DOI： 10.1016/j.jbiomech.2009.08.022

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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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DOI： 10.11395/jjsem.9.s167

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DOI： 10.11395/jjsem.9.s162

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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： 10.1299/jbse.4.192

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DOI： 10.11396/jjsndi.57.89

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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&amp;ndash;strain relations up to a true strain of 8% at a strain rate of 260s&lt;SUP&gt;-1&lt;/SUP&gt;. Gamma irradiation in air significantly increased the Young&#039;s modulus and the 0.5% yield stress, and gamma irradiation in N&lt;SUB&gt;2&lt;/SUB&gt; 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 Bergstr&amp;ouml;m [Biomaterials Vol.23 p.2329 (2002)]. We found that the elasto-viscoplastic model had a potential to predict the observed impact stress-strain responses.

DOI： 10.2472/jsms.57.882

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DOI： 10.11345/nctam.56.15

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DOI： 10.11345/nctam.55.61

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This study analyzed tibio-femoral joint kinematics and contact area during knee flexion at 0ｰ, 30ｰ, 60ｰ, 90ｰ and 135ｰ 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ｰ, 30ｰand 60ｰ. Sagittal and coronal images were obtained under the loading and unloading situations from 6 healthy male Japanese volunteers. At unloading situation, from 0ｰ to 90ｰ the centroids of the medial and lateral contact areas translated backward and outside. From 90ｰ to 135ｰ the centroids of the medial and lateral contact areas translated backward and inside. The contact areas tended to decrease, but from 60ｰ to 135ｰ 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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DOI： 10.11395/jjsem.6.31

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DOI： 10.11345/nctam.54.3

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DOI： 10.11395/jjsem.5.40

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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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DOI： 10.11395/jjsem2001.3.225

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DOI： 10.11395/jjsem2001.2.117

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DOI： 10.11345/nctam.50.91

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Dynamic compressive behaviour of bovine trabecular bone was investigated. Compression tests on cylindrical specimens of bovine distal femurs were carried out using the split-Hopkinson pressurebar (SHPB) technique at strain rates ranging from 100 to 700 s&lt;SUP&gt;-1&lt;/SUP&gt;. Quasi-static compression tests were also performed using an Instron-type materials testing machine at strain rates of 2&amp;times;10&lt;SUP&gt;-4&lt;/SUP&gt; and 2&amp;times;10&lt;SUP&gt;-3&lt;/SUP&gt; s&lt;SUP&gt;-1&lt;/SUP&gt;. Stiffness and ultimate strength were greater at greater apparent density and at higher strain rate. Both stress relaxation and creep functions were determined based on stress-time and strain-time relations obtained by the SHPB tests. Relaxation time and retardation time had no correlation with apparent density. The three-element standard linear solid model was then validated by these functions. The elastic spring stiffness of the model, E&lt;SUB&gt;1&lt;/SUB&gt;, had a strong positive correlation with apparent density, while the elastic spring stiffness, E&lt;SUB&gt;2&lt;/SUB&gt;, and the viscosity coefficient, &amp;eta;, showed less correlation with apparent density. No significant differences in the relaxation and retardation times, the elastic spring stiffnesses, E&lt;SUB&gt;1&lt;/SUB&gt;, E&lt;SUB&gt;2&lt;/SUB&gt;, and the viscosity coefficient, &amp;eta;, were observed between the specimens with and without marrow.

DOI： 10.1299/kikaia.63.2624

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DOI： 10.1007/BF00058972

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&lt;p&gt;Knowledge of the behavior of articular cartilage contact is one of the requirements in designing artificial joints that reproduce precise finger functions. The thumb has a different role from the other fingers, and when one of the other fingers moves, the thumb moves to the opposite position, enabling pinching and grasping, which are essential to activities of daily living (ADLs). The interphalangeal (IP), metacarpophalangeal (MCP), and trapeziometacarpal (TMC) joints give the thumb more degrees of freedom than the other fingers. The purpose of the present in vivo study was to clarify the static three-dimensional articular cartilage contact behavior of the thumb IP and MCP joints in positions of the thumb commonly used in ADLs (i.e., pinch and grasp positions) and also to analyze the changes of the articular cartilage contact area and movements three-dimensionally using magnetic resonance imaging.&lt;/p&gt;

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

&lt;p&gt;Viscoelastic models are necessary to simulate the behavior of time-dependency materials such as polymer industrial products and biological tissues. Indentation test have been widely used in the many study because of its simplicity for estimate of local mechanical properties of bulk materials. This study obtained analytical solution of relaxation indentation problem of viscoelastic thin layer bonded on rigid substrate indented by flat-ended cylindrical punch using elastic-viscoelastic corresponding principle for axisymmetric elastic contact problem. The relaxation indentation test is conducted for two different polymer materials which are polymethyl methacrylate (PMMA) and polyvinyl chloride (PVC) and bovine articular cartilage of the femoral head. For bovine articular cartilage, normal cartilage treated by collagenase after relaxation indentation test and test is conducted again. The standard linear solids model is chosen as viscoelastic model in this study, then viscoelastic parameters of the model are determined by fitting experimental data collected from the relaxation indentation test. As results, the values of Root Mean Squared Error (RMSE) which indicate the error between experimental data and analytical solution show 0.59, 0.37 for respectively PMMA, PVC and 0.78, 0.52 for respectively normal and treated bovine articular cartilage. The results indicate articular cartilage needs more complicated viscoelastic model than the standard linear solid model. The analysis provide a fundamental basis for evaluating viscoelastic parameters of thin layer with the relaxation indentation test.&lt;/p&gt;

DOI： 10.1299/jsmemm.2017.OS1102

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&lt;p&gt;Assessment of in vivo articular contact behavior at the wrist joint are important for understanding the biomechanical functions under physiological and pathological loading. The objective of this study was to evaluate in vivo articular contact behavior between the radius and scaphoid and between the radius and lunate using a two-dimensional to three-dimensional image matching technique. Two normal male subjects were enrolled in this study. Biplanar X-ray images were taken during dosal flexion/palmar flexion and ulnar/radial deviation of the wrist joint. The articular contact was estimated from the joint space distance smaller than the cartilage layer thickness measured using a MRI scanner. The distributions of estimated contact area and the contact locations varied markedly with wrist position. The present result would be able to provide a fundamental knowledge about the biomechanics of the wrist joint.&lt;/p&gt;

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

&lt;p&gt;The interphalangeal (IP) joint of the thumb are formed by the articulation between the proximal phalanges head (PPH) and the distal phalanges base (DPB). The measurement of the contact behavior, i.e., distribution and magnitude of the joint contact area with motion is necessary to understand the effects of loading on articular cartilage. The purpose of this study is to determine the in vivo contact behavior of the IP joint of thumb using the MRI. Five normal right thumbs from 5 healthy subjects were examined. Subjects were scanned with their dominant hand in three positions. Contact area was determined by measuring the length of contact between the PPH and DPB in each slice, multiplying this length by slice thickness of 1-mm, and summing these values. We found that the average cartilage contact area attains a minimum value in the neutral position. We also found that the distal phalanx of thumb IP joint was caused internal rotation on the distal phalanx with flexion.&lt;/p&gt;

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

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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&lt;p&gt;The tooth axis is important as a morphological reference axis; however, a general definition of the tooth axis has not been established. This study presented a novel method of automatically calculating three-dimensional tooth axes on in vivo Cone-Beam Computed Tomography (CBCT) images. In this study, 36 teeth were obtained from 12 central and lateral incisors, and canines of 3 human subjects, respectively. Human in vivo images were obtained using a CBCT at a spatial resolution of 0.183 mm&lt;sup&gt;3&lt;/sup&gt; . The automatically tooth axis (PC-A) was calculated using principal component (PC) analysis of the segmented tooth and mandible. In experimental results using 36 teeth, the average relative angular errors between the tooth axes T-A manually specified by three dentists and the PC-A automatically calculated by the proposed method were 2.2 ± 1.4° for central incisors, 1.7 ± 1.0° for lateral incisors, 2.3 ± 1.4° for canines, respectively. The relative distance errors between the T-A and the PC-A were 0.39 ± 0.17 mm, 0.39 ± 0.21 mm and 0.63 ± 0.34 mm for central incisors, lateral incisors and canines, respectively. The experimental results of this study demonstrate that the proposed method of CBCT can accurately and automatically identify individual three-dimensional tooth axes.&lt;/p&gt;

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

&lt;p&gt;Although the trajectories of skin markers tracked with an optical motion capture system have widely been used as the estimates of the underlying bone motions, the reliability of the kinematics parameters derived from the skin marker-based technique has often questioned due to soft tissue artefact. The objective of this study was to evaluate soft tissue artefact associated with knee flexion. One healthy female subject participated in this study. The subject underwent CT scan to reconstruct 3D femoral and tibial bone models. Twenty two polymeric markers with radio-opaque beads in its center were attached to the thigh and the shank. The initial coordinate transformation matrices were determined between skin marker cluster and the femur or the tibia using an image registration technique at extension of the knee. The movements of the femur and tibia from extension to 90° of flexion of the knee were recovered using two methods: 1) Placing the bone models according to the initial coordinate transformation matrices. 2) Placing the bone models using updated coordinate transformation matrices at every time step by a point-cluster technique. Although the latter method created more realistic bony movements especially at large knee flexion angles, a certain amount of soft tissue artefact still remained.&lt;/p&gt;

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&lt;p&gt;We consider an elastic contact problem for indentation test of layer-substrate body. An elastic layer assumed to be perfectly bonded to an elastic semi-infinite substrate. This problem called Boussinesq&#039;s problem which is axisymmetric mixed boundary value problem in elasticity theory. The elastic layer is smoothly indented by a flat-ended cylindrical and spherical indenter. The analytical solutions are obtained by solving an infinite system of simultaneous equations using the method of expressing a normal contact stress at the upper surface of the elastic layer as an appropriate series. Convergence can be achieved using less than 10 terms of the series. The accuracy of values of present numerical results is verified by comparing the dimensionless axial load of present results with results of some previous literatures. Additionally, this paper presents not only distribution of the dimensionless normal contact stress under cylindrical and spherical indenters but also distribution of the dimensionless normal displacement at the upper surface of the elastic layer. Numerical results are given for several combinations of the ratio of shear modulus, Poisson&#039;s ratio of elastic layer and substrate and the thickness of elastic layer. These results may establish the foundation for indentation test of layer-substrate composite and provide guideline for design of mechanical property of layered materials.&lt;/p&gt;

DOI： 10.1299/jsmemecj.2016.J0250301

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The proximal interphalangeal (PIP) joint of the finger are formed by the articulation between the proximal phalanges head (PPH) and the middle phalanges base (MPB). The PPH has two rounded condyles, separated by a shallow central groove. The opposing surface of the MPB has two shallow concave facets separated by a central ridge. Determination of distribution of joint contact and joint motion are necessary to understanding the progression of joint deterioration and to the design of appropriate implants for finger joint arthroplasty. Traditionally, such data have been obtained from in vitro study of cadaveric specimens. Magnetic resonance imaging (MRI) has recently been shown to be a valid method of quantifying the joint contact area, indicating the potential for in vivo assessment. In the present study, we adapted an MRI system to study the three-dimensional in vivo articular cartilage contact areas and contact distributions of the PIP joint of the index finger on adopting three flexion angles.

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

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The tooth axis is an important as a morphological reference axis; however general definition of the tooth axis has not been established. This study presented a novel method of automatically calculating three-dimensional teeth axes in micro-CT images. In this study, 20 teeth specimens were obtained from five incisors, canines, premolars and molars, respectively. X-ray images were obtained using a micro-CT scanner at a spatial resolution of 33×33×33μm^3. The tooth axis was calculated using a principal component (PC) analysis on the segmented soft pulp and dentin. The teeth axes of PC-A_+ and PC-A__ were defined as the including of the pulp and not, respectively. No significant differences were noted in the experimental results between PC-A_+ and PC-A__. In experimental results using 20 teeth, the average relative angular errors between the teeth axes T-A manually specified by five dentists and automatically calculated PC-A_+ by the proposed method were 1.14±0.11 deg for incisor, 1.74±0.74 deg for canine, 3.51±0.43 deg for premolar and 2.90±0.57 deg for molar, respectively.

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Language：Japanese   Publisher：東京 : 日本工業出版  

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I024898180

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Articular cartilage provides joints with low friction and wear resistance essential for repetitive gliding motion and shock absorption, while evenly spreading the applied load onto the underlying bone. Mechanical factors are strongly implicated in the development of osteoarthritis, although the exact mechanisms are still not known. To aid in understanding whether mechanical factors are primary or secondary in the evolution of the degeneration of joint, knowledge of the contact stress distribution on the joint surface is needed. In this study, the static stress distribution on the surface of contact of two rigid spheres coated with elastic layers is estimated utilizing a mechanical model to simulate a diarthrodial joint. The problem is equivalent to the mixed boundary-value problem of the three-dimensional theory of elasticity. The dual integral equations are reduced to infinite systems of simultaneous equations by using the technique of expanding the normal contact stress with infinite series. The exact and complete analytical solution of contact stress is obtained. Numerical results are obtained with indication of the effect of the cartilage layer thickness, elastic modulus, Poisson&#039;s ratio and joint conformity on the contact stress distribution.

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