We numerically analyzed the relationship between peristalsis and mixing of gastric contents. We constructed a numerical model for simulating gastric mixing with a realistic stomach geometry and multi-phase flow modeling. We used THINC/WLIC method to trace water-air interface, and immersed boundary method for moving wall boundary. We used the mixing parameter to quantify the gastric mixing. We changed the Reynolds number of gastric contents and inter-peristaltic distance to analyze the relationship between peristalsis and mixing of gastric contents. When the Reynolds number increase, the efficiency of gastric mixing increases. This is because the size of vortex generated behind the peristalsis increases with the Reynolds number. Flow generated by a peristalsis interacts with flow generated by next peristalsis, hence, mixing is enhanced. The cycle of peristalsis also affects mixing efficiency. When the peristalsis cycle is short and the inter-peristaltic distance is short, mixing efficiency is not enhanced because flow generated by a peristalsis does not interact.

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Nasal obstruction is a common problem in continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea and limits treatment compliance. The purpose of this study is to model the nasal airways and CPAP mask and investigate the effects of nasal obstruction on airflow parameters without CPAP using computational fluid dynamics (CFD).

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To reveal mechanism of airflow in alveolus, numerical simulation of airflow considering the expansion and contraction of acinar model was conducted using a realistic pulmonary acinus model. Pulmonary acinar model based on synchrotron micro-CT of mice. Model scale was 893 × 727 × 930 μm^3. The expansion and contraction deforming was changed sinusoidally with time as the moving boundary condition. To evaluate fluid mixing mechanism, streamline was drawn. Consequently, generation and disappearance of the vortex was observed periodically near wall surface of pulmonary acinar model.

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It is well known that beta-adrenergic agonist bronchodilators result in transient decreases in PaO2 levels in spite of bronchodilation. On the other hand, anticholinergic bronchodilators have been shown to have no effects on arterial blood gases. We hypothesized that the bronchodilation might alter oxygen transport from the trachea to alveoli, because the oxygen transport in the airway is governed by convection rather than diffusion. We constructed a 4D finite element lung model in which one subacinus (= the airspace supplied air by one last respiratory bronchiole) and its entire airway was included. Other lung regions were modeled as cubic sets whose side lengths were equal to their air-supplying bronchi. The lung model was moved during two seconds so that the air went into the lung from the tracheal upper open end at a constant flow rate at upright posture. By Solving incompressible Navier-Stokes equation and oxygen diffusion equation simultaneously, oxygen concentration distribution within the airway was computed. The small-airway dilation reduced oxygen concentration by 40% in average. Meanwhile, the large-airway dilation little changed it. This was because the air velocity at periphery was decrease by the small-airway dilatation, and oxygen transport there was performed only by diffusion. These results have indicated that the small-airway dilation itself decreases the arterial blood oxygen level.

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I have constructed a 4D finite element model of the human subacinus based on a previously published 4D alveolar model The alveolar wall contains capillary space connecting to the pulmonary arteriole and venule, and the air space is bordered by the alveolar membrane (=type I alveolar cell + capillary endothelium + liquid film) from the capillary space. The model expands and contracts according to the respiratory cycle, and the airflow goes in and out according to the regional volume change. Oxygen in the air is transported by convection of airflow and diffusion in the air space. Oxygen is further transported into the blood space by diffusion through the alveolar membrane and by convection of the blood flow. The blood flow is driven by the blood pressure at the inlet of the capillary network, that is equal to the pulmonary arteriolar pressure. All these processes are computed by the use of computational fluid dynamics in which Navier-Stokes equation and diffusion equation are directly coupled. For the simplicity, the alveolar membrane is regarded as a fluid whose velocity is always zero, and the pressure distribution in the air space is given as the boundary condition at every time step corresponding to the mesh motion. Simulated results indicated that the venular blood oxygen concentration was dependent of the effective alveolar surface area. Contrary to the conventional theory, the lower the diffusion coefficient of alveolar membrane caused little change and the thicker membrane paradoxically caused higher venular blood oxygen concentration. This simulation study will be useful for investigating respiratory pathophysiology and for developing an artificial lung.

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Fluid mechanics computation of a heart valve with an interface-tracking (moving-mesh) method was one of the classes of computations targeted in introducing the space-time (ST) interface tracking method with topology change (ST-TC). The method was introduced with finite element descritization. Now, we apply the method to isogeometric analysis (IGA) to calculate more accurate computation, and simplify the master-slave system in ST-TC method towards fluid-structure interaction (FSI) analysis.

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This study presents a computational framework to perform CT-based, personalized blood flow analysis in human left atrium (LA). Patient-specific LA geometry and function were obtained from the cardiac CT images of a patient acquired during sinus rhythm. A four-dimensional displacement vector field was estimated using a non-rigid registration method. The LA blood outflow across the mitral valve was calculated from LV volume change, and the flow field within the LA was derived from computational fluid dynamics (CFD) using the incompressible Navier-Stokes equation. The global characteristics of the LA motion and blood flow excellently agreed with clinical observations. The personalized blood flow analysis in the LA may be useful to evaluate the flow stasis associated with the risk of the intracardiac thrombosis and stroke.

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This research objective is to develop a time-dependent arterial wall modeling for arterial fluid-structure interaction. The computation has two challenges: (1) In the conventional method of representing the arterial lumen from medical images, there is no material-point correspondence between the representations for different instants during the cardiac cycle. (2) A zero-stress state (ZSS) needs to be estimated. The ZSS is related to the residual stress, which is normally acquired from cutting/opening the model, but here the only arterial-data source is medical images. Arterial lumens from medical images are shapes coming by deformation from the ZSS. Therefore, we propose a mapping method for that deformation that takes into account the physical properties of the artery, establishing the material-point correspondence needed. On the other hand, our current ZSS estimation method is only for finite element representation. Here, we extend the method to non-uniform rational B-spline (NURBS) representation to have higher continuities and convergence rates. Combining these two methods, material-point correspondence between the representations for different instants has been established.

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It is necessary to know the dynamics in vivo to predict vascular disease such as Arteriosclerosis, Aneurysm. As previous works, many researcher did FE analysis by using image based model to reproduce in vivo environment. However, Initial condition is unknown from image based model so that estimation of initial condition should be considered. A negative pressure loading analysis method to estimate zero-pressure state of vessel was developed as previous research. In this method, hypothetical material is filled inside the vessel wall to restraint buckling. Therefore, appropriate material which is able to restraint buckling although allowing wall deformation must be defined. In this study we validated this method to see the relationship of material property and wall thickness ratio. We built different wall thickness ratio models and found appropriate material for filling by compression analysis. Finally, we compared One is reproducing internal load test by filled model to see the effects of filling. The direction of how to define the material of appropriate material was shown in this research.

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Computational fluid-structure interaction (FSI) is a technique that can analyze the flow filed with the deformable channel. The methodology is an effective technique to reveal the blood flow around aortic valve with large deformation. On the other hand, the validation of the solution technique is required. In this study, the objective is developing a flow visualization system for aortic valve model with circulation circuit to validate the computational FSI technique. The aortic valve model has opening and closing function as a valve, and is fabricated from transparent silicone for visualization. The circulation circuit simulates pulsating flow and physiological pressure in a living body. The flow visualization system can measure three components of the flow velocity around the aortic valve model under the pulsating flow.

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A new method to improve the accuracy of 3D cine PC-MR (4D Flow) velocimetry using image restoration technique is proposed. The error of 4D Flow measured data is separated into the Gaussian noise part and the blur part, which consists of the two types of characteristic artifacts: "dragging velocity" and "lower velocity peak". The proposed method models the blur artifacts with a nonlinear point spread function (PSF) for the velocity images. The model parameters of the PSF are determined by inverse analysis with the results of a series of phantom study. And then the accurate velocity images can be estimated using image restoration with the PSF and in vivo measurement images. A validation result shows the volume flow rate (VFR) of the pseudo measurement data given by the PSF agrees with that of the 4D Flow measurement data well and the error is within several percent.

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Cerebral revascularization is a general surgery for vascular lesions. Operative procedures are decided based on surgeon's experience, however unpredictable complications are still a problem. The aim of our study is to predict complications before operation by identifying the mechanism of cerebral hemodynamics adaptations. It is considered that blood flow is regulated for meeting demand of tissue cells. There is a little study about the relationship between blood flow in cerebral arteries and cerebral demand. In this study, the total of flow rate in both sides internal carotid arteries and basilar artery is 'supply blood flow', and gray matter volume (V_G) and white matter volume (V_W) are multiplied by each literature cerebral blood flow (k_G, k_W) to calculate 'demand blood flow' (V_G・K_G+V_W・K_W). For 14 healthy volunteers and 2 patients (aneurysm and ischemic), the ratio of difference between demand and supply blood flow on the basis of supply values are studied. As the result, difference between supply blood flow and demand blood flow is -11.3% in healthy subjects. In a case of aneurysm, difference rate is low before and after surgery. In a case of ischemic, there is a high difference rate (59.1%). However, difference becomes lower (12.1%) by supply blood flow increase after operation. It is suggested that difference rate is available for diagnosis of ischemic.

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Off-pump CABG surgery requires high level of techniques. The surgeon must complete the anastomosis of two millimeter wide arteries within ten minutes on beating condition. Due to its difficulty, an effective training platform of DRY LAB with assessments is in strong need. This study investigated the models of anastomosis configurations and a relationship between the model and the energy loss (EL) using a beating heart simulator (BEAT, EBM) and coronary artery model (YOUCAN, EBM) which were developed from this research. The models for the analysis were chosen based on the actual EL; low (X: 42 μW), medium (Y: 196 μW) and high (Z: 362 μW) values. The effective cross-sectional areas were set by taking the cross-sectional areas from the mainstreams. The calculated EL was calculated using Hagen-Poiseuille because energy loss is inversely proportional to the square of the minimum effective cross-sectional area in a Hagen-Poiseuille flow. Results indicated that the change of the velocity distribution of the area in Y and Z were greater than those in X. The minimum effective cross-sectional areas were 2.1 mm^2 (X), 1.2 mm^2 (Y), 0.8 mm^2 (Z). Therefore, it was confirmed that mainstream could not utilize the anastomosis configuration efficiently in Y and Z. In addition, it was found that the calculated EL and the actual EL had a strong correlation, and the minimum effective cross-sectional area influenced the actual EL strongly.

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Pipeline flow diversion stent is often placed in a tortuous anatomy. Nevertheless, effect of parent artery curvature on the flow diversion effect from pipeline stent is poorly understood. We evaluated the flow diversion effect of pipeline in various parent artery curvatures and angle of incidence in in-vitro models. Four acrylic prototypes of curved tube with a side branch were constructed with circular cross section with the inner diameter of 3.8 mm. The radius of curvature R (R=25mm & 50mm), and the relative angle 0 of the side branch (θ=60, 90, & 120) were varied. The identical pipeline of diameter 4.75mm were placed to each prototype and the pressure loss occurring in the flow through the pipeline mesh was measured for the Reynolds numbers ranging from 100 to 800. The comparison with the computational study indicated that the parent artery curvature and angle of incidence are important parameters that may affect the efficacy of Pipeline.

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In order to maintain homeostasis, variety regulatory systems, including the respiration system and Autonomic Nervous System (ANS), work as negative feedbacks to adjust the cardiac output and the arterial pressure in the Cardiovascular System (CVS). In this study, we focus on the short-term regulation and aim to develop a novel mathematical model capable to evaluate the cardiovascular autonomic functions by proposing an integrative computational model of CVS and the ANS. The model is further extended to include the exercise-related regulatory mechanisms such as muscle pump function, resetting of the operating point of baroreflex regulations and central command. For simulation validation, the model is used to predict the hemodynamic response to the one-leg cycling. For further clinical application, moderate one-leg exercise in both health subjects and patients with the dilated cardiomyopathy are carried out to investigate the cardiac performance. For this purpose the comparison of the heart rate (HR) and mean blood pressure (MBP) between the health subjects and the patients with the dilated cardiomyopathy are presented in this study. In the health subjects during the moderate one-leg exercise, both the HR and the blood pressure are increased; however there is a slight decreasing in the blood pressure soon after the onset of the exercise due to the mechano- and metabo- vasodilation. On the other hand, the HR in the patients with the dilated cardiomyopathy is higher than that in the health subjects, while the difference of the HR during rest and one-leg exercise decreases. Meanwhile, the MBP in the patients with the dilated cardiomyopathy is lower than that in the health subjects, so is the difference of the MBP during rest and one-leg exercise. Furthermore all the results show reasonable agreement with experimental data and this study provides valuable information on the dynamic regulation in CVS by coupling with ANS in the clinical field.

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Watanabe et al. experimentally indicated that acupuncture stimulation to Taichong (LR-3) induced increase in blood flow volume in right brachial artery and decrease in systemic vascular resistance index, and suggested that they were induced by vasodilation of peripheral vascular resistance (PVR) of the arm. In the previous study, the authors presented a lumped-parameter approximation model of blood flow in the systemic arteries and reproduced the hemodynamic change by regulating PVR of the right arm. It is expected, however, that stimulation of LR-3 enhances blood flow volume of bilateral arms identically, though no report in literature has measured hemodynamics in bilateral arms, because this acupoint is to ameliorate limb chills. In the present study, the authors examined to reproduce the hemodynamic change by regulating PVRs of bilateral arms, assuming those PVRs would be changed identically by the stimulation. Thorough this study, it was indicated that the stimulation of LR-3 causes greater decrease in the blood flow volume of other arteries than the arms in compensation for increase in the blood flow volume in the arms, comparing the previous study.

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Fontan procedure is a surgical palliation used to treat patients with congenital heart disease such as single ventricle. Fenestration, a small hole between the conduit and right atrium, is expected to reduce the postoperative morbidity. Several recent studies have reported its effectiveness and favorable shapes. However, there is still no evidence on how the fenestration location influences three-dimensional hemodynamics in Fontan procedure. In this study, we constructed a three-dimensional patient specific model with fenestration based on the medical images. The three-dimensional blood flow in Fontan Circulation is treated as laminar flow and computed by solving the Navier-Stokes equations; boundary conditions with the influence of respiration are imposed at inlets and outlets. Our results indicate that locating the Fenestration in the middle of extra-cardiac conduit is the most effective way in terms of cardiac outputs and pressures.

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Femoral neck fracture is one of serious healthcare problems in aging societies. Osteosynthesis with implants is widely used for femoral neck fracture treatment, however, complications such as bone refracture around implant insertion holes may occur during postoperative rehabilitation period. Authors had already numerically analyzed osteosynthesis with implant under a static loading condition. In order to resolve the mechanics of the complications, we should analyze under the dynamic loading condition corresponding to gait motion. The purpose of this study is to evaluate not only time dependent stress distribution but also maximum stress concentration around proximal femur by using finite element analysis under the dynamic loading condition. First, three-dimensional hip joint finite element model was reconstructed from CT image. This model consists of the pelvis, proximal femur and implants (Hansson pin and Dual SC Screw). Then, dynamic loading and boundary conditions were applied to the model for simulating a gait motion. The dynamic loading around the hip joint was obtained from inverse dynamic analysis of a human gait using in-house musculoskeletal model Time varying stress distribution during a gait cycle was analyzed by using dynamic explicit method (AB AQUS ver.6.13-5). We examined the time varying von Mises stress distribution at the representative points located on the cortical surface. These simulation results successfully demonstrated the excessive stress concentration around the insertion holes induced by the gait motion. It is proofed that the proposed dynamic analysis has the capability of the refracture risk assessment of the osteosynthesis of femoral neck fractures.

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The acetabular dysplasia is pathological condition that acetabulum is incomplete growth compared to healthy people. In everyday life movement of the hip joint is indispensable and life while always felt the pain and discomfort is significant failure. Further, by that operation to protect the hip by pain, which can cause a secondary disability. A variety of treatments exist for acetabular dysplasia. The acetabular shelf arthroplasty is also one of them. It is a surgery to increase the load area transplanted with autologous bone. It has feature that is excellent in improving postoperative pain. In this study, we constructed a novel three-dimensional trunk musculoskeletal model using data from computed tomography (CT) and magnetic resonance imaging (MRI). Using it was estimated joint force of the hip of a subject. And subjected to acetabular shelf arthroplasty in a patient with acetabular dysplasia, create a 3D model from CT images of postoperative preoperative, subjected to mechanical evaluation by using the finite element method. As a result, the variance of the stress in the hip joint surface has been confirmed. It can be said that the acetabular shelf arthroplasty is an effective means for acetabular dysplasia.

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It is considered that foot plays an important role in shock absorbing and stability maintaining during various motions including walking, running and so on using the complex structural mechanism. It is critical issue for many rehabilitation professionals and robotics engineers to find out the mechanism of the function of foot exerted based on the complex structure which consists of bones, ligaments, articular cartilage, muscles, fat, and others. The aim of this work is to reveal the effects of the passive hindfoot motion on the ankle moment during stance phase using a computer model of the foot and ankle complex. We obtained the geometrical model of bones and cartilages from MRI and the morphology of ligaments and plantar fascia by anatomy data from literatures. It was found that passive ankle joint resistance moment increases when the anterior motion of talus induced by ground reaction force. However, limitations remained includes that the boundary condition and constraint condition are slightly different from real gait so that it is considered the passive ankle moment is estimated higher value potentially.

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Pelvic floor disorder, which is a well-known urological disease in postpartum women, progresses due to dropping organs in the pelvis. It was reported that symptoms of pelvic floor disorder had been improved by lifting up the organs using a supportive underwear. In order to establish an appropriate design of a supportive underwear, it is necessary to clarify the relationship of magnitude between pressure of a supportive underwear and elevation of organs. FE model of buttocks was previously developed by image-based modeling technique based on MRI pictures to evaluate the magnitude of elevation of bladder under an application of pressure of an underwear. In this study, we performed FE analysis changing combination of pressure of the underwear to evaluate change in magnitude of elevation of the bladder neck. As results, magnitude of the elevation of bladder neck relatively increased when the pressure of the region from abdomen to pubis decreased and the region from perineum to coccyx increased. Additionally, deformation of the bladder neck was consistent between the simulation results and the previous experimental results, suggesting that our simulation method was valid. Therefore, decrease of the pressure of the region from abdomen to pubis and increasing the pressure of the region from perineum to coccyx are useful for an appropriate design of a supportive underwear.

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The sterEOS X-ray machine is capable of a simultaneous capture of biplanar X-ray images by slot scanning of the whole body in physiological load-bearing position. The simultaneous capture of spatially calibrated anteroposterior and lateral images provides a three-dimensional (3D) surface modelling of the skeletal system using sterEOS 3D software. The relevant clinical parameter such as spinal and vertebral parameters are supposed to be measured. The aim of this study is to evaluate an accuracy of EOS measurement of spinal alignment. A phantom for X-ray imaging was used for CT scanning and sterEOS X-ray imaging. 3D surface models of a phantom were reconstructed from its CT images. The same clinical parameters measured from CT-derived 3D surface models and sterEOS 3D software were compared.

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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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In recently years, aging of the population progresses in our country. These problems are not only increasing of elderly population, but also a factor of increasing burden of carer. We must correct these problems. Thus, we have developed High Valued Walking Training System. The purpose is aimed independence support people and burden reduction of the elderly. This system is constructed with a walking assist device using pneumatic artificial muscles, high-performance Shoes detecting sole load and an active walker resorbing shock. Specifically, by walking assist device and high-performance shoes, while presenting a walking state in the subject, to carry out the support of the walking motion. And by using the active walker simultaneously, we can do walking training for safety. Further, by using the system, we prompt elderly people to become independent and decrees burden of care takers. In this paper, we clear basic characteristics of rubber artificial muscle actuators for high valued walking training system.

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This paper presents a system for evaluating balance in elderly people to prevent fells. The proposed system comprises a position sensor for measuring the upper body joint position, a stabilometer for measuring the center of pressure trajectory and the seat reaction force, a one-degree-of-freedom platform for producing seat perturbation. The seat reaction force and joint position of the upper body were used to calculate the joint torque of the 3rd lumbar vertebra. In addition, electromyography was measured a line call of the young to watch the function of human of trunk line at the time of the unrest. In the experiments, 29 young and 17 older healthy adults tried to maintain a sitting posture relative to the seat perturbation (0.3 Hz 7 deg amplitude). The root mean square of COP trajectory and the joint torque of the 3rd lumber vertebra in elderly people were significantly higher than those in young subjects. Line activity for the unrest was seen with almost all human trunk lines of the young. Results of experiments show that the COP trajectory and the joint torque were significantly higher in elderly subjects.

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The FES cycling of rehabilitation apparatus using functional electrical stimulation is generally metabolic efficiency is low. In this research, measured the metabolic efficiency from oxygen consumption and mechanical work at the time of movement by the FES cycling intended for able-bodied people and compared the metabolic efficiency of the exercise by the voluntary cycling exercise and FES cycling. The result, in the exercise by the FES intended for able-bodied person, was small result of the change in oxygen consumption and carbon dioxide emissions are obtained. Therefore, it is clearly that require clinical metabolic efficiency experiments intended for lower limb disabled persons.

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In order to evaluate the joint moment of cycling motion using FES cycling (Functional Electrical stimulation cycling for people with disabilities), The authors developed three kind of FES cycling with various BB (Bottom blacket) height (low, middle, high). In this study, the effect of riding position (BB height) on the joint moments of lower limb were evaluated for eble-bodied person with and without FES by using 6 axis force sensor and 3D motion analysis setup. As a first step, the authors perform the experiment for middle BB height, able-bodied person without FES in the case that additional load (25W) condition and no-load condition.

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A slot-scan digital radiography (SSDR) 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 small image distortion compared with conventional x-ray systems. The purpose of this study was to develop a method for evaluation of the three-dimensional (3D) alignment of the lower extremity using a biplanar SSDR system and bone surface models. The biplanar SSDR 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. Sawbone femur and tibia were used to replicate the alignment of lower extremity. Three acrylic markers were attached to each sawbone to define the local coordinate system Computed tomography of the sawbone femur and tibia was performed to allow the reconstruction of the 3D surface models. Then the femur and tibia were fixed at three different alignments of the knee; extension, axial rotation, and varus deformity. For each alignment the femur and tibia were imaged using the biplanar SSDR system. The 3D positions of the femur and tibia were recovered using an interactive 2D to 3D image registration method. Overall, the largest estimation errors were 1.1 mm in translation and 0.9 deg in rotation, demonstrating that this method has an adequate accuracy for the clinical usage.

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Many of the elderly are predisposed to develop osteoarthritis (OA), although it is quite difficult to diagnose the early-grade OA even by latest imaging modalities. The purpose of this study is the clinical development of D-OCSA arthroscopic system. The visualization system using Arthroscopic Optical Coherence Tomography (OCT) probe which is essential as a diagnostic system has been developed. In addition, ex vivo animal experiments applying D-OCSA were also carried out using rabbit's OA cartilage caused by amputation of the rabbit's left knee ACL. As an experimental result of Arthroscopic OCT probe, it was confirmed that the construed system could provide morphologic diagnosis of cartilage, e.g. tide mark. D-OCSA can show the attenuation coefficient distribution of compressive strain rate during relaxation test, which could find superior increase in attenuation only for early OA cartilage. Therefore, it can be seen that there is a loss of visco-elastic properties as compared to normal cartilage. In summary, Arthroscopic D-OCSA system could be effective to assessments of the early OA as "Micro Mechanical Biopsy".

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The objective of this study was to clarify the contribution of the anterior cruciate ligament (ACL) on the knee joint stability. The ACL consists of three ligament bundles, each with their own different function. Based on the ACL triple bundle theory, a porcine stifle joint with the anteromedial bundle (AMB), intermediate bundle (1MB) and posteromedial bundle (PLB) was prepared. The knee joint was placed in a material testing machine capable of releasing/constraining 5 DoFs of the knee. The load contribution of each bundle was estimated by, sequentially cutting each bundle from the knee joint and measuring the load during an anterior-posterior drawer test. As a result, large decrease in the load contribution was observed when 1MB and PLB were cut, however only a small contribution was seen for the AMB.

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Quantitative biomechanical data on the deformation behavior of the anterior cruciate ligament (ACL) under knee loads are necessary for a better understanding of ACL functions, prevention of injuries, and improvement of ACL reconstruction. The objective of the present study was to apply both robotic system and motion tracking system to the determination of site-dependent, 3-dimensional strain in the ACL, specifically focusing on the attachment area to the femur and tibia, during anterior translation of the knee. Porcine knee joints (n=5) were dissected down to the joint capsule and fixed to the robotic system. The anterior drawer test was performed up to 50 N at full extension. After the lateral condyle was removed for the observation of the ACL, the intact knee motions were reproduced. The medial view of the ACL surface during the test was recorded with a CCD camera. Using a motion tracking system (VW-9000, KEYENCE, Osaka, Japan), the surface deformation of the ACL including the attachment areas to the femur and tibia was analyzed. Measurement was performed not only for the surface layer, but also in the middle and deep layers. Results revealed that strains in the ACL attachments were larger than those in the middle portion in all layers. Moreover, a dramatic change in crimp pattern was observed in the attachment areas of the ACL in response to tensile force. The present result suggests that the local strain in the attachments area is complicated and site-dependent in porcine knees.

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Presentation of various softness feeling of complicated multilayer anatomical structures has been required for the medical robots. Because the relationship between psychological and physical multilayer softness has not been clarified. In this study, the threshold of psychological and physical multilayer softness was investigated by focusing on both the psychological engineering approaches and the physical Young's modulus of multilayer. 10 subjects' fingers touched to both 2.5% and 5.0% concentration single-layer gelatin jellies and touched to 5 double layer gelatin jellies of which all of upper layer was 2.5% jelly, and lower layer were 5.0%, 7.5%, 10.0%, 12.5%, and 15.0% jellies, respectively in this experiment. After that, subjects evaluated 5 items of multilayer softness. The results showed that number of subjects felt to be multilayer was 5 out of 10 subjects at lower 10.0% jelly layer, the number was 8 at lower 12.5% jelly layer, and the number was 10 at lower 15.0% jelly layer. Therefore, the threshold of psychological multilayer softness existed between lower 10.0% and 12.5% jellies layer. When the upper layer of the Young's modulus was 0.00518 N/mm^2, the physical Young's modulus threshold of lower layer existed between 0.0573 and 0.0981N/mm^2.

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Microscopic structure of articular cartilage, including collagen and proteoglycans, is believed to provide a major impact on the low-friction functionality of the joint. Osteoarthritis is degenerative joint disease and might reduce joint function. The method to evaluate the function of knee joint is required for the use of treatment. Pendulum test method is one of the way to assess mechanical characteristics including coefficient of friction. In this study, the pendulum tests of rabbit knee joints were conducted by using a lightweight pendulum frame (about 200g), since using heavy pendulum frame may cause damage to cartilage. Not only friction coefficient but also viscosity coefficient and elastic coefficient were calculated from the pendulum decay curve. Pendulum tests with various pendulum masses and positions of gravity center were carried out by attaching the weight on the frame. Friction coefficient and viscosity coefficient tended to increase with increasing the weight of pendulum. Moreover, a tendency that the friction coefficient and viscosity coefficient increases were observed as the gravity center of pendulum lowered.

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Visco-elastic properties of skin tissue is strongly dependent on moisture content around epidermal tissue, which should cause skin wrinkles Therefore, an in vivo quantitative measurement of moisture content is necessary to clarify skin mechanics. In this paper, we propose OCM (Optical Coherence Moisturegraphy), which is a method of tomographic micro-visualizing moisture content using low coherence interferometer with 1400 nm band light source. The tomographic detection of the intensity attenuation due to light absorption of water can determine moisture content profile inside skin tissue. The rapid scanning optical delay line was implemented as a reference arm so as to visualize video-rate tomography of moisture content field. In order to verify the proposed system, respective OCT system with 1300 nm and 1400 nm light source were applied separately to a pig skin tissue covered with a moisturizing sheet. Consequently, the interference signal intensity of 1400 nm band, comparing with 1300 nm band, was observed tomograpically to be decreasing exponentially with water diffusion inside skin. It was concluded that OCM has promising potential of diagnosing tomographic moisture content inside skin tissue.

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Since lymph node metastasis is a major prognostic factor of cancer, the development of early diagnosis system for lymph node metastasis is essential for improving the outcome of cancer treatment. It has been reported that metastatic cancer cells promote lymphngiogenesis. In this study, to test whether detection of lymphangiogenesis in the metastatic lymph node is a useful maker for diagnosis of lymph node metastasis, we analyzed contrast micro-CT imaging of lymphatic vessels in the metastatic lymph node of animal model for lymph node metastasis. The animal model used here was MXH10/Mo-lpr/lpr mice whose lymph nodes are enlarged to 10 mm in diameter. As a results of this study, the missing region of the contrast effect was observed in the contrast micro-CT imaging of the early metastatic lymph node.

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Endolymphatic hydrops is a disorder of inner ear and is associated with abnormal fluctuations in the endolymph fluid. These fluctuations cause an increase of pressure in scala media of the cochlea. The symptoms of endolymphatic hydrops include hearing loss especially at low frequencies and balance problems. To investigate the reason of hearing loss at low frequencies, we aim to analyze endolymphatic hydrops with the finite element cochlear model which is considered activity of outer hair cells. At first, we developed models of endolymphatic hydrops by loading static pressure in scala media. Each pressure of model is 10, 100, 500 Pa. Next, we analyzed the normal cochlear model and the endolymphatic models with loading sound pressure at frequency of 125 Hz to 2 kHz. As the results, the displacement of the basilar membrane of the endolymphatic hydrops model was smaller than the numerical result obtained from the normal cochlear model at low frequencies under 500 Hz. Also, characteristic frequency of the endolymphatic model was not matched with characteristic frequency of the normal cochlear model at low frequencies. These results show that increase of pressure in scala media might cause hearing loss at low frequencies.

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In our previous research, a new subcutaneously implanted bone conduction hearing aid has been proposed. The hearing aid is composed of an external unit and an internal unit. The external unit consists of a microphone, a sound processor and a transmitting coil. The internal unit consists of a receiving coil, a driving coil, a demodulator and a vibrator. The vibrator is made of giant magnetostrictive material (GMM) which deforms its length in response to change of surrounding magnetic field. The internal unit is embedded under the skin and vibrates the temporal bone when the magnetic flux is supplied by the external unit. Our research group has studied to improve the transmission efficiency between the transmitting coil and the receiving coil by adopting the amplitude-modulated (AM) signal with high frequency carrier wave and the magnetic resonance coupling. However, the driving characteristic of the vibrator has not been investigated when AM wave was input. In this study, the optimal driving method for the vibrator was examined by measuring the amplitude and the harmonic distortion of the vibrator when AM waves were input. The vibrator has a linear response in proportion to the current of AM wave when modulation factor is fixed. However, harmonic distortion of the vibrator is increased when the current of AM wave is small. The AM wave having modulation factor of 50 % can suppress harmonic distortion. To consider the threshold value of the current required for the hearing aid is an issue in the future.

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The ossicular chain, which consists of the malleus, the incus and the stapes, plays an important role in auditory mechanics. If the ossicles become fixed somewhere, hearing loss occurs. In order to improve the level of hearing, the fixed part of the ossicles must be replaced. It is important to evaluate the mobility of the stapes during the tympanoplasty surgery, because the ossicular mobility affects the prognosis for the improvement of the hearing level. However, an objective measurement of the stapes mobility has up to now been rarely performed during a surgery. In a previous study, we created a mechanism which consists of a force sensor and an actuator and pushes the ossicles during surgery. Then we evaluated the ossicular mobility based on the relationship between the force and the displacement. In this study, we propose a new mechanism. The probe of the measuring system consists of an ear-pick, an actuator with a strain gauge and a force sensor. We vibrate the ossicles with the ear-pick and measure the reaction force and displacement of the ossicles with the force sensor and the strain gauge. From the relationship between the reaction force and the displacement, the degree of the fixation of the ossicles is quantitatively evaluated.

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A Sweep Frequency Impedance (SFI) meter, which measures the dynamic behavior of the middle ear by sweeping frequency tones from 100 to 2000 Hz, was recently developed to screen for neonatal middle-ear diseases (Wada et al., 1998, Murakoshi et al., 2013 and Aithal et al., 2014). In recent SFI measurements in neonates, two resonances at approximately 0.5 and 1.0 kHz were observed. In addition, only the lower resonance frequency moved to higher frequencies with an increase in age, finally fading out by 5 months, while no significant differences were found in the higher resonance during the 5-month test period. Our working hypothesis is that the lower resonance frequency may be related to the soft wall surrounding the ear canal, the maturation of which causes changes and subsequent fade-out of the resonance frequency. We evaluated this hypothesis by comparing SFI results with simulation results using the recently reported Finite Element (FE) modeling approach for neonates (Hamanishi et al., 2015). Simulated SPL curves were obtained by applying a constant volume displacement equivalent of 80 dB SPL at the ear canal entrance. Then, SPL curves resulting from changes in the Young's modulus of soft tissue of the ear canal (Eec) were compared. The lower resonance frequencies at 1 and 5 months after birth in SFI tests were consistent with those in FE simulations with Eec of 30 kPa and 5 MPa, respectively. Therefore, the canal wall of neonates initially consists of soft tissue, followed by rapid formation of a bony portion.

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Transcranical magnetic stimulation (TMS) mapping is a valuable tool to investigate cortical representations. Recently, a time saving method that gives stimulations at randomly selected points around a hotspot has been proposed In order to accomplish TMS mapping effectively, we here utilize center of gravity (COG) as a new indicator of random mapping instead of hotspot, to gain an accurate map in short time. Six healthy subjects participated in this study and we examined two types of mapping method that was mapped without COG navigation and with COG navigation The data set were randomly extracted one by one from the 100th, minus the outlier stimuli, to the 20th stimuli and the correlation coefficient was calculated and compared to the original mapped data. In our results, there were no significant differences between with COG NAVI and without COG NAVI in all compared data sets. However, with COG NAVI tended to show greater reliability after 40 points. In conclusion, we can define COG as the new indicator of TMS mapping. Therefore, we could offer the possibility of saving time during hotspot determination and making it possible to get a map easily without skills.

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In this study, we analyze mechanical states of TEA (total elbow arthroplasty) implant and its surrounding tissues under several mechanical conditions, and evaluate the effect of the mechanical conditions. We use two types of models for performing the analysis. One is a musculoskeletal model with AnyBody which simulates muscle forces and reaction forces. The other is a finite element model (FE model) which uses the muscle forces and the reaction forces as boundary conditions. Analysis results with a simple FE model suggested that the artificial elbow joint does not damage ulnar bone when a subject holds less than 1kg load. For patient-specific simulation, we made a study of an individual FE models based on CT images of patients. We tried to estimate a mechanical state of ulnar bone with screw insertion which fixes a coronoid fracture for application of the modeling method. We will also apply the method to analysis for TEA.

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Scoliosis is characterized by a lateral curvature of the spine with a Cobb angle of more than 10 degrees and vertebral rotation. Curves larger than 50 degrees are associated with a high risk of continued worsening throughout adulthood and thus usually indicate the need for surgery. The operation for scoliosis, called as a spinal fixation, uses modern instrumentation systems and pedicle screws are applied to the spine to anchor long rods. Here, there are a few cases that the spine get broken because of excessive loads applied to the screws. In order to avoid such situations, this study aims to find more secure surgical operation method using a powerful method of computational biomechanics, finite element analysis. This paper discusses the analytical results using simple vertebral models with two loading conditions. The main results are follows: (1) the amount of load applied to the screw and the maximum stresses or deformations have liner relationships, (2) shorter screws tend to cause higher stresses in vertebrae.

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The cementless cup shape with a fin to the cup outer circumference I've been mainly used. In recent years, cementless cup with a coarser 3D porous shaped cup surfaces are sold, improvement of initial fixation of the surface roughness in addition to the secondary fixation is also expected, but the effect is apparent sounding not. The purpose of this study is to clarify the effect of bringing the surface shape in the initial rotation fixation. The cup of three different surface shapes it was included. Using a digital torque tester measures the torque of the simulated bone and the cup, and were compared statistically. Normal model F group, the P group was significantly higher both for the N group. Group F against P group and the N group in acetabular dysplasia model but was a significantly higher, P group was almost the same as N group. Conclusion In the surface shape of the cementless cup, fin effect was observed in the acquisition of rotation fixed resistance in acetabular dysplasia model

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Femoral bone fracture pattern has simple fracture and compound fracture, and orthopaedic surgeons generally suggest medical treatments proper for fracture characteristics to the patients. For example, to fix with an intramedullary fixation nail system in the bone marrow cavity, or fix with bone fixation metal plate and screw on the fracture surface. In case of senior patients or osteoporosis patients, however, secondary fractures may occur according to the bone conditions. This study acquired anthropometrical information on femoral bones utilizing CT images of 10 Korean cadavers, and developed femur fracture fixation plate made of shape memory alloy. Also, this study simulated dynamic behaviors of shape memory alloy plate by finite element method, and analyzed contact pressure between the femoral bone and the plate models. To verify the behavior of the shape memory alloy, total deformation of the plate made of shape memory alloy was reviewed by checking the shape recovery pattern due to body temperature. According to the contact simulation between the plate and the bone, the maximum Von-Mises stress value was 10.5MPa in 2t, and 11.6MPa in 2.2t, and 13.1 MPa in 2.4t, respectively. Contact stress between the plate and the bone became higher when the plate thickness became thicker, however it was confirmed that the contact stress levels were not so high enough to burden the bone when considering yield strength of femoral bone, 108MPa.

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Some retrieval studies reveal the ultrahigh molecular weight polyethylene (UHMWPE) deformation or severe failure of the tibial post of a posterior-stabilized (PS) knee. Strength of the tibial post of available design is obviously insufficient to prevent the severe deformation. Minimally required size of the post should be clarified for polyethylene inserts. In the present study, we performed finite element analysis assumed the mechanical conditions of a tibial post in a PS knee and aimed to design criterion of a post of polyethylene insert of a knee prosthesis. The shape of three commercially available knee prostheses was referred as PS knee prosthesis. Three dimensional finite elements were generated by modeling software as four-node tetrahedral elements. A 500N posterior load was applied to each femoral component at 10 degree hyperextension, and a 1000N anterior load was applied to each femoral component at 120 degree flexion after the tibial insert had been internally rotated 10 degrees. The distributed values of von Mises stress and plastic strain on the tibial post were shown as the results of the analysis. The stress of a smaller post was higher than yield stress of UHMWPE and the strain was obviously higher than that of other posts. Our results showed that plastic deformation may occur in the posterior aspect of a tibial post by impingement during common exercises like climbing up, or squatting. The design criterion including the post size must be revised the safety coefficient which realizes that the generated stress in the tibial post is sufficiently lower than the yield stress of UHMWPE.

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Internal fixation is important for the surgical treatment of ankle lateral malleolus fracture because the fracture may cause secondary osteoarthritis in the case of residual dislocation. There are various different methods using a fixation plate, for example, a locking plate, a non-locking plate and a non-locking plate with a hook. Although a clinical study reported that a hook was useful in comminuted fracture, it is unknown whether fixed strength increases by the use of a hook. In this study, in order to determine the stability of fixation achieved with a non-locking plate with a hook, we experimentally compared it with other characteristically different means of internal fixation. Failure load, compressive stiffness and torsional stiffness were compared among the three kinds of internal fixation for a mock fracture with or without a hook and a locking plate were similar. It was suggested that non-locking plate fixation with a hook should be limitedly indicated for the surgical treatment of ankle lateral malleolus in cares of comminuted fracture or osteoporotic fracture.

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Ultra-high molecular weight polyethylene (UHMWPE), used as a bearing surface of artificial joints, has been reported to absorb lipids such as squalene (SQ) and cholesterol ester, during the service in vivo. In vitro studies using SQ as a model lipid, have suggested that lipids have potential to induce degradation of the polymer. In this study, lipid-induced degradation was simulated by SQ absorption and subsequent accelerated aging, and its effects on the durability of UHMWPE were investigated using three test methods, namely, wear, delamination and fatigue crack growth tests. Lipid-induced degradation was found to increase wear rate of both non-crosslinked and crosslinked UHMWPE by a factor of 2.6 and 11, respectively. On the other hand, lipid-induced degradation was found to have little effects on delamination resistance and fatigue crack growth rates. These results were consistent with the fact that lipid-induced degradation was localized near the surfaces reported previously. In conclusion, these results show that lipid-induced degradation could have potential to affect durability and long-term clinical outcome of artificial joints due to increased wear of UHMWPE.

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This study aims at revealing the effects of wear/ delamination of HAp coating on the surfaces of acetabular cups on loosening behaviors of the acetabular cups during cyclic loading. Loosening behaviors of acetabular cups are caused by osteolysis or aseptic loosening. However, a physical mechanism of aseptic loosening has not been clarified yet. A cyclic loading system for artificial acetabular cups with stems was facilitated. Wear/ delamination behaviors of plasma-sprayed coating on the surface of the acetabular cups were indirectly observed by AE measurement. AE measurements revealed that wear/delamination of HAp coating started from the edge of acetabular cup where concentration of shear stress occurred and propagated to the center region of the cup. Loosening behaviour of the acetabular cup was promoted by cyclic loading for both positions and fixation angles. Extents of changes in positions were larger than the critical value for deteriorating good fixation between human bone with artificial joints. Consequently, loosening behaviours due to fracture of bonding between simulated bones- HAp coating- titanium substrates were successfully observed.

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Because elastic modulus is greatly different, as for many artificial joints using metal materials, mechanical mismatch occurs between bone. Therefore we aim at the realization of the artificial joint material having mechanical characteristics of the bone to solve the mechanical mismatch between bone and the artificial joint. In this report as the basic research, we examined the compression characteristic of titanium alloy-resin composite with the macro-heterostructure to suggest as an artificial joint material. The macro-heterostructure of the specimen was obtained by topological optimization based on the finite element analysis. We aimed at the optimization so that three axial elastic property of the cube specimen was different. The shape data of the macroheterostructure obtained by structure optimization is converted it into 3D-CAD data and molded three dimensions. The molding laminated powder of the titanium alloy (Ti-6Al-4V) in electron beam. The specimen poured epoxy resin into porous material of the titanium alloy and made it decrypted. We performed a simple uniaxial compression test using the specimen. The tendency of load-stroke curve scarcely changed in each axis of X, Y and Z direction. The elastic modulus calculated by face to measure strain was greatly different in the compression of the same axial direction.

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Articular cartilage plays an important role to realize low friction coefficient in wide operating condition. While there exists several frictional mode to adapt each condition, the role of the biphasic lubrication mode relatively arises in a low sliding speed condition, where the fluid film lubrication mode can not work enough. The PVA hydrogel is expected as an artificial cartilage material, which can contain plenty of water to activate the biphasic lubrication mode. In articular cartilage, the soft gel matrix is reinforced by collagen network structure to resist tensile deformation, in which the tensile stiffness of the biphasic material generates the interstitial fluid pressurization. Higher fluid load support leads lower friction coefficient because the solid-to-solid contact pressure decreases by the increased fluid pressure. In this study, we developed the fiber reinforced PVA hydrogel to enhance the fluid pressure, which can support a considerable proportion of the contact pressure as a load bearing system. The biphasic finite element analysis showed the effective enhancement of the interstitial fluid pressurization in the fiber reinforced PVA hydrogel. The fiber reinforcement maintained the fluid load support in a migrating reciprocal sliding condition. The potential of the biomimetic artificial cartilage was expected as a load bearing material.

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