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Intervertebral disc (IVD) degeneration is associated with changes in the major biomolecular components in the disc as well as changes in enzymatic activity in the IVD. Collagen, elastin, and proteoglycans in the disc are primarily responsible for mechanical and structural support as well as disc recovery after loading. In order to investigate the effects of the loss of these biomolecules, a single...
Alterations in the major biochemical constituents of intervertebral discs coincide with aging and degeneration, and can alter the disc's ability to support load. The most significant biochemical change that occurs in degeneration is the loss of proteoglycans in the nucleus pulposus. During a diurnal cycle, the disc experiences approximately 16 hours of functional loading, followed by 8 hours of recovery...
The goal of the present work was to develop a framework for the analysis of time-varying mitral valve (MV) geometry from cardiac magnetic resonance (CMR) imaging, and to integrate these data in a patient-specific simulation of MV closure. CMR imaging of 18 long-axis planes was performed on a healthy subject and on two ischemic patients with MV regurgitation. MV annulus geometry, leaflets surface and...
The aim of our study was to develop a 3D model for myocardial wall stress (MWS) evaluation and to test its ability to characterize left ventricular (LV) aging and the effect of aortic valve stenosis (AVS). We studied 65 subjects (45 controls and 20 with AVS) who had a cardiac magnetic resonance (CMR) exam and a measure of central pressures. 3D MWS evaluation combined systolic pressures and an LV geometrical...
Determining the stiffness (or compliance) of biological vascular vessels is of importance when investigating pathological conditions, the design of stents, vascular grafts, distal anastomotic connectors in coronary artery bypass surgery, and understanding of biological pressure sensors. This communication is concerned with determining appropriate values of the material constants associated with a...
The artificial prosthesises currently used are only different in the femoral head size, neck length and stem thickness, but there is not any individualized prosthesis. At present, prosthesis looseness is the main problem of artificial femoral replacement, and individual matching level of joints is the bottleneck of restricting prosthesis replacement surgery. If we can design and produce corresponding...
Lachman test is a manual test for examining the anterior cruciate ligament (ACL). An examiner examines the ACL by feeling finger stress. Some measurement device for Lachman test have been developed. However, they aim to analyze not the stress but a motion of the knee joint. Therefore, we set the goal of this study to develop a measurement system for finger stress with force sensor during Lachman test...
The acetabular cartilage is normally represented as a spherical shape in orthopedic clinic and related researches. The aim of the study was to present a new mathematic representation with better fit to the acetabular cartilage surface and to investigate the role of its shape on the hip joint contact stress. Combined with reverse engineering technique, surface-fitting algorithms and mathematical curve...
Bone is a strongly heterogeneous natural composite with microstructure. Although the classical theory of linear elasticity has been largely used in bone ultrasonic studies, it cannot sufficiently describe the mechanical behavior of materials with microstructure. Furthermore, this theory predicts non-dispersive behavior of Rayleigh waves, which is in conflict with experimental observations. By using...
The aim of this paper is to introduce effects well known to clinicians -but neglected to date- in the biomechanical modelling of breast malignant tumours. We develop a model of an isolated stellate breast tumour under mammographic compression forces. We study a range of reported mechanical properties, both linear elastic and hyperelastic. We also introduce different volumes of increased density/stiffness...
Manipulation of stem cells is one of the highest goals within biological sciences for the development of devices for the regeneration of injured tissues. In general, the mechanical properties of cells are nowadays recognized to play a role in many cellular phenotypes, including mobility though tissues, survival to mechanical loading and differentiation. Here we present a study where the mechanics...
Fluid structure interaction (FSI) simulations of patient-specific fusiform non-ruptured and contained ruptured Abdominal Aortic Aneurysm (AAA) geometries were conducted. The goals were: (1) to test the ability of our FSI methodology to predict the location of rupture, by correlating the high wall stress regions with the rupture location, (2) estimate the state of the pathological condition by calculating...
A custom, patient-specific unicompartmental knee replacement was developed using a unsupervised neural network trained on a database of healthy knee geometries. This custom implant was then compared to a conventional implant in terms of contact stress in a Finite Element Model. The custom implant experienced lower contact stresses at the tibiofemoral joint compared to the conventional implant. The...
The lack of reliable mechanical data on coronary arteries and, more specifically, on their wall strength hampers the application of numerical models and simulations to vascular problems, and precludes physicians from knowing in advance the response of coronary arteries to the different interventions. Studies of the mechanical properties of coronary arteries have been carried out almost exclusively...
Growth rate of abdominal aortic aneurysm (AAA) is thought to be an important indicator of the potential risk of rupture. Wall stress is also thought to be a trigger for its rupture. However, stress change during the expansion of an AAA is unclear. Forty-four patients with AAAs were included in this longitudinal follow-up study. They were assessed by serial abdominal ultrasonography and computerized...
Progress toward understanding the thermo-mechanical behavior of isolated cardiac muscle, excised from either healthy or diseased heart, is contingent on being able to measure simultaneously the stress (force per cross-sectional area) and heat production. Determination of dynamic modulus (dynamic stiffness times muscle length per cross-sectional area) sheds further light on the behavior of the force-and...
A system was built to test the efficacy of bacterial biofilm disruption using laser generated shockwaves. The system is based on a Q-switched, ND:YAG pulsed laser operating at a rep rate of 10 Hz with 1500 mJ pulses centered at 1064 nm. The laser pulses were used to create shockwave pulses in Al coated polycarbonate substrates and a resulting peak stress of greater than 50 MPa was measured. These...
The lack of reliable mechanical data on coronary arteries hampers the application of numerical models to vascular problems, and precludes physicians from knowing in advance the response of coronary arteries to the different interventions. In this work, the mechanical properties of human coronary arteries have been characterized. Whole samples from human right (RC) and left anterior descending (LAD)...
Efficient mechanical tools for the structural optimization of variable fixation apparatuses are presented in this study. The defect model prepared from 24 ulna-radius specimens are fixated respectively and randomly with new designed internal fixation panel, AO 4 holes panel, one-side external fixation bracket of Zimmer and negative comparison group, different experimental data are analyzed. Through...
In this paper, a three-dimensional (3D) FE model of the healthy human upper cervical vertebrae (C0–C3) was built having considered cortical and cancellous bone. The model was validated using numerical results obtained by other authors. The stress distribution and potential fracture patterns of the atlas were analyzed under different loads and force moments in 3 conditions. The results of FE analysis...
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