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Computer Methods in Biomechanics and Biomedical Engineering

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November 29, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Ralf Gutwald, Raimund Jaeger, Floor M Lambers
The purpose of this paper was to analyze the biomechanical performance of customized mandibular reconstruction plates with optimized strength. The best locations for increasing bar widths were determined with a sensitivity analysis. Standard and customized plates were mounted on mandible models and mechanically tested. Maximum stress in the plate could be reduced from 573 to 393 MPa (-31%) by increasing bar widths. The median fatigue limit was significantly greater (p < 0.001) for customized plates (650 ± 27 N) than for standard plates (475 ± 27 N)...
November 25, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Patrick D Wettenschwiler, Silvio Lorenzetti, Stephen J Ferguson, Rolf Stämpfli, Ameet K Aiyangar, René M Rossi, Simon Annaheim
Backpack carriage is significantly associated with a higher prevalence of low back pain. Elevated compression and shear forces in the lumbar intervertebral discs are known risk factors. A novel method of calculating the loads in the lumbar spine during backpack carriage is presented by combining physical and numerical modelling. The results revealed that to predict realistic lumbar compression forces, subject-specific lumbar curvature data were not necessary for loads up to 40 kg. In contrast, regarding shear forces, using subject-specific lumbar curvature data from upright MRI measurements as input for the rigid body model significantly altered lumbar joint force estimates...
November 22, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Dimitra Blana, Edward K Chadwick, Antonie J van den Bogert, Wendy M Murray
Individuals with hand amputation suffer substantial loss of independence. Performance of sophisticated prostheses is limited by the ability to control them. To achieve natural and simultaneous control of all wrist and hand motions, we propose to use real-time biomechanical simulation to map between residual EMG and motions of the intact hand. Here we describe a musculoskeletal model of the hand using only extrinsic muscles to determine whether real-time performance is possible. Simulation is 1.3 times faster than real time, but the model is locally unstable...
November 20, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Sadegh Naserkhaki, Marwan El-Rich
The follower load (FL) combined with moments is commonly used to approximate flexed/extended posture of the lumbar spine in absence of muscles in biomechanical studies. There is a lack of consensus as to what magnitudes simulate better the physiological conditions. Considering the in-vivo measured values of the intradiscal pressure (IDP), intervertebral rotations (IVRs) and the disc loads, sensitivity of these spinal responses to different FL and flexion moment magnitudes was investigated using a 3D nonlinear finite element (FE) model of ligamentous lumbosacral spine...
November 16, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Zhao Ying Cui, Nele Famaey, Bart Depreitere, Jan Ivens, Svein Kleiven, Jos Vander Sloten
Acute subdural hematoma (ASDH) is a type of intracranial haemorrhage following head impact, with high mortality rates. Bridging vein (BV) rupture is a major cause of ASDH, which is why a biofidelic representation of BVs in finite element (FE) head models is essential for the successful prediction of ASDH. We investigated the mechanical behavior of BVs in the KTH FE head model. First, a sensitivity study quantified the effect of loading conditions and mechanical properties on BV strain. It was found that the peak rotational velocity and acceleration and pulse duration have a pronounced effect on the BV strains...
November 14, 2016: Computer Methods in Biomechanics and Biomedical Engineering
E J Mathias, M J Plank, T David
The mechanisms with which neurons communicate with the vasculature to increase blood flow, termed neurovascular coupling is still unclear primarily due to the complex interactions between many parameters and the difficulty in accessing, monitoring and measuring them in the highly heterogeneous brain. Hence a solid theoretical framework based on existing experimental knowledge is necessary to study the relation between neural activity, the associated vasoactive factors released and their effects on the vasculature...
November 11, 2016: Computer Methods in Biomechanics and Biomedical Engineering
E J Mathias, M J Plank, T David
A mathematical model is developed which describes a signalling mechanism of neurovascular coupling with a model of a pyramidal neuron and its corresponding fMRI BOLD response. In the first part of two papers (Part I) we described the integration of the neurovascular coupling unit extended to include a complex neuron model, which includes the important Na/K ATPase pump, with a model that provides a BOLD signal taking its input from the cerebral blood flow and the metabolic rate of oxygen consumption. We showed that this produced a viable signal in terms of initial dip, positive and negative BOLD signals...
November 11, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Olivia Miraucourt, Stéphanie Salmon, Marcela Szopos, Marc Thiriet
The development of a software platform incorporating all aspects, from medical imaging data, through three-dimensional reconstruction and suitable meshing, up to simulation of blood flow in patient-specific geometries, is a crucial challenge in biomedical engineering. In the present study, a fully three-dimensional blood flow simulation is carried out through a complete rigid macrovascular circuit, namely the intracranial venous network, instead of a reduced order simulation and partial vascular network. The biomechanical modeling step is carefully analyzed and leads to the description of the flow governed by the dimensionless Navier-Stokes equations for an incompressible viscous fluid...
November 1, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Kevin M Moerman, Marc van Vijven, Leandro R Solis, Eline E van Haaften, Arjan C Y Loenen, Vivian K Mushahwar, Cees W J Oomens
Pressure ulcers are a type of local soft tissue injury due to sustained mechanical loading and remain a common issue in patient care. People with spinal cord injury (SCI) are especially at risk of pressure ulcers due to impaired mobility and sensory perception. The development of load improving support structures relies on realistic tissue load evaluation e.g. using finite element analysis (FEA). FEA requires realistic subject-specific mechanical properties and geometries. This study focuses on the effect of geometry...
November 1, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Siamak N Doost, Liang Zhong, Boyang Su, Yosry S Morsi
The image-based computational fluid dynamics (IB-CFD) technique, as the combination of medical images and the CFD method, is utilized in this research to analyze the left ventricle (LV) hemodynamics. The research primarily aims to propose a semi-automated technique utilizing some freely available and commercial software packages in order to simulate the LV hemodynamics using the IB-CFD technique. In this research, moreover, two different physiological time-resolved 2D models of a patient-specific LV with two different types of aortic and mitral valves, including the orifice-type valves and integrated with rigid leaflets, are adopted to visualize the process of developing intraventricular vortex formation and propagation...
October 31, 2016: Computer Methods in Biomechanics and Biomedical Engineering
C Pizzolato, M Reggiani, L Modenese, D G Lloyd
Real-time estimation of joint angles and moments can be used for rapid evaluation in clinical, sport, and rehabilitation contexts. However, real-time calculation of kinematics and kinetics is currently based on approximate solutions or generic anatomical models. We present a real-time system based on OpenSim solving inverse kinematics and dynamics without simplifications at 2000 frame per seconds with less than 31.5 ms of delay. We describe the software architecture, sensitivity analyses to minimise delays and errors, and compare offline and real-time results...
October 10, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Elizabeth C Clarke, David F Fletcher, Lynne E Bilston
Syringomyelia (a spinal cord cyst) usually develops as a result of conditions that cause cerebrospinal fluid (CSF) obstruction. The mechanism of syrinx formation and enlargement remains unclear, though previous studies suggest that the fluid enters via the perivascular spaces (PVS) of the penetrating arteries of the spinal cord, and that alterations in the CSF pulse timing and pressure could contribute to enhanced PVS inflow. This study uses an idealised computational model of the PVS to investigate the factors that influence peri-arterial fluid flow...
October 7, 2016: Computer Methods in Biomechanics and Biomedical Engineering
K Cao, P Sucosky
Computational characterizations of aortic valve hemodynamics have typically discarded the effects of coronary flow. The objective of this study was to complement our previous fluid-structure interaction aortic valve model with a physiologic coronary circulation model to quantify the impact of coronary flow on aortic sinus hemodynamics and leaflet wall shear stress (WSS). Coronary flow suppressed vortex development in the two coronary sinuses and altered WSS magnitude and directionality on the three leaflets, with the most substantial differences occurring in the belly and tip regions...
October 7, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Yu-Ching Yang, Haw-Long Lee, Win-Jin Chang, Wen-Lih Chen
The aim of this study is to solve an inverse heat conduction problem to estimate the unknown time-dependent laser irradiance and thermal damage in laser-irradiated biological tissue from the temperature measurements taken within the tissue. The dual-phase-lag model is considered in the formulation of heat conduction equation. The inverse algorithm used in the study is based on the conjugate gradient method and the discrepancy principle. The effect of measurement errors and measurement locations on the estimation accuracy is also investigated...
October 6, 2016: Computer Methods in Biomechanics and Biomedical Engineering
M D Gilchrist, D MacManus, J G Murphy, B Pierrat
In order to avoid the numerical difficulties in locally enforcing the incompressibility constraint using the displacement formulation of the Finite Element Method, slight compressibility is typically assumed when simulating the mechanical response of arterial tissue. The current standard method of accounting for slight compressibility of hyperelastic soft tissue assumes an additive decomposition of the strain-energy function into a volumetric and a deviatoric part. This has been shown, however, to be inconsistent with the linear theory and results in cubes retaining their cuboid shape under hydrostatic tension and compression, which seems at variance with the reinforcement of arterial tissue with two families of collagen fibres...
October 6, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Maki Matsuzaki, Yasunori Ayukawa, Nobuo Sakai, Tatsuya Matsuzaki, Yasuyuki Matsushita, Kiyoshi Koyano
A number of finite element analyses (FEAs) for the dental implant were performed without regard for preload and with all interfaces 'fixed-bonded'. The purpose of this study was comparing the stress distributions between the conventional FEA model with all contacting interfaces 'fixed-bonded' (bonded model) and the model with the interfaces of the components in 'contact' with friction simulated as a preloaded implant (contact model). We further verified the accuracy of the result of the FEA using model experiment...
September 28, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Daisuke Tawara, Ken Nagura
Because changes in the mechanical properties of bone are closely related to trabecular bone remodeling, methods that consider the temporal morphological changes induced by adaptive remodeling of trabecular bone are needed to estimate long-term fracture risk and bone quality in osteoporosis. We simulated bone remodeling using simplified and pig trabecular bone models and estimated the morphology of healthy and osteoporotic cases. We then displayed the fracture risk of the remodeled models based on a cumulative histogram from high stress...
September 27, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Naiara Rodriguez-Florez, Alessandra Carriero, Sandra J Shefelbine
This study aimed at using eXtended finite element method (XFEM) to characterize crack growth through bone's intra-cortical pores. Two techniques were compared using Abaqus: (1) void material properties were assigned to pores; (2) multiple enrichment regions with independent crack-growth possibilities were employed. Both were applied to 2D models of transverse images of mouse bone with differing porous structures. Results revealed that assigning multiple enrichment regions allows for multiple cracks to be initiated progressively, which cannot be captured when the voids are filled...
September 22, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Michael E Stender, Richard A Regueiro, Virginia L Ferguson
The changes experienced in synovial joints with osteoarthritis involve coupled chemical, biological, and mechanical processes. The aim of this study was to investigate the consequences of increasing permeability in articular cartilage (AC), calcified cartilage (CC), subchondral cortical bone (SCB), and subchondral trabecular bone (STB) as observed with osteoarthritis. Two poroelastic finite element models were developed using a depth-dependent anisotropic model of AC with strain-dependent permeability and poroelastic models of calcified tissues (CC, SCB, and STB)...
September 16, 2016: Computer Methods in Biomechanics and Biomedical Engineering
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