1,721,087 research outputs found
Cell population dynamics and oxygen transport in engineered tissue: a coupled Lattice-Boltzmann cellular automata model
No full textFinite element comparison between the human and the ovine lumbar intervertebral disc
No full textIntroduction: Nowadays it is still not clear which loading conditions are responsible for lumbar intervertebral disc failure. Many studies have been conducted to investigate the effect of different loading conditions on the herniation processes, and many of them were based on the ovine model. However, the biomechanical similarities between the human and the ovine lumbar disc have been demonstrated in the main planes only, whereas it is not known if they are comparable under complex loading conditions too. The aim of this study was to compare the mechanical response of the ovine and the human lumbar intervetebral disc under complex loading conditions, in order to investigate differences and similarities between the species.The loading scenarios described in a finite element study on a human lumbar segment were applied to a model of the ovine disc, and the results were then compared.It has been shown that combined loads generated highest strains in both the models, and the maximum strains had the same location in the posterior or in the postero-lateral region of the annulus, according to the loading scenario.Conclusion: The ovine disc can be used in spinal research to investigate herniation process under any loading conditions
Computational modeling of combined cell population dynamics and oxygen transport in engineered tissue subject to interstitial perfusion
No full textImage-based biomechanical models of the musculoskeletal system
Full text linkFinite element modeling is a precious tool for the investigation of the biomechanics of the musculoskeletal system. A key element for the development of anatomically accurate, state-of-the art finite element models is medical imaging. Indeed, the workflow for the generation of a finite element model includes steps which require the availability of medical images of the subject of interest: segmentation, which is the assignment of each voxel of the images to a specific material such as bone and cartilage, allowing for a three-dimensional reconstruction of the anatomy; meshing, which is the creation of the computational mesh necessary for the approximation of the equations describing the physics of the problem; assignment of the material properties to the various parts of the model, which can be estimated for example from quantitative computed tomography for the bone tissue and with other techniques (elastography, T1rho, and T2 mapping from magnetic resonance imaging) for soft tissues. This paper presents a brief overview of the techniques used for image segmentation, meshing, and assessing the mechanical properties of biological tissues, with focus on finite element models of the musculoskeletal system. Both consolidated methods and recent advances such as those based on artificial intelligence are described
The Simulation of Muscles Forces Increases the Stresses in Lumbar Fixation Implants with Respect to Pure Moment Loading
Full text linkSimplified loading conditions such as pure moments are frequently used to compare different instrumentation techniques to treat spine disorders. The purpose of this study was to determine if the use of realistic loading conditions such as muscle forces can alter the stresses in the implants with respect to pure moment loading. A musculoskeletal model and a finite element model sharing the same anatomy were built and validated against in vitro data, and coupled in order to drive the finite element model with muscle forces calculated by the musculoskeletal one for a prescribed motion. Intact conditions as well as a L1-L5 posterior fixation with pedicle screws and rods were simulated in flexion-extension and lateral bending. The hardware stresses calculated with the finite element model with instrumentation under simplified and realistic loading conditions were compared. The ROM under simplified loading conditions showed good agreement with in vitro data. As expected, the ROMs between the two types of loading conditions showed relatively small differences. Realistic loading conditions increased the stresses in the pedicle screws and in the posterior rods with respect to simplified loading conditions; an increase of hardware stresses up to 40 MPa in extension for the posterior rods and 57 MPa in flexion for the pedicle screws were observed with respect to simplified loading conditions. This conclusion can be critical for the literature since it means that previous models which used pure moments may have underestimated the stresses in the implants in flexion-extension and in lateral bending
Investigation of the state of stress generated by high loads in the ovine lumbar intervertebral disc using a new anisotropic hyperelastic model
No full textDisc herniation is one of the main causes of low back pain, and it is the pathologic condition for which spinal surgery is most often required. Many experimental and numerical studies have been conducted to investigate the mechanical failure of the intervertebral disc (IVD); however, there is not in the literature a study that defines a mechanical criterion for the disc failure. The aim of this study was to investigate the state of stress generated by the application of high loads and to define which state of stress was the most responsible for herniation. A finite element model of the ovine lumbar IVD was developed. The loading scenarios applied in an experimental study taken from the literature were applied, and the results compared to define the failure conditions. Then the effect of combined and simple rotations was investigated as well. It was found that an axial stress higher than 10 MPa in the posterior region of the annulus has a high probability of damaging the disc, and that flexion had a main role in damaging annulus tissue
Loss of mechanical contact of cementless acetabular prostheses due to post-operative weight bearing: a biomechanical model
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Multibody modelling of the cervical spine in the simulation of flexion-extension after disc arthroplasty
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