Finite element modeling and experimental verification of lower extremity shape change under load (original) (raw)
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Annals of Biomedical Engineering
Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-tibial amputation (TTA) patient, since a misfit may cause pressure ulcers or a deep tissue injury (DTI: necrosis of the muscle flap under intact skin) in the residual limb. To date, prosthetic fitting typically depends on the subjective skills of the prosthetist, and is not supported by biomedical instrumentation that allows evaluation of the quality of fitting. Specifically, no technology is presently available to provide real-time continuous information on the internal distribution of mechanical stresses in the residual limb during fitting of the prosthesis, or while using it and this severely limits patient evaluations. In this study, a simplified yet clinically oriented patient-specific finite element (FE) model of the residual limb was developed for real-time stress analysis. For this purpose we employed a custom-made FE code that continuously calculates internal stresses in the resid...
Finite element analysis of the amputated lower limb: A systematic review and recommendations
Medical Engineering & Physics, 2017
The care and rehabilitation of individuals after lower limb amputation presents a substantial and growing socioeconomic challenge. Clinical outcome is closely linked to successful functional rehabilitation with a prosthetic limb, which depends upon comfortable prosthetic limb-residual limb load transfer. Despite early interest in the 1980s, the amputated limb has received considerably less attention in computational biomechanical analysis than other subjects, such as arthroplasty. This systematic literature review investigates the state of the art in residual limb finite element analysis published since 20 0 0. The identified studies were grouped into the following categories: (1) residuum-prosthesis interface mechanics; (2) residuum soft tissue internal mechanics; (3) identification of residuum tissue characteristics; (4) proposals for incorporating FEA into the prosthesis fitting process; (5) analysis of the influence of prosthetic componentry concepts to improve load transfer to the residuum, such as the monolimb and structural socket compliance; and (6) analysis of osseointegrated (OI) prostheses. The state of the art is critically appraised in order to form recommendations for future modeling studies in terms of geometry, material properties, boundary conditions, interface models, and relevant but un-investigated issues. Finally, the practical implementation of these approaches is discussed.
The Iowa orthopaedic journal, 2003
Joint implant design clearly affects long-term outcome. While many implant designs have been empirically-based, finite element analysis has the potential to identify beneficial and deleterious features prior to clinical trials. Finite element analysis is a powerful analytic tool allowing computation of the stress and strain distribution throughout an implant construct. Whether it is useful depends upon many assumptions and details of the model. Since ultimate failure is related to biological factors in addition to mechanical, and since the mechanical causes of failure are related to load history, rather than a few loading conditions, chief among them is whether the stresses or strains under limited loading conditions relate to outcome. Newer approaches can minimize this and the many other model limitations. If the surgeon is to critically and properly interpret the results in scientific articles and sales literature, he or she must have a fundamental understanding of finite element ...
Wseas Transactions on Computers, 2009
The inclusion of analytical and experimental models in biomechanical studies leads to the obtainment of important data for the research concerning the human skeleton, its traumas and diseases. The paper showcases a number of results regarding the static and dynamic analysis of some biomechanical components by using the finite element method (FEM). Models, representing parts of the human upper limb, have been studied using static trials. Considering the fact that we wish to emphasize the way in which such analyses can be done with a finite element method, we shall present only a few relevant examples for which we have experimental data, namely: analysis of the compression, bending and stretching of the humerus and bending of the radius and the ulna.
ArXiv, 2019
Lower limb amputees often suffer skin and tissue problems from using their prosthesis which is a challenging biomechanical problem. The finite element method (FEM) has previously been applied to analyse internal mechanical conditions of the leg at prosthesis use. However, the representation of soft tissue was simplified to few layers and tissue types. The effects of such a simplification of human tissue is still unclear and the results from simplified models may be misleading. Thus, comparisons of the effects of using five versus six tissue types were performed on a transtibial cross section model exposed to three different socket designs. Skin, fat, vessels and bones were defined separately while muscle and fascia tissues were separate or merged. Nonlinear behaviour and friction between socket and skin were considered in the simulations. Contact forces as well as internal stresses and strains of each tissue type differed in both magnitude and maxima site for each material set withi...
Finite element model of a below-knee amputation: a feasibility study
Computer Methods in Biomechanics and Biomedical Engineering, 2017
a a laboratoire de Biomécanique appliquée; b College of Vehicle and mechanical engineering, hunan university, China; c hôpital d'instruction des armées de laveran KEYWORDS trans-tibial amputation; lower limb prosthesis; optimization; socket pressures; finite element model
Modeling and Finite Element Analysis of Knee Prosthesis with and without Implant
Biomechanics is the study of the structure and function of biological systems by means of the methods of “mechanics” which is the branch of physics involving analysis of the actions of forces. Knee joint is the complex structure of the human body acquires the critical loads in various moving conditions. This paper discusses the loads acting on the joint during different motions such as steady, walking and lifting. A 3d modeling software PRO/E is used to prepare a CAD model of knee prosthesis and evaluate the results in the form of stresses by applying the calculated loads in the finite element analysis software ANSYS. The stresses are evaluated by considering several cases of loading. The aim is to study and evaluate the loads and stresses acting on knee joint and compared with the implant results.
2009
The work presents a few results regarding the static and dynamic analysis of some biomechanical components through the finite element method. Models, representing parts of the human upper limb, have been studied using static trials. Another study was carried out in order to determine the dynamic behavior of the model for total arm prosthesis. The models have been created with the aid of the SolidWorks program and the trials with the HyperMesh program. Considering the fact that we wish to emphasize the way in which such analyses can be done with a finite element method, from meshing to the obtaining of results, as well as their comparison to the results obtained experimentally, we shall present only a few relevant examples for such studies.
Finite element analysis of two total knee joint prostheses
International Journal on Interactive Design and Manufacturing (IJIDeM), 2012
Aim of this work is to compare two different total knee prostheses that differ mainly in the shape of the polyethylene (PE) component inserted between the femoral and tibial plates. The best solution between them has been originally reshaped in order to reduce stress peaks. The study procedure has been divided into the following steps. First step is the digitalisation of the shape of the prostheses by means of a 3D laser scanner. The morphology of two prototypes of the prostheses has been acquired by elaborating multiple Moirè fringe patterns projected on their surfaces. Second step consisted on the manipulation of these data in a CAD module, that is the interpolation of raw data into NURBS surfaces, reducing singularities due to the typical scattering of the acquiring system. Third step has been the setting up of FEM simulations to evaluate the prostheses behaviour under benchmark loading conditions given in literature. The CAD model of the prostheses has been meshed into solid finite elements. Different flexion angles configurations have been analysed, the load being applied along the femoral axis. FEM analyses have returned stress fields in the PE insert and, in particular, in the stabilizing cam which function is to avoid dislocation. Last step has been the integrated use of CAD T. Ingrassia · V. Nigrelli · V. Ricotta
Experimental validation of a finite element model of a human cadaveric tibia
Journal of biomechanical engineering, 2008
Finite element (FE) models of long bones are widely used to analyze implant designs. Experimental validation has been used to examine the accuracy of FE models of cadaveric femurs; however, although convergence tests have been carried out, no FE models of an intact and implanted human cadaveric tibia have been validated using a range of experimental loading conditions. The aim of the current study was to create FE models of a human cadaveric tibia, both intact and implanted with a unicompartmental knee replacement, and to validate the models against results obtained from a comprehensive set of experiments. Seventeen strain rosettes were attached to a human cadaveric tibia. Surface strains and displacements were measured under 17 loading conditions, which consisted of axial, torsional, and bending loads. The tibia was tested both before and after implantation of the knee replacement. FE models were created based on computed tomography (CT) scans of the cadaveric tibia. The models consisted of ten-node tetrahedral elements and used 600 material properties derived from the CT scans. The experiments were simulated on the models and the results compared to experimental results. Experimental strain measurements were highly repeatable and the measured stiffnesses compared well to published results. For the intact tibia under axial loading, the regression line through a plot of strains predicted by the FE model versus experimentally measured strains had a slope of 1.15, an intercept of 5.5 microstrain, and an R 2 value of 0.98. For the implanted tibia, the comparable regression line had a slope of 1.25, an intercept of 12.3 microstrain, and an R 2 value of 0.97. The root mean square errors were 6.0% and 8.8% for the intact and implanted models under axial loads, respectively. The model produced by the current study provides a tool for simulating mechanical test conditions on a human tibia. This has considerable value in reducing the costs of physical testing by pre-selecting the most appropriate test conditions or most favorable prosthetic designs for final mechanical testing. It can also be used to gain insight into the results of physical testing, by allowing the prediction of those variables difficult or impossible to measure directly.