The computer simulation of wear behavior appearing in total hip prosthesis (original) (raw)
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The computer simulation of wear behavior appearing in total hip prosthesis* 1
Computer methods and programs …, 2003
Computer algorithms are proposed for the estimation of wear appearing in artificial hip joints using finite element analysis based on the modified Archard's wear law, contact features and an analogue wear process. A pin-on-disk plate experiment is reconstructed to assess the efficiency and validity of the algorithms proposed here. Through the successful verification of wear depth and volume loss of the pin-on-disk plate as well as the artificial hip joint, the current algorithms provide significant agreement with experiments, clinical measurements and numerical calculations and are shown to be both valid and feasible. Further investigation into the effect of femoral heads with various sizes suggests that the larger femoral head may induce larger wear volume but gives a smaller wear depth and that wear depth and volume loss are apparently nonlinearly related to the femoral head diameter. It is shown that the current algorithms are useful and helpful in understanding wear behavior for alternative or new designs of artificial hip joints and even for other analogous structures.
A Comparative Study on Wear Behavior of Hip Prosthesis by Finite Element Simulation
Biomedical Engineering: Applications, Basis and Communications, 2002
A numerical approach was proposed to investigate the wear behavior occurred in the artificial hip joints in this paper. In the numerical simulations, the wear coefficients taken from pin-on-disk tests were introduced into the wear analysis model to assess the wear rates of polyethylene acetabular cups against metallic or ceramic femoral heads. For the established material combinations, different values of polyethylene wear rates were obtained respectively, which were not necessarily the realistic one as expected in vivo but could be confirmed after further discussion on the wear mechanism involved in wear tests. Current results indicated that the polyethylene/ceramic couples represented better wear performances than the polyethylene/metal couples. Furthermore, the ratio of wear rates for polyethylene cups against alumina and the metallic femoral heads was 0.5, which agreed well with that deduced from clinical studies or laboratory hip simulators. It is obvious that these comparable ...
Facta Universitatis, 2016
The existing model of wear, based on the classical Archard equation, in the spherical joint of a total hip prosthesis comprising an acetabular cup of ultra-high molecular weight polyethylene (UHMWPE) in combination with a metal or ceramic femoral head is modified and expanded. With this model, studies are conducted using the finite element analysis in terms of cumulative linear and volumetric wear for the ISO 14242-1 demands and additionally for the conditions during walking gait. Also they are carried out for the head diameter of 28 mm at the constant and the variable wear factor, where the variable wear factor is adopted from the modified formula for the dependence on the contact pressure.
Predicting the wear of hard-on-hard hip joint prostheses
Wear, 2013
The wear of the bearing surfaces of hip joint prostheses is a key problem causing their primary failure. This paper introduces a wear prediction model with the aid of the finite element analysis. To mimic walking, the most common activity of a human body, a three-dimensional physiological loading gait cycle was considered. The wear at the bearing surface in gait cycles was calculated based on the contact stress variation from the finite element analysis and the sliding distance obtained from threedimensional hip gait motions. The geometry of the worn surface was updated considering the average routine activities of a patient. The model was applied to three hard-on-hard prostheses, i.e., PCD (polycrystalline diamond)-on-PCD, ceramic-on-ceramic and metal-on-metal couples. It was found that due to the gait motion, the intensity and location of the maximum contact stress in the bearing components change with the gait instances. With a given geometry and gait loading, the linear and volumetric wear on the cup surface increases with the number of gait cycles. With increasing the gait cycles, the surface wear can bring about scattered contact pressure distribution. Compared to the ceramic-on-ceramic and metal-on-metal couples, the PCD-on-PCD bearing has the lowest wear progression. It was also concluded that the computational wear model presented in this paper can reasonably predict the wear evolution in hard-on-hard hip implants.
The advanced model of wear in the spherical joint of total hip prosthesis comprising an acetabular cup of ultra-high molecular weight polyethylene (UHMWPE) in combination with a metal or ceramic femoral head is developed. The wear model is based on the classical Archard-Lancaster equation in common with all other studies reported in literature. The finite element solution of the contact problem between the cup and the head was employed under the loading and angular motions conditions according to the ISO 14242-1 demands. The polymer wear in terms of cumulative linear and volume wear when the wear factor is chosen to be a function of contact pressure is first evaluated.
Computational model of wear mechanisms for total hip joint replacement
2005
This thesis presents a study of wear mechanisms for total hip replacements (THRs) utilizing both the finite element method (FEM) and laboratory experiment. The hip prosthesis studied consists of an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup articulating against a cobalt-chromium (CoCr) alloy femoral head. According to the geometrical scale, the FEM models developed can be divided into two categories, the first deals with a macro-scale whilst the second treats a micro-scale (asperity) geometry model. The macro-scale FEM model aims to analyse various aspects of the prosthesis, for instance, bulk material, surface stress and temperature rise under variable conditions of elastic modulus, friction coefficient, sliding speed and radial clearance. In this analysi apart from the CoCr alloy head, an alumina femoral head model is also included in the angle between the direction of wear and a plane parallel to the flat face ofthe cup von Mises stress (MPa)
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2001
This paper presents an analytical model of the cobalt-based alloy-ultra-high molecular weight polyethylene ( UHMWPE ) wear coupling. Based on a previous model in which the cup wear volume over a gait cycle ( WG ) was calculated under the simplifying assumption of an ideal rigid coupling, the current version proposes a more realistic wear simulation. All three components of the hip loading force were considered for the contact pressure calculation and all three components of the hip motion were taken into account for the sliding distance calculation. The contact pressure distribution was calculated on the basis of the Hertzian theory for the elastic contact of two bodies with non-conforming geometrical shapes. The wear factor was taken from hip simulator wear tests. The calculated WG is 67610Õ6 mm3 for a standard reference patient. The parametric model simulations show that WG increases linearly with the patient weight, femoral head diameter and surface roughness. It increases non-linearly to a maximum and decreases to an asymptotic value with increasing cup/head clearance and with cup isotropic elastic modulus. The cup orientation in the pelvis aVects only slightly the total amount of WG whereas it is the dominant factor aVecting the shape of the wear distribution. The iso-wear maps show paracentral patterns at low cup inclination angles and marginal patterns at higher inclination angles. The maximum wear depth is supero-posterior when the cup is in neutral alignment and supero-anterior at increasing anteversion angles. Complex patterns with a combination of paracentral and marginal wear were obtained at speci c clearance values and cup orientations. The results of the simulations are discussed in relation to the wear distribution measured on the articular surface of 12 UHMWPE components retrieved from failed hip joint prostheses, after a period of in situ functioning.
Facta Universitatis, 2018
The present study assesses the impact of the main typical activities of patients' daily living (ADL) after total hip arthroplasty (THA) on the wear parameters of sliding couple's materials by simulating linear and volumetric wear according to the Archard's law in a spherical joint with a polymeric element of the total hip replacement (THR). The mathematical wear model, built on the basis of algorithms and custom codes of the finite element analysis in ANSYS and MATLAB software systems, has been studied numerically. The activities used in the model are: level walking, stair ascending-stair descending, chair sitting-chair rising, and deep squatting. They were described by typical waveforms of the angular displacements of the THR's femoral component and the waveforms of the applied force. The results of the simulation show that for the same duration the overall wear value with ADL is significantly higher than in the case of level walking according to the requirements of ISO 14242-1. Therefore, the evaluation of the wear value for ADL is more informative for predicting the functional life time of the THR. Analysis of the simulation results shows that the amount of wear calculated for all activities separately is practically the same as the overall wear value obtained at summary action of ADL. This effect of the independence of contributions to the total amount of wear of each activity makes it possible to significantly simplify the solution of the problem of wear estimation for typical activities, including stochastic ones.
Effect of motion inputs on the wear prediction of artificial hip joints
Tribology international, 2013
Hip joint simulators have been largely used to assess the wear performance of joint implants. Due to the complexity of joint movement, the motion mechanism adopted in simulators varies. The motion condition is particularly important for ultra-high molecular weight polyethylene (UHMWPE) since polyethylene wear can be substantially increased by the bearing cross-shear motion. Computational wear modelling has been improved recently for the conventional UHMWPE used in total hip joint replacements. A new polyethylene wear law is an explicit function of the contact area of the bearing and the sliding distance, and the effect of multidirectional motion on wear has been quantified by a factor, cross-shear ratio. In this study, the full simulated walking cycle condition based on a walking measurement and two simplified motions, including the ISO standard motion and a simplified ProSim hip simulator motion, were considered as the inputs for wear modelling based on the improved wear model. Bot...