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Ball-in-socket configurations for artificial hip replacements, (a) anatomical model with the three-dimensional loads and motions, (b) horizontal model with the vertical load and flexionextension motion.
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This paper reviews the recent advancements in computational modelling of the lubrication of hip and knee joint replacements, especially those concerning Professor Duncan Dowson’s contribution. The review starts with the development of modelling the five key parameters that appeared in the pioneered Hamrock–Dowson formula. Then, the theory and appro...
Contexts in source publication
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... typical artificial hip joint, consisting of a femoral head and an acetabular cup, is often simplified as a ball-in-socket model. Anatomically, the acetabular cup is positioned in the human pelvis or cup holder of a joint simulator with an inclined angle between 30 • to 45 • , illustrated as the angle α between the blue and red coordinate system in Figure 1a. The red coordinate system, having the y-axis pointing in the superior direction, rotates by an angle α along its z-axis to form the blue coordinate system. ...
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... red coordinate system, having the y-axis pointing in the superior direction, rotates by an angle α along its z-axis to form the blue coordinate system. In Figure 1, angles θ and ϕ are spherical coordinates, which are often used to describe the lubrication governing equations for the hip joint model; w indicates loading and ω indicates the rotations. It is reasonable to rotate the cup into a horizontal position when the contact area is within the cup and away from the contact edge, as shown in Figure 1b, without affecting the lubrication results [21,22]. ...
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... Figure 1, angles θ and ϕ are spherical coordinates, which are often used to describe the lubrication governing equations for the hip joint model; w indicates loading and ω indicates the rotations. It is reasonable to rotate the cup into a horizontal position when the contact area is within the cup and away from the contact edge, as shown in Figure 1b, without affecting the lubrication results [21,22]. However, such a simplified rotation would not apply when there is an edge-loading contact. ...
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... red coordinate system, having the y-axis pointing in the superior direction, rota by an angle along its z-axis to form the blue coordinate system. In Figure 1, ang and are spherical coordinates, which are often used to describe the lubrication go erning equations for the hip joint model; w indicates loading and indicates the ro tions. It is reasonable to rotate the cup into a horizontal position when the contact area within the cup and away from the contact edge, as shown in Figure 1b, without affecti the lubrication results [21,22]. ...
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... Figure 1, ang and are spherical coordinates, which are often used to describe the lubrication go erning equations for the hip joint model; w indicates loading and indicates the ro tions. It is reasonable to rotate the cup into a horizontal position when the contact area within the cup and away from the contact edge, as shown in Figure 1b, without affecti the lubrication results [21,22]. However, such a simplified rotation would not apply wh there is an edge-loading contact (a) (b) Figure 1. ...
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... is reasonable to rotate the cup into a horizontal position when the contact area within the cup and away from the contact edge, as shown in Figure 1b, without affecti the lubrication results [21,22]. However, such a simplified rotation would not apply wh there is an edge-loading contact (a) (b) Figure 1. Ball-in-socket configurations for artificial hip replacements, (a) anatomical model with three-dimensional loads and motions, (b) horizontal model with the vertical load and flexiontension motion. ...
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... details on the main characteristics of the mixed lubrication models of hip and knee implants are summarised in Table 6. Some results of the film thickness and pressure from previous studies are compared in Figures 10 and 11 for hip and knee implants, respectively. It needs to be noted that the materials, geometry, loading, and motion conditions were not all the same among these studies, so the aim of presenting the results in one figure is to give readers a clue of the trend and range of the results, not to compare the results quantitively. ...
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... details on the main characteristics of the mixed lubrication models of hip and knee implants are summarised in Table 6. Some results of the film thickness and pressure from previous studies are compared in Figures 10 and 11 for hip and knee implants, respectively. It needs to be noted that the materials, geometry, loading, and motion conditions were not all the same among these studies, so the aim of presenting the results in one figure is to give readers a clue of the trend and range of the results, not to compare the results quantitively. ...
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... (b) Figure 10. Predicted film thickness in the mixed lubrication models of hip replacements [10,49]: (a) the minimum film thickness; (b) the maximum pressure (more details on materials and geometry are listed in Table 5). ...
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... film thickness in the mixed lubrication models of hip replacements [10,49]: (a) the minimum film thickness; (b) the maximum pressure (more details on materials and geometry are listed in Table 5). Figure 10. Predicted film thickness in the mixed lubrication models of hip replacements [10,49]: (a) the minimum film thickness; (b) the maximum pressure (more details on materials and geometry are listed in Table 5). ...
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... (b) Figure 11. Predicted film thickness in the mixed lubrication models of knee replacements: (a) lateral and (b) medial condyle (more details on the materials and geometry are listed in Table 6). ...
Citations
... However, the demands for arthroplasty have substantially increased over the past few years with a more active elderly population, while the average 15-20 year lifespan of these implants may not address the needs of younger patients [1,2]. Studies indicated that wear and debris are the main problems leading to the failure of joint implants, however, lubrication can considerably reduce these acute complications, increase the implant lifetime, and prevent revision surgery [1,3,4]. Notably, natural articulating joints are self-lubricating under load due to the intrinsic poro-elasticity of cartilage tissue and the self-pressurization of interstitial fluid [5,6]. ...
... Numerous lubricant simulation models [14][15][16] have been found to study the lubricant performance of the hip implant by measuring the lubricant film thickness. Hamrock and Dowson developed an analytical model to study the lubrication regime with respect to point contacts based on the system parameters. ...
The lubrication regime of a hip implant is influenced by various parameters, including material, geometry, roughness, relative angular movement, and loading circumstances. These factors impact friction and wear performance, ultimately limiting the implant’s longevity. In this study, a ball-on-plane model is considered to predict the lubrication regime across the entire gait cycle for the metal-on-metal and ceramic-on-ceramic hip implants. According to ISO 14242-1, a normal walking gait cycle is considered for the loads and rotations in the hip implant for this study. A comprehensive analysis is done to estimate the lubrication regime by considering different material combinations, body weights, femoral head sizes, clearances, and roughness across the entire gait cycle. The correlation coefficients show that the geometrical parameters are dominant in affecting the lubrication film thickness compared to the operational and material parameters. The femoral head size and body weight are found to be the most dominant and least dominant parameter respectively. Among the hard-on-hard tribo-pairs, ceramics operate predominantly in the full-film lubrication regime compared to metals due to its fine surface finish. The present research suggests that in order to maximise the longevity of a hip implant, an orthopaedic surgeon should choose one with a larger femoral head diameter, less clearance, and an ultra-fine surface finish, regardless of any material tribo-pair.
... Regarding numerical approaches to study the tribo-contacts in synovial joints, models based on the finite element method (FEM) assuming dry conditions have been widely developed (Donahue et al. 2002;O'Brien et al. 2015;Penrose et al. 2002) and even partly coupled to musculoskeletal multibodydynamics (Shu et al. 2018;Hua et al. 2022) as well as wear predictive models (Zhang et al. 2017). However, similar to natural joints, it became evident that the lubrication with synovial fluid (SF) affects the biotribological behavior and the complex interplay between the SF hydrodynamics and rheology in combination with elastic deformations of the bearing surfaces have to be taken into account (Nečas et al. 2021a, b;Gao et al. 2022). This is usually referred to as elastohydrodynamic lubrication (EHL). ...
... This is usually referred to as elastohydrodynamic lubrication (EHL). Mattei et al. (2011), Nečas et al. (2021a and Gao et al. (2022) recently reviewed numerical analyses of hip and knee replacements. Various methods have been developed to solve and couple the system of equations consisting of the Reynolds equation representing the hydrodynamic pressure build-up, the elasticity, the lubricant gap, and the load balance equations. ...
Fundamental knowledge about in vivo kinematics and contact conditions at the articulating interfaces of total knee replacements are essential for predicting and optimizing their behavior and durability. However, the prevailing motions and contact stresses in total knee replacements cannot be precisely determined using conventional in vivo measurement methods. In silico modeling, in turn, allows for a prediction of the loads, velocities, deformations, stress, and lubrication conditions across the scales during gait. Within the scope of this paper, we therefore combine musculoskeletal modeling with tribo-contact modeling. In the first step, we compute contact forces and sliding velocities by means of inverse dynamics approach and force-dependent kinematic solver based upon experimental gait data, revealing contact forces during healthy/physiological gait of young subjects. In a second step, the derived data are employed as input data for an elastohydrodynamic model based upon the finite element method full-system approach taking into account elastic deformation, the synovial fluid's hydrodynamics as well as mixed lubrication to predict and discuss the subject-specific pressure and lubrication conditions.
The issue of lubrication in metallic artificial hip joints is discussed to prevent the two bearing surfaces from contacting each other. This study aims to analyse the characteristics of elastohydrodynamic lubrication (EHL) and investigate the effect of radial clearance and head size on the tribological performance of metallic artificial hip joints under steady-state conditions using the Fluid-Structure-Interaction (FSI) method. The average load in the z-direction and flexion-extension motion around the y-axis were used to represent normal walking. This study demonstrates that the film thickness profile from the validation study aligns with the findings of the previous study. The contour of the fluid pressure in the central contact zone changes with different time steps – the direction of fluid movement corresponds to the solid-fluid reaction. Additionally, the deformation of the cup surfaces contributes to the continuous fluid film that separates the contact surfaces. Furthermore, design parameters also influence EHL performance. It has been discovered that less radial clearance and a larger head size led to an increase in fluid film thickness.
By using surface piezoelectricity theory, this article investigates the elastohydrodynamic lubrication (EHL) line contact of a transversely isotropic piezoelectric half-plane with consideration of the surface effect under a rigid cylindrical punch. The surface effect in the surface piezoelectricity theory is mainly described by the following parameters: surface piezoelectric constant, surface dielectric constant, surface elastic constant, and residual surface stress. The punch is treated as the electrical insulator. The lubricant, whose viscosity and density are dependent on fluid pressure, is chosen as non-Newtonian fluid. Firstly, by analyzing the frictionless dry contact of piezoelectric materials with surface effect, dry contact pressure distribution and EHL film thickness equation are obtained. Then, an iterative method is proposed to get fluid pressure and film thickness at lubricant contact region by calculating the fluid-solid coupled nonlinear equations. Effects of surface dielectric constant, surface piezoelectric constant, surface elastic constant, residual surface stress, punch radius, entraining velocity, and slide/roll ratio on the film thickness and fluid pressure are examined. Our analysis indicates that surface effect has an essential effect on the EHL contact behaviors of piezoelectric materials at micro-/nano-scales.
