Elastohydrodynamic lubrication analysis of UHMWPE hip joint replacements

Jalali-Vahid, D.; Jagatia, M; Jin, Zhi; Dowson, D.

doi:10.1016/s0167-8922(00)80137-6

Cited by 20 publications

(31 citation statements)

References 15 publications

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“…There have been theoretical and experimental studies that demonstrate that a reduction in radial clearance would result in improved fluid-film lubrication. 20,34,35 Hence, it would be expected that the hard-on-hard bearings would experience improved lubrication with the reduced clearance and the smooth bearing surfaces compared with the hard-on-soft bearings. Nevertheless, a resultant mixed lubrication is still dominant, as evidenced by the level of the measured friction coefficients.…”

Section: Discussionmentioning

confidence: 99%

Friction of total hip replacements with different bearings and loading conditions

et al. 2006

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Metal-on-ultra-high molecular weight polyethylene (UHMWPE) total hip replacements have been the most popular and clinically successful implants to date. However, it is well documented that the wear debris from these prostheses contributes to osteolysis and ultimate failure of the prosthesis, hence alternative materials have been sought. A range of 28 mm diameter bearings were investigated using a hip friction simulator, including conventional material combinations such as metal-on-UHWMPE, ceramic-on-ceramic (CoC), and metal-on-metal (MoM), as well as novel ceramic-on-metal (CoM) pairings. Studies were performed under different swing-phase load and lubricant conditions. The friction factors were lowest in the ceramic bearings, with the CoC bearing having the lowest friction factor in all conditions. CoM bearings also had low friction factors compared with MoM, and the trends were similar to CoC bearings for all test conditions. Increasing swing phase load was shown to cause an increase in friction factor in all tests. Increased serum concentration resulted in increased friction factor in all material combinations, except MoM, where increased serum concentration produced a significant reduction in friction factor.

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Section: Discussionmentioning

confidence: 99%

Friction of total hip replacements with different bearings and loading conditions

et al. 2006

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“…The main governing equations for the present lubrication model are the Reynolds equation, which governs the fluidfilm lubrication between the two bearing surfaces, and the elasticity equation as summarized below [17].…”

Section: Elastohydrodynamic Lubrication Modelmentioning

confidence: 99%

“…The Reynolds equation was discretized using the half-point finite difference scheme for the left-hand terms, and the backward difference scheme for the right-hand term in order to balance the accuracy and stability of the numerical method [7]. The details of the numerical procedure have been given in a previous study by the present authors [17]. The parameters given in Table 1 were chosen for the lubrication analysis, in order to cover a wide range of operating conditions and to enable general film thickness formulae to be fitted.…”

Section: Elasticity Equationmentioning

confidence: 99%

“…There are only a few studies reported in the literature where the elastic deformation of the bearing surfaces was considered in the lubrication analysis [13] and most of these studies are only concerned with the squeezefilm motion [14][15][16]. The effect of entraining action has been recently considered by Jalali-Vahid et al [17] in the development of an EHL analysis and a successful numerical procedure based upon the Newton -Raphson method has been developed for ball-in-socket UHMWPE hip joint replacements. The specific objectives of this study were:…”

Section: Introductionmentioning

confidence: 99%

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Prediction of lubricating film thickness in a ball-in-socket model with a soft lining representing human natural and artificial hip joints

Jalali-Vahid

Jagatia

Jin

et al. 2001

Proceedings of the Institution of Mechanical Engineers, Part J:

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A simple ball-in-socket model was adopted in this study to analyse the lubrication problem of both natural hip joints and their artificial replacements. A compliant layered bearing surface was considered to represent articular cartilage as found in the natural synovial joint and also in the artificial hip replacement where an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup was employed. The cup was assumed to be stationary while the ball was assumed to rotate at a steady angular velocity and under a constant load. A successful numerical method developed in a previous study by the present authors was used to solve the Reynolds equation in spherical coordinates, simultaneously in conjunction with the corresponding elasticity equation based upon the constrained column model. Numerical solutions thus obtained enabled general formulae to be fitted for both the minimum film thickness and the central film thickness, based upon the prediction from the equivalent ball-on-plane model and the half-contact angle. These formulae were then applied to predict the lubricating film thickness in both natural hip joints and their artificial replacements.

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“…The elastohydrodynamic lubrication analysis for a ball-onplane model with a layered bearing surface firmly bonded to a rigid backing was considered by Yao [27] and Dowson and Yao [28,29] using the constrained column model and by Jin [30] in which a full elasticity model was adopted. Jalali-Vahid et al [13] simultaneously solved the Reynolds equation and an elasticity equation based on the column model in spherical coordinates. Subsequently, a parametric analysis of lubricating film thickness was carried out by Jalali-Vahid et al [31,32] and a relatively constant minimum film thickness of 0.15 -0.25 mm was predicted, based on a relatively high angular velocity of 2 rad/s and a viscosity of 0.01 Pa s, despite a wide range of design parameters such as the head radius, radial clearance, cup wall thickness, and UHMWPE elastic modulus.…”

Section: Steady-state Elastohydrodynamic Lubrication Analysismentioning

confidence: 99%

Theoretical studies of elastohydrodynamic lubrication of artificial hip joints

Zhang

2006

Proceedings of the Institution of Mechanical Engineers, Part J:

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Theoretical studies of fluid-film lubrication in artificial hip joints are reviewed. The importance of developing effective numerical tools to solve realistic and complex lubrication problems in artificial hip joints has been emphasized. The elastic deformation of the bearing surfaces has been shown to play a dominant role in promoting elastohydrodynamic lubrication in various forms of artificial hip joints using different bearing surfaces. Both the bearing geometry and the structural supports can have a significant effect on the predicted lubricant film thickness. The importance of elastic deformation is further enhanced synergistically with the transient variation in load and speed to ensure a maximum effectiveness of the transient elastohydrodynamic lubrication mechanism in artificial hip joints. The recent application of the fast Fourier transform technique, in conjunction with the finite-element method to calculate the elastic deformation, not only enables more complex structural supports to the acetabular cup to be considered, but also offers the potential of analysing both transient and mixed lubrication problems in artificial hip joints.

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Elastohydrodynamic lubrication analysis of UHMWPE hip joint replacements

Cited by 20 publications

References 15 publications

Friction of total hip replacements with different bearings and loading conditions

Friction of total hip replacements with different bearings and loading conditions

Prediction of lubricating film thickness in a ball-in-socket model with a soft lining representing human natural and artificial hip joints

Theoretical studies of elastohydrodynamic lubrication of artificial hip joints

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