Determination of Lubricating Film Thickness for Permeable Hydrogel and Non-Permeable Polyurethane Layers Bonded to a Rigid Substrate with Articular Reference to Cushion form Hip Joint Replacements

1996 ◽  
Vol 210 (2) ◽  
pp. 89-93 ◽  
Author(s):  
G McClure ◽  
Z M Jin ◽  
J Fisher ◽  
B J Tighe
Keyword(s):  
Film Thickness ◽  
Hip Joint ◽  
Squeeze Film ◽  
Glycerol Solution ◽  
Polyurethane Elastomers ◽  
Joint Replacements ◽  
Lubricating Film ◽  
Theoretical Predictions ◽  
Hip Joint Replacements ◽  
Lubricating Film Thickness

The lubricating film thickness in a model of compliant layered bearings, using both permeable hydrogels and non-permeable polyurethane elastomers for total hip joint replacements, has been measured using optical interferometry, under both entraining and squeeze-film motion. The film thickness in the lubricated contact was measured for both water and a 40 per cent glycerol solution in water as a function of entraining velocity and squeeze-film time. The measured lubricating film thickness for the permeable hydrogel was compared to that of the non-permeable polyurethane elastomer and little difference was found when the lubricating film thickness was sufficiently large (greater than 150 nm). Comparison of the experimental results and the theoretical predictions based upon elastohydrodynamic lubrication analysis showed good agreement in the entraining experiments where the film thickness was greater than 150 nm. In the squeeze-film experiments the experimental measurements were greater than the theoretical predictions for all squeeze times due to the formation of a central pocket of fluid which was not predicted by the simple theory used. This also occurred for the hydrogels for films greater than 150 nm. For longer squeeze times the film thickness for the hydrogel fell below the theoretical prediction. This was considered to be due to the permeability of the hydrogel reducing the film thickness when the film thickness was less than 150 nm. The permeability of the hydrogel was not modelled in the theoretical lubrication analysis used in this study.

Prediction of lubricating film thickness in UHMWPE hip joint replacements

2001 ◽  
Vol 34 (2) ◽  
pp. 261-266 ◽  
Author(s):  
D. Jalali-Vahid ◽  
M. Jagatia ◽  
Z.M. Jin ◽  
D. Dowson
Keyword(s):  
Film Thickness ◽  
Hip Joint ◽  
Joint Replacements ◽  
Lubricating Film ◽  
Hip Joint Replacements ◽  
Lubricating Film Thickness

MAPPING OF LUBRICATING FILM THICKNESS IN HUMAN HIP JOINT REPLACEMENTS

2012 ◽  
Vol 2012 (04) ◽  
pp. 378-381 ◽  
Author(s):  
Dalibor Bosak ◽  
Jan Lastuvka ◽  
Martin Vrbka ◽  
Tomas Navrat ◽  
Martin Hartl ◽  
...  
Keyword(s):  
Film Thickness ◽  
Hip Joint ◽  
Joint Replacements ◽  
Lubricating Film ◽  
Hip Joint Replacements ◽  
Lubricating Film Thickness

A full numerical analysis of hydrodynamic lubrication in artificial hip joint replacements constructed from hard materials

1999 ◽  
Vol 213 (4) ◽  
pp. 355-370 ◽  
Author(s):  
Z. M. Jin ◽  
D Dowson
Keyword(s):  
Film Thickness ◽  
Hip Joint ◽  
Hydrodynamic Lubrication ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Acetabular Cup ◽  
Joint Replacements ◽  
Lubricating Film ◽  
Metal On Metal ◽  
Hip Joint Replacements

A full numerical analysis of the hydrodynamic lubrication problem of artificial hip joint replacements with surfaces of high elastic modulus materials, such as metal-on-metal or ceramic-on-ceramic, under cyclic walking conditions is reported in this paper. The Reynolds equation in spherical coordinates has been solved for both entraining and combined entraining and squeeze film motions under a three-dimensional variation in both the load and the speed experienced in hip joints during walking. It has been shown that a finite lubricating film thickness can be developed during the walking cycle owing to the combined action of the squeeze film and entraining motions under some conditions. It has been found that the design parameters for plain spherical bearings, such as the femoral head radius and the radial clearance between the femoral head and the acetabular cup, have a large effect on the magnitude of the predicted lubricating film thickness. Some interest has been shown in recent years in the performance of metal-on-metal bearings in which a dimple has been machined at the pole of the acetabular cup. It is shown that a dimple on the acetabular cup can significantly increase the film thickness throughout the walking cycle, particularly for relatively large depths and if the location of the dimple coincides with the direction of the resultant force acting on the joints. It is concluded that there is a good possibility that a full continuous hydrodynamic lubricating film can be developed in ceramic-on-ceramic hip joint replacements, and perhaps for some well-finished metal-on-metal implants with a relatively small radial clearance. For some metal-on-metal configurations, the effect of elastic deformation of the bearing surfaces must be taken into account in the lubrication analysis, particularly for a relatively large radial clearance.

Measurement of Lubricating Film Thickness in Low Elastic Modulus Lined Bearings, with Particular Reference to Models of Cushion Form Bearings for Total Joint Replacements: Part 2: Squeeze-Film Motion

1994 ◽  
Vol 208 (3) ◽  
pp. 213-217 ◽  
Author(s):  
Z M Jin ◽  
G McClure ◽  
D Dowson ◽  
J Fisher ◽  
B Jobbins
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Thick Layer ◽  
Squeeze Film ◽  
Synovial Joint ◽  
Joint Replacements ◽  
Total Joint Replacements ◽  
Lubricating Film ◽  
Low Elastic Modulus ◽  
Theoretical Predictions

An optical interferometry technique has been successfully used to study the lubricant film thickness in a compliant layered bearing model for total joint replacements under squeeze-film motion. Experiments have been carried out for both thin and thick layers of compliant bearing material. It has been demonstrated that the film thickness patterns depend significantly upon the layer thickness if other parameters are kept constant. For the thin layer, the film thickness in the contact region was found to be essentially uniform and quite good agreement was found with the theoretical predictions based upon a simplified analysis due to Dowson et al. (13) and Higginson (14). However, for the thick layer, a central dimple or pocket was formed and a relatively large difference was found between the experimentally determined central film thickness and the simple parallel circular disc theoretical predictions. The practical implications of the present results are discussed in relation to the lubrication mechanism in the natural synovial joint and its replacement.

Elastohydrodynamic lubrication analysis of ultra-high molecular weight polyethylene hip joint replacements under squeeze-film motion

2001 ◽  
Vol 215 (2) ◽  
pp. 141-151 ◽  
Author(s):  
M Jagatia ◽  
D Jalali-Vahid ◽  
Z M Jin
Keyword(s):  
Molecular Weight ◽  
Femoral Head ◽  
Film Thickness ◽  
Hip Joint ◽  
Elastohydrodynamic Lubrication ◽  
Squeeze Film ◽  
Acetabular Cup ◽  
Joint Replacements ◽  
Hip Joint Replacements ◽  
Ultra High Molecular Weight

Elastohydrodynamic lubrication was analysed under squeeze-film or normal approach motion for artificial hip joint replacements consisting of an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup and a metallic or ceramic femoral head. A simple ball-in-socket configuration was adopted to represent the hip prosthesis for the lubrication analysis. Both the Reynolds equation and the elasticity equations were solved simultaneously for the lubricant film thickness and hydrodynamic pressure distribution as a function of the squeeze-film time was solved using the Newton-Raphson method. The elastic deformation of the UHMWPE cup was calculated by both the finite element method and a simple equation based upon the constrained column model. Good agreement of the predicted film thickness and pressure distribution was found between these two methods. A simple analytical method based upon the Grubin -Ertel-type approximation developed by Higginson in 1978 [1] was also applied to the present squeeze-film lubrication problem. The predicted squeeze-film thickness from this simple method was found to be remarkably close to that from the full numerical solution. The main design parameters were the femoral head radius, the radial clearance between the femoral head and the acetabular cup, and the thickness and elastic modulus for the UHMWPE cup; the effects of these parameters on the squeeze-film thickness generated in current hip prostheses were investigated.

Measurement of Lubricating Film Thickness in Low Elastic Modulus Lined Bearings, with Particular Reference to Models of Cushion Form Bearings for Total Joint Replacements: Part 1: Steady State Entraining Motion

1994 ◽  
Vol 208 (3) ◽  
pp. 207-212 ◽  
Author(s):  
Z M Jin ◽  
D Dowson ◽  
J Fisher ◽  
D Rimmer ◽  
R Wilkinson ◽  
...  
Keyword(s):  
Film Thickness ◽  
Glass Plate ◽  
Elastohydrodynamic Lubrication ◽  
Normal Incidence ◽  
Joint Replacements ◽  
Total Joint Replacements ◽  
Silicone Fluid ◽  
Lubricating Film ◽  
Theoretical Predictions ◽  
Lubricating Film Thickness

The lubricating film thickness in a model of compliant layered bearings for total joint replacements has been measured by means of optical interferometry under entraining motion. The essential features of the present interferometry technique were off-normal incidence light, a combination of polyurethane elastomer and a crown glass plate as bearing surfaces and the use of silicone fluid or water as lubricants. The film thickness in the lubricated contact was measured for both water and silicone fluid under a range of entraining velocities. Reasonable agreement was found between the experimental measurements of the lubricating film thickness and the theoretical predictions based upon elastohydrodynamic lubrication analysis.

Analysis of fluid film lubrication in artificial hip joint replacements with surfaces of high elastic modulus

1997 ◽  
Vol 211 (3) ◽  
pp. 247-256 ◽  
Author(s):  
Z M Jin ◽  
D Dowson ◽  
J Fisher
Keyword(s):  
Hip Joint ◽  
Radial Clearance ◽  
Joint Replacements ◽  
Lubricating Film ◽  
Artificial Hip Joint ◽  
Artificial Hip ◽  
Hip Joint Replacements ◽  
Film Lubrication ◽  
Fluid Film Lubrication ◽  
Lubricating Film Thickness

Lubrication mechanisms and contact mechanics have been analysed for total hip joint replacements made from hard bearing surfaces such as metal-on-metal and ceramic-on-ceramic. A similar analysis for ultra-high molecular weight polyethylene (UHMWPE) against a hard bearing surface has also been carried out and used as a reference. The most important factor influencing the predicted lubricating film thickness has been found to be the radial clearance between the ball and the socket. Full fluid film lubrication may be achieved in these hard/hard bearings provided that the surface finish of the bearing surface and the radial clearance are chosen correctly and maintained. Furthermore, there is a close relation between the predicted contact half width and the predicted lubricating film thickness. Therefore, it is important to analyse the contact mechanics in artificial hip joint replacements. Practical considerations of manufacturing these bearing surfaces have also been discussed.

Transient elastohydrodynamic lubrication analysis of ultra-high molecular weight polyethylene hip joint replacements

2001 ◽  
Vol 216 (4) ◽  
pp. 409-420 ◽  
Author(s):  
D Jalali-Vahid ◽  
Z M Jin
Keyword(s):  
Hip Joint ◽  
Numerical Procedure ◽  
Elastohydrodynamic Lubrication ◽  
Squeeze Film ◽  
Joint Replacements ◽  
Artificial Hip Joint ◽  
Artificial Hip ◽  
Minimum Film Thickness ◽  
Hip Joint Replacements ◽  
Ultra High Molecular Weight

The cyclic variation in both the load and speed experienced during walking was considered in an elastohydrodynamic lubrication (EHL) analysis for artificial hip joint replacements in this study. A general numerical procedure was developed to take both the entraining and squeeze-film actions into the solution of the Reynolds equation in the spherical ball-in-socket coordinate, simultaneously with the elasticity equation, using the Newton-Raphson method. The numerical procedure developed was then applied to an example of hip joint replacements employing an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup against either a metallic or ceramic femoral head under simplified cyclic load and speed conditions. The predicted minimum film thickness was found to stay remarkably constant, despite a large change in the angular velocity and the load. This was attributed to the combined effect of entraining and squeeze-film actions in generating, replenishing and maintaining the lubricating film in artificial hip joint replacements. Furthermore, it was pointed out that the average transient minimum film thickness predicted throughout one cycle was very close to that under quasi-static conditions based upon the average angular velocity and load.

Prediction of transient lubricating film thickness in knee prostheses with compliant layers

1998 ◽  
Vol 212 (3) ◽  
pp. 157-164 ◽  
Author(s):  
Z M Jin ◽  
D Dowson ◽  
J Fisher ◽  
N Ohtsuki ◽  
T Murakami ◽  
...  
Keyword(s):  
Knee Joint ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Contact Radius ◽  
Knee Prostheses ◽  
Stroke Length ◽  
Additional Advantage ◽  
Lubricating Film ◽  
Theoretical Predictions ◽  
Lubricating Film Thickness

The transient lubricating film thickness in knee prostheses using compliant layers has been predicted under simulated walking conditions based upon the elastohydrodynamic lubrication theory. Qualitative agreement has been found between the present theoretical predictions and the experimental measurements using an electric resistance technique reported earlier. It has been shown that the contact geometry plays an important role in the generation of fluid film lubrication in knee prostheses using compliant layers. The maximum lubricating film thickness is predicted for the maximized contact area of a transverse conjunction where the semi-minor contact radius lies in the direction of entraining. The additional advantage of the transverse contact conjunction is that the possibility of lubricant starvation due to small stroke length can be minimized. All these factors, together with the kinematic requirements in the natural knee joint, should be taken into consideration when designing artificial knee joint replacements.

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