Determination of Low Wear Rates in Metal-On-Metal Hip Joint Replacements Based on Ultra Trace Element Analysis in Simulator Studies

A general axisymmetric contact mechanics model for layered surfaces is considered in this study, with particular reference to artificial hip joint replacements. The indenting surface, which represents the femoral head, was modelled as an elastic solid with or without coating, while the other contacting surface, which represents the acetabular cup, was modelled as a two-layered solid. It is shown that this model is applicable to current total hip joint prostheses employing ultra-high molecular weight polyethylene (UHMWPE) acetabular cups against metallic, metallic with coating or ceramic femoral heads as well as metal-on-metal combinations. The effect of cement is also investigated for these prostheses using this model. The use of a metallic bearing surface bonded to a UHMWPE substrate for acetabular cups is particularly examined for metal-on-metal hip joint replacements. Both the contact radius and the contact pressure distribution are predicted for examples of these total hip joint replacements, under typical conditions. Application of contact mechanics to the design of artificial hip joint replacements employing various material combinations is discussed.

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Simulation: Problems Relating to Mechanical Tests on Hip Joint Replacements

Engineering in Medicine ◽

10.1243/emed_jour_1980_009_005_02 ◽

1980 ◽

Vol 9 (1) ◽

pp. 17-22

Author(s):

A M Gatti

Keyword(s):

Hip Joint ◽

Ceramic Materials ◽

Mechanical Tests ◽

Acetabular Cup ◽

Joint Replacements ◽

Wear And Friction ◽

The Coefficient Of Friction ◽

Low Wear ◽

Hip Joint Replacements ◽

Joint Prostheses

In hip joint prostheses, one of the problems is the choice of mating materials. In fact the coefficient of friction between the cup surface and the surface of the head should be very small in order to minimize any tendency towards loosening related to friction torques on the cup. A low wear coefficient is also desirable to provide maximum life of the acetabular cup. Failures of some types of hip joint prostheses with respect to these parameters induced us to carry out a series of simulation tests. For evaluation of these mating materials as to wear and friction, two different lines of investigation were followed. The work considers two different cases relating to results obtained by several authors. From the analysis of the different hip joint simulators we have concluded that (i) it is not possible to compare results, (ii) there are even non-suitable simulators, and (iii) the few suitable simulators can also be used in order to obtain an improved surface finish (especially for ceramic materials), before the implantation.

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Overview of metal-on-metal hip joint replacements, recognizing the signs and symptoms of failure

Internal Medicine Review ◽

10.18103/imr.v3i7.492 ◽

2017 ◽

Vol 3 (7) ◽

Author(s):

Alexander Rahill

Keyword(s):

Hip Joint ◽

Signs And Symptoms ◽

Joint Replacements ◽

Metal On Metal ◽

Hip Joint Replacements

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

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/0954406991522310 ◽

1999 ◽

Vol 213 (4) ◽

pp. 355-370 ◽

Cited By ~ 51

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.

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