An axisymmetric contact model of ultra high molecular weight polyethylene cups against metallic femoral heads for artificial hip joint replacements

1999 ◽  
Vol 213 (4) ◽  
pp. 317-327 ◽  
Author(s):  
Z M Jin ◽  
S M Heng ◽  
H W Ng ◽  
D D Auger
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Hip Joint ◽  
Contact Model ◽  
Joint Replacements ◽  
Artificial Hip Joint ◽  
Artificial Hip ◽  
Femoral Heads ◽  
Hip Joint Replacements ◽  
Ultra High Molecular Weight

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.

A Bipolar Artificial Hip Joint Design for Contact Impingement Reduction

2015 ◽  
Vol 1123 ◽  
pp. 164-168 ◽  
Author(s):  
Eko Saputra ◽  
Iwan Budiwan Anwar ◽  
J. Jamari ◽  
Emile van der Heide
Keyword(s):  
Molecular Weight ◽  
Range Of Motion ◽  
High Molecular Weight ◽  
Internal Rotation ◽  
Hip Joint ◽  
Acetabular Liner ◽  
Free Range ◽  
Artificial Hip Joint ◽  
Artificial Hip ◽  
Ultra High Molecular Weight

The acetabular liner of an artificial hip joint (AHJ) is easily damaged locally in case of impingement, i.e. in case of contact of the liner wall with the stem neck, especially when it is made from relatively soft material such as ultra high molecular weight polyethylene (UHMWPE). Frequent impingement will severely damage the acetabular liner, requiring replacement of the AHJ. The aim of this study is to reduce AHJ impingement for specific combinations of flexion, internal rotation, and adduction of the thigh, by optimizing the design of the AHJ. The presented new design is based on modifying a conventional AHJ into a bipolar version with a higher free range of motion (RoM). Results show that the proposed design is able to prevent impingement for RoM. The latter range of motion corresponds well with the requirements of Shalat.

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.

Comparison of wear of ultra-high molecular weight polyethylene acetabular cups against surface-engineered femoral heads

2008 ◽  
Vol 222 (7) ◽  
pp. 1073-1080 ◽  
Author(s):  
A Galvin ◽  
C Brockett ◽  
S Williams ◽  
P Hatto ◽  
A Burton ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Hip Joint ◽  
Vapour Deposition ◽  
Polyethylene Wear ◽  
Chemical Vapour ◽  
Alumina Ceramic ◽  
Femoral Heads ◽  
Ultra High Molecular Weight ◽  
Hip Joint Simulator

Alumina ceramic heads have been previously shown to reduce polyethylene wear in comparison to cobalt chrome (CoCr) heads in artificial hip joints. However, there are concerns about the brittle nature of ceramics. It is therefore of interest to investigate ceramic-like coatings on metallic heads. The aim of this study was to compare the friction and wear of ultra-high molecular weight polyethylene (UHMWPE) against alumina ceramic, CoCr, and surface-engineered ceramic-like coatings in a friction simulator and a hip joint simulator. All femoral heads tested were 28 mm diameter and included: Biolox™ Forte alumina, CoCr, arc evaporative physical vapour deposition (AEPVD) chromium nitride (CrN) coated CoCr, plasma-assisted chemical vapour deposition (PACVD) amorphous diamond-like carbon (aDLC) coated CoCr, sputter CrN coated CoCr, reactive gas controlled arc (RGCA) AEPVD titanium nitride (TiN) coated CoCr, and Graphit-iC™ coated CoCr. These were articulated against UHMWPE acetabular cups in a friction simulator and a hip joint simulator. Alumina and CoCr gave the lowest wear volumes whereas the sputter coated CrN gave the highest. Alumina also had the lowest friction factor. There was an association between surface parameters and wear. This study indicates that surface topography of surface-engineered femoral heads is more important than friction and wettability in controlling UHMWPE wear.

A general axisymmetric contact mechanics model for layered surfaces, with particular reference to artificial hip joint replacements

2000 ◽  
Vol 214 (5) ◽  
pp. 425-435 ◽  
Author(s):  
Z M Jin
Keyword(s):  
Contact Mechanics ◽  
Hip Joint ◽  
Joint Replacements ◽  
Total Hip ◽  
Mechanics Model ◽  
Artificial Hip Joint ◽  
Metal On Metal ◽  
Artificial Hip ◽  
Hip Joint Replacements ◽  
Joint Prostheses

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.

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.

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