Oxidation in Ultrahigh Molecular Weight Polyethylene and Cross-Linked Polyethylene Acetabular Cups Tested against Roughened Femoral Heads in a Hip Joint Simulator

The established biaxial rocking motion (BRM) hip joint simulator was complemented by a novel friction measurement accessory. This simple and practical system, which was easily added to an existing BRM design, is described in detail and shown to perform well in long-term wear tests and in comparative tests of 24 h duration involving several different bearing couples. The system was based on the measurement of frictional torque about the leaning axis of the lower component, the femoral head. In the 28 mm CoCr-on-ultrahigh molecular weight polyethylene articulation with diluted calf serum lubricant at body temperature and 1 kN static load, the maximum value of frictional torque during a cycle was 1.2 N m on the average. The alternative system based on the measurement of torque about the vertical loading axis was shown to be less sensitive and highly insensitive when contact area was small, as was the case with alumina-on-alumina.

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

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1243/09544119jeim407 ◽

2008 ◽

Vol 222 (7) ◽

pp. 1073-1080 ◽

Cited By ~ 27

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.

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