Australian Study Questions Effectiveness of DePuy Hip System

Posted by PKSD Law Firm on Oct 26, 2010 in Defective Medical Devices

The following is an article that ran in the March 2010 Bioengineering Bulletin from the Department of Medical Engineering and Physics at the Royal Perth Hospital.

Metal-on-Metal Bearings: How Effective?

The increase in use of metal-on-metal (MoM) bearings over the past 5 years has been dramatic. The claimed advantages of low wear and reduced dislocation risk should be balanced against increased metal wear particles. The Australian Joint Registry (2009) identified MoM bearings, in particular ASR (DePuy) and Durom (Zimmer) resurfacings, as having higher than average revision rates. In 2008, the FDA issued a recall on Duron cups because of loosening rates.

Durom and ASR MoM bearings sent for analysis, show high rates of loosening (41%), extensive wear markings on the articular surfaces, and fine corrosion pitting near the rim of the heads. All components are Co-Cr-Mo alloy but differ in composition and manufacturing (cast or forged). Some of the microstructures revealed carbide precipitation at the grain boundaries features that can effect wear and mechanical performance.

Some questions remain:

  • What is the cause of fine corrosion pitting on the bearing surfaces despite excellent in vitro corrosion?
  • What is the relationship between metal hypersensitivity, osteolysis and implant failure (loosening, infection)?
  • Is there a correlation with increased reporting of pseudotumors or ALVAL with usage of MoM bearings?
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