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The 100% Medicare database (2005–2010) was used to evaluate the risk of complication, revision total hip arthroplasty (THA), and cancer for primary THA patients. A matched cohort analysis was performed for metal-on-polyethylene (MoP), metal-on-metal (MoM), ceramic-on-polyethylene (CoP), and ceramic-on-ceramic (CoC) patients, matched by age, gender, and census region. Multivariate Cox regression models were used to compare the risk of dislocation, periprosthetic joint infection, mechanical loosening, mechanical complications, revision THA, and cancer (bladder, kidney, and liver), adjusting for patient and hospital factors. The MoM cohort (n=55 141) was associated with a 15% higher adjusted risk of infection (p=0.003) and 13% higher adjusted risk of loosening (p=0.031), but 11% lower adjusted risk of dislocation (p=0.004) than the MoP cohort (n=165 423). The CoC cohort (n=5527) were associated with a 32% lower adjusted risk of infection (p=0.021) and 40% lower adjusted risk of loosening (p=0.008) than the MoM cohort (n=16 581). The MoM cohort had a 30% lower adjusted risk of kidney cancer relative to the MoP cohort (p=0.021). There were no other significant differences in complications, revision THA, or cancer risk between MoM and the other bearing cohorts. With up to a 5.25-yr follow-up, revision risk did not vary significantly among Medicare THA patient cohorts with different bearing types; in contrast with recent revision data from the U.K. and Australian registries after a similar time period. The higher infection risk for the MoM Medicare cohort may represent local soft tissue reactions that were misdiagnosed as infection. This study describing the outcomes for a large patient cohort with MoM bearings in a national sample of the elderly patient population will be useful in the development of standards and the design of future post-market surveillance studies. The 2005–2010 Medicare dataset does not demonstrate an elevated risk of bladder, kidney, or liver cancer for patients implanted with a MoM bearing.
metal-on-metal, THA, MOM, revision, metal-on-polyethylene, MOP, complications, cancer, Medicare
Ong, Kevin L.
Senior Managing Engineer, Exponent, Inc., Philadelphia, PA
Senior Managing Scientist, Exponent, Inc., Menlo Park, CA
Kurtz, Steven M.
Corporate Vice President and Principal, Exponent, Inc., Menlo Park, CA