Osteoarthritis of the hip affects over four million persons in the US and results in over 200,000 primaryelective total hip replacements (THR) per year. Failure of the prosthesis is costly and disabling, resulting in37,000 revision hip replacements annually in the US. Although increasing evidence points to a growingburden of revision total hip replacements over the next decade - with attendant complications, disability andcosts - US population based rates of THR failure have not been determined. Further, there are no USpopulation based studies of risk factors for THR failure. All data have been reported from referral centers,where a minority of THR's is performed. These observations highlight the urgent need for population-basedstudies of the rate of failure leading to revision THR and to identify risk factors, especially those that aremodifiable. This proposal builds upon the extensive experience of the research team in population-basedstudies of the utilization and outcomes of THR in the US Medicare population. In previous work weassembled a claims-based cohort of 58,000 Medicare beneficiaries who had elective THR between July1995 and June 1996. In this application we propose to follow this cohort for twelve years following the indexTHR to undertake the following specific aims:1) To perform a nested case control study in order to identify factors associated with prosthesisfailure leading to revision following elective primary THR. Risk factors will be ascertained frommedical records, Medicare claims, Census data and American Hospital Association data.2) To estimate the cumulative incidence rate of prosthesis failure leading to revision THR over twelveyears in a national population-based cohort of Medicare beneficiaries, and to identify factorsassociated with prosthesis failure in the national claims cohort.The findings will provide a national estimate of the risk of THR failure and an assessment of factorsassociated with THR failure at a national level. We investigate risk factors at the patient, surgeon andhospital level, permitting inferences that will guide clinical and policy interventions at several levels. Thesedata will permit clinicians to better inform patients about the anticipated longevity of their implants and aboutfactors that may influence prosthesis survival, and consequently the patient's quality of life.Lay Summary: Total hip replacement is done frequently for severe arthritis of the hip. There is very littleinformation available at a national level on how long the implants work properly until they cause pain andneed to be replaced. This study uses information from Medicare claims and medical records to determine therisk of failure of the hip replacement and the factors that predict which patients will experience a failure.
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