Prevalence, Risk Factors and Burden of Osteoarthritis of the Hip

The authors are embarking on a federally funded study of the epidemiology and outcomes of revision total hip replacement in the US Medicare population. This paper reviews background information on the epidemiology and outcomes of revision total hip replacement. Our goal is to identify critical gaps in the published literature on rates and predictors of revision total hip replacement among patients who have had a primary THR. OVERVIEW Osteoarthritis of the hip affects over four million persons in the US and results in over 200,000 primary elective total hip replacements (THR) per year.1-3 Failure of the prosthesis is a costly and disabling complication, resulting in 37,000 revision hip replacements annually in the US.1 At $31,000 per case in hospital costs alone, these revision procedures cost the nation over one billion dollars annually. Revision THR is also potentially morbid, with two-to three-fold higher risks of mortality and major complications than primary THR,4, 5 and less improvement in functional status than primary THR.6, 7 The number of revision and primary THR surgeries performed in the US increased by over 50% from 1993-2004.1 Thus, we can anticipate a growing burden of revision total hip replacements over the next decade, with attendant complications, disability and costs. However, our capacity to anticipate and reduce the number of THR failures is limited by a lack of critical data. Specifically, US population based rates of revision have not been determined and there are no US population based studies of risk factors for THR failure leading to revision. All US studies of THR failures and risk factors associated with failure have been performed in referral centers. There is no national total joint registry in the US and therefore there are no reliable estimates of the annual and cumulative rates and determinants of THR failure in the smaller hospitals that perform the vast majority of THRs in the US.4 As revisions are complex, resource intensive procedures, these data are crucial to ensure adequate care for patients undergoing revision THR and to reduce the risk of failures. These observations highlight the urgent need for population based studies to define the rate of failure leading to revision THR and to identify risk factors, especially those that are modifiable. In this paper, we provide background on the epidemiology and management of osteoarthritis of the hip, including total hip replacement. We describe the utilization rates and outcomes of THR, with emphasis on the key outcome for this proposal -failure of the prosthesis, leading to a revision procedure. We include data on the association between hospital and surgeon volume of THR and outcomes, including failure. The rates, mechanisms and management of THR failure are reviewed. We close by discussing the national total joint registries developed in Scandinavian countries to monitor failure of THR, and preliminary efforts in this country to mount such registries. PREVALENCE, RISK FACTORS AND BURDEN OF OSTEOARTHRITIS OF THE HIP Osteoarthritis is the primary indication for 94% of total hip arthroplasties.4 Approximately 30% of adults greater than age 65 in the US have radiographic evidence of hip OA (Kellgren and Lawrence grade 2, 3, or 4), 2, 3 while the prevalence of symptomatic, radiographically-documented hip OA is about 4% in this age group.3 African-Americans appear to have a similar or even slightly higher prevalence of hip OA than whites.3 Age, genetic predisposition in certain families,14 congenital or developmental hip disorders, obesity, occupational exposure to heavy weight-bearing activities (e.g. farming) and jobs with bending and squatting are established risk factors for the development of hip OA.15-18 The direct medical cost attributable to OA in the US exceeds $15 billion per year.19-21 In addition, persons with OA are two to four times more likely than those without OA to retire early, to report reduction in work hours or to be unable to find work due to illness.20 NON-OPERATIVE MANAGEMENT OF OSTEOARTHRITIS The management of hip OA 22 includes non-pharmacologic approaches such as patient education and self-help programs, social support, weight loss (if the patient is obese), assistive devices, and exercises aimed at stretching, quadriceps strengthening and aerobic fitness. Multiple pharmacologic therapies can be used including acetaminophen, topical analgesics, nonsteroidal anti-inflammatory drugs, COX-2 inhibitors, opioid analgesics and injections of corticosteroids or hyaluronic acid. Jeffrey n. kaTz, Md, MSc, JOhn WrighT, Md, elizabeTh a. WrighT, phd, elena lOSina, phd ortHoPaeDic anD artHritis center for outcomes researcH, DePartment of ortHoPaeDic surgery, Division of rHeumatology, immunology anD allergy, brigHam anD women’s HosPital, HarvarD meDical scHool failureS Of TOTal hip replaceMenT: a pOpulaTiOn-baSed perSpecTive