SYMPOSIUM: ABJS CARL T. BRIGHTON WORKSHOP ON HEALTH POLICY ISSUES IN ORTHOPAEDIC SURGERY Future Young Patient Demand for Primary and Revision Joint Replacement

Previous projections of total joint replacement (TJR) volume have not quantified demand for TJR surgery in young patients (\ 65 years old). We developed projections for demand of TJR for the young patient population in the United States. The Nationwide Inpatient Sample was used to identify primary and revision TJRs between 1993 and 2006, as a function of age, gender, race, and census region. Surgery prevalence was modeled using Poisson regression, allowing for different rates for each population subgroup over time. If the historical growth trajectory of joint replacement surgeries continues, demand for primary THA and TKA among patients less than 65 years old was projected to exceed 50% of THA and TKA patients of all ages by 2011 and 2016, respectively. Patients less than 65 years old were projected to exceed 50% of the revision TKA patient population by 2011. This study underscores the major contribution that young patients may play in the future demand for primary and revision TJR surgery. Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence. Introduction The aging of the Baby Boom generation, who will start reaching 65 years old in 2011, is a factor in the increased future demand for joint replacement surgery in the United States. Total hip arthroplasty was originally conceived by Sir John Charnley as a procedure for elderly patients of low activity levels [2]. Over time, the indications for lower extremity joint arthroplasty have expanded to include both younger and more active patients. Indeed, over the past decade, the incidence of total joint replacement (TJR) has increased not only in older ([ 65 years) but also in younger patients (\ 65 years) [7]. The implication of patient age-related differences in future demand for TJR has remained unexplored. Since TJR was primarily intended to treat the elderly patient population, it is unclear if the incidence of these procedures in younger patients would exceed that in older patients in the future. Historically, young patients have been considered at higher risk for revision due to their higher activity level relative to elderly patients [8]. ‘‘Premium’’ implant technologies, such as hard-on-hard bearings and hip resurfacing, have been introduced to address the increased activity and need for improved implant longevity in younger patients. However, these bearings are associated with higher costs and questions regarding their cost-effectiveness for the elderly patient population have been raised [1]. Previous projections by our group focused on estimating the total nationwide demand for primary and revision TJR [6], and not quantified the relative future size of the young TJR population in the United States that may benefit from premium implants. Due to the likelihood that the young patient population will utilize more costly premium bearings, the future size of this patient group could have a substantial impact on the healthcare costs associated with TJR. Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. S. M. Kurtz, E. Lau, K. Ong (&), K. Zhao Exponent, Inc., 3401 Market St, Suite 300, Philadelphia, PA 19104, USA e-mail: kong@exponent.com M. Kelly, K. J. Bozic Department of Orthopaedic Surgery and Institute for Health Policy Studies, University of California, San Francisco, San Francisco, CA, USA 123 Clin Orthop Relat Res (2009) 467:2606–2612 DOI 10.1007/s11999-009-0834-6