According to a paper presented at the American Association for Hip and Knee Surgeons (AAHKS) 2008 annual meeting, orthopaedists should expect substantial increases in the demand for total joint replacement (TJR) surgery among younger patients in the near future.

Lead investigator Steven M. Kurtz, PhD, reported that by 2030, most of the anticipated demand for primary total hip arthroplasty (THA) procedures as well as primary and revision total knee arthroplasty (TKA) procedures will come from patients younger than 65 years.

“Improving implant reliability and survivorship will be critical in light of the current and anticipated demand for TJR procedures from patients younger than age 65,” said Dr. Kurtz.

In addition, Dr. Kurtz said that the trend may affect physician reimbursement.

“The findings are expected to have implications in the private coverage and reimbursement of TJR procedures in the future,” said Dr. Kurtz. “Patients younger than 65 years are not typically covered by Medicare, which today funds the majority of TJR procedures in the United States. So, this raises questions about potential problems related to funding for these procedures in the future.”

The next 10 years
Dr. Kurtz and his colleagues projected that more than 50 per­cent of the demand for primary total hip arthroplasty (THA) will come from patients younger than 65 years by 2011. In that same year, researchers project that patients younger than 65 years will comprise more than 50 percent of the candidate population for revision total knee arthroplasty (TKA).

By 2016, more than half of primary TKA patients will be younger than age 65. Demand for this procedure is expected to grow the fastest among patients in the 45–54 age category. Researchers anticipate a 17-fold increase in the number of TKAs in this age group—from 59,077 procedures in 2006 to 994,104 procedures by 2030. The demand for primary THA in the same age category is projected to grow nearly 6-fold from 2006–2030.

“Our projections are based on the historical growth trajectory of joint replacement surgeries,” emphasized Dr. Kurtz. “They do not take into account potential limitations in the availability of surgeons or limited economic resources of private and public payors and hospitals in the future.” Both factors could affect the total number of procedures performed.

Calculating national projections for TJR
Dr. Kurtz and his colleagues used ICD-9-CM codes to identify primary and revision arthroplasty surgeries performed between 1993 and 2006 as recorded in the Nationwide Inpatient Sample (NIS), an annual, statistically valid survey of approximately 1,000 hospitals conducted by the Federal Heathcare Cost and Utilization Project. The researchers calculated the prevalence of primary THA, revision THA, primary TKA and revision TKA as a function of age, gender, race, and census region using data on the size of each subgroup as determined by the Census Bureau in 1990 and 2000 as well as intra-census estimates.

Data on the future size of each population subgroup were based on population projections reported by the Census Bureau.

“National TJR projections were obtained by summing the projections for each subgroup, for which both the population and the prevalence of surgery were modeled to vary over time using Poisson regression,” explained Dr. Kurtz. “Independent models were used for primary and revision hip and knee arthroplasty.”

Because the historical surgery rates may not necessarily predict future demand, Dr. Kurtz and his colleagues also created a more conservative set of projections in which the future prevalence of the procedures was fixed at the average performed between 2004 and 2006, according to the NIS data. The results of both sets of projections are summarized in Tables 1 and 2.

Dr. Kurtz serves as a part-time research professor and director of the Implant Research Center at Drexel University’s School of Biomedical Engineering, Science, and Health Systems.

Co-authors—Michael P. Kelly, MD; and Kevin J. Bozic, MD, MBA—are with the Department of Orthopaedic Surgery and Institute for Health Policy Studies at the University of California at San Francisco.

The authors report the following disclosures: Dr. Kurtz—Medtronic, Synthes, Johnson & Johnson, Stryker, DePuy Spine, Archus Orthopaedics, Zimmer, Biomet, DePuy, A Johnson & Johnson Company, Encore Medical, Exactech, Inc, National Institutes of Health; Kyphon Inc.; Dr. Bozic—Integrated Health Care Association; Dr. Kelly reports no conflicts.

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org