NEW ORLEANS—More than 7 million Americans are living with an artificial knee (4.7 million) or hip (2.5 million), which may have significant future implications in terms of the need for ongoing patient care, according to new research presented at the 2014 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS). Two related studies also found a growing incidence of adults younger than age 65 undergoing total knee replacement (TKR) and total hip replacement (THR) surgeries, and a potential underutilization of these procedures in some segments of the population.
While numerous studies have quantified the incidence rate of TKR and THR in the United States, there is very little information about the number of patients actually living with a prosthetic knee or hip. In a presentation titled “Prevalence of Total Hip (THA) and Total Knee (TKA) Arthroplasty in the United States,” researchers reviewed THR and TKR incidence rates, mortality rates, and relative mortality rates (the difference in survival between THR and TKR patients and the general population) over a 40-year period to estimate 2010 prevalence rates according to age, sex, and time since surgery.
Among the study findings:
• Approximately 0.8% of Americans are living with a hip replacement and 1.5% with a knee replacement.
• More women are living with prosthetic hips and knees than men.
• Prevalence of THR and TKR among adults age 50 and older is as high as 2.3% and 4.6%, respectively.
• The prevalence of THR rises to nearly 6% by 80 years of age. The prevalence of TKR rises to nearly 10% by 80 years of age.
• The states with the highest number of THR and TKR patients are California, Florida, and Texas; the two states with the lowest numbers are Alaska and Hawaii.
“This study shows that around 7 million Americans have a hip or knee replacement,” said Daniel Berry, MD, Professor of Orthopaedics at Mayo Clinic and the senior author of the study. “This large number highlights how these operations have kept a substantial part of our population mobile despite severe arthritis, something that wouldn’t have been possible before these technologies were available. These relatively high prevalence estimates also highlight the significant ongoing need to care for all of the patients with total hip and knee replacement. These prevalence estimates are within the same ballpark as coronary heart disease, and much higher than heart failure or stroke. To put these numbers in perspective, there are roughly one and a half times as many people living with a hip or knee replacement in the US as people living with heart failure.”
Individuals with total hip and knee replacement often are complex patients with multiple chronic conditions,” added William A. Jiranek, MD, Professor of Orthopaedics at Virginia Commonwealth University School of Medicine. “They all need continuing medical attention and some need further surgical attention over the years of having a replacement. As “there are no guidelines to define long-term management of these individuals … our prevalence estimates are vital to agencies charged with planning for the provision of health care services.”
In two related studies presented at the annual meeting—“Trends in Total Hip Arthroplasty in the United States: The Shift to a Younger Demographic” and “Trends in Total Knee Arthroplasty in the United States: Understanding the Shift to a Younger Demographic”—researchers conducted a retrospective review of 2000 to 2009 hospital discharge data on TKR and THR patients from the Nationwide Inpatient Sample (NIS) Healthcare Cost and Utilization Project (HCUP). Researchers looked at procedural rates, gender, race, age, payer type, length of stay (LOS), discharge disposition, and revision burden for each year, stratified by age. US National Census data was used to calculate rates for each procedure per 100,000 US populations within each age group.
Among the study findings:
• The incidence of TKR increased by 120% from 2000 to 2009: 188% for patients ages 45 to 64, and 89% for patients ages 65 to 84. The incidence of THR increased 73% from 2000 to 2009: 123% for patients ages 45 to 64, and 54% for ages 65 to 84.
• The number of revision total knee replacement (RTKR) procedures increased 133%, and the number of revision total hip replacement (RTHR) procedures by 27%.
• The increase in TKR and THR patients is primarily due to “the disproportionate growth in the rate of utilization among younger patients, and secondarily by overall population growth.”
• Medicare was the primary payer for 63.3% of all TKRs and 58.2% of THRs in 2000, and 54.7% of TKRs and 52.8% of THRs in 2009.