500,000 Americans get new knee each year

U. ROCHESTER (US) — The volume of total knee replacements in the US has soared by 142 percent since 1991 among those receiving Medicare benefits.

The rapid rise in the common and costly elective surgeries is due to patient demand, a higher number of Medicare enrollees, and more osteoarthritis caused by obesity, according to the study published in the Journal of the American Medical Association.

And although the marked growth in total knee replacement (arthroplasty) suggests the procedure is largely safe, successful, and extremely popular among active older adults, the report also notes the high volume could be viewed as a source of strain on the government, insurers, individuals, and businesses struggling with how to contain health care spending.


The report is timely and hints at the complexities of restraining costs within a changing health care environment, says Stephen L. Kates, professor of orthopaedics at the University of Rochester Medical Center, and a co-author of the study.

“We’ve identified a number of interesting trends that we hope will add to the national conversation on health and economic policies,” Kates says. “Knee replacement surgery has become one of the most expensive diagnoses in medicine today because it is growing disproportionately to the population.”

The study involved observation of nearly 3.6 million patients ages 65 and older, who underwent primary and revision knee surgery during the past 20 years, to look for changes in volume, utilization, and outcome.

Per-capita utilization of primary knee surgery jumped 76 percent, and the volume of revision surgery increased 99 percent. Rates of poor outcomes remained stable, but 30-day readmission rates went up slightly (4.2 percent to 5 percent), as did the prevalence of obesity and diabetes.

Another major trend, the study says, is the move toward outpatient rehabilitation and a significant decline in length-of-stays in the hospital. The latter was accompanied, however, by increasing readmission rates in recent years. Among those who had revision surgery, researchers charted a rise in hospital readmissions due to infections.

As middle-aged and older adults attempt to remain pain-free and active for as long as possible, data suggests that approximately 500,000 total knee arthroplasties (TKA) are performed annually in the US—at a cost of about $15,000 per surgery or $9 billion per year.

Because of a lack of a national registry, however, researchers could not investigate whether all or most surgeries are being done appropriately, after following clinical guidelines for managing knee osteoarthritis with medications and physical therapy.

In an editorial accompanying the study, James Slover and Joseph D. Zuckerman of New York University Langone Medical Center focus on the cost issue. They suggest that payment structures may need to change, to bundle the total cost from preoperative care through the recovery period. They also suggest a future system in which high-volume joint replacement centers, which have the experience and infrastructure to keep costs lower, would take the majority of cases.

“It is difficult to determine the extent to which growth in TKA utilization represents growth in appropriate use of a highly effective procedure or overuse of a highly reimbursed procedure,” write the study authors. “It is likely that both factors are at play.”

Kates receives research funding from the Agency for Healthcare Research and Quality, Synthes USA, American Geriatric Society, Orthopaedic Research and Education Foundation, National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the AO Trauma.

Lead author was Peter Cram of the University of Iowa Carver College of Medicine. Yue Li, a policy and outcomes researcher in the department of community and preventive medicine at University of Rochester Medical Center, is also a co-author of the study.

Source: University of Rochester