When knee osteoarthritis severely impacts quality of life, total knee replacement is a highly cost-effective treatment option, according to a new study supported in part by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). The study also found that when knee replacement is performed at a medical center that does more procedures than others, cost-effectiveness is even greater. The findings were recently published in the Archives of Internal Medicine.

The procedure, in which the damaged joint is surgically replaced by a prosthesis, is a common one for people with debilitating knee osteoarthritis (OA). Each year, some 500,000 knee replacements are performed in the United States. The question, according to study senior author Elena Losina, Ph.D., associate professor of orthopedic surgery at Harvard Medical School and co-director of the Orthopedics and Arthritis Center for Outcomes Research at Brigham and Women's Hospital, is whether the procedure is a good value.

Using a mathematical model they developed to simulate the various outcomes of end-stage knee OA in a Medicare population with and without total knee replacement, Dr. Losina and her colleagues found that the surgery is cost-effective. According to the model, the researchers found that with the procedure patients experienced a functional improvement over the course of their lives resulting in $18,300 per quality-adjusted year of life (QALY), the equivalent of one extra year in perfect health.

The researchers extended their cost-effectiveness analysis to medical centers performing different volumes of knee replacements as a way to better understand how differences in outcomes are translated into cost-effectiveness benefits. Study co-author Jeffrey Katz, M.D., associate professor of medicine and orthopedic surgery at Harvard, had previously found that hospitals with greater case loads achieved better outcomes. The new study shows that if patients have to choose between having the knee replacement procedure in a high-volume or a low-volume hospital, it is more cost-effective to have it in a high-volume hospital. But, adds Dr. Losina, "If there is no choice, and the question is whether to do it anywhere at all, it is better to do it in a lower volume hospital than to continue to have end-stage knee osteoarthritis." Regardless of hospital volume, she says, total knee replacement is a good value for resources spent, and "is more cost-effective than many other medical and surgical treatments we use today."

The investigation's mathematical model used data from several national and population-based studies, including Medicare claims data and a multinational study on patients awaiting knee replacement. The scientists estimated the impact of total knee replacement on quality of life by looking at the differences in life quality six months and one year after surgery with positive differences indicating improvement. Such factors as pain relief, surgical complications and prosthesis failure were considered in the analysis, along with the cost of the surgery itself and other treatment expenses.

"Knee osteoarthritis isn't life-threatening, but it can make life miserable," says Dr. Losina. "Therefore, the aim of treatment is not to add years to life, but to improve its quality."

The study was also supported by an Arthritis Foundation Innovative Research Grant.

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The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at 301-495-4484 or 877-22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.

Losina E et al. Cost-effectiveness of total knee arthroplasty in the United States: patient risk and hospital volume. Arch Intern Med. 2009 June; 169(12):1113-1121.

Source for TKR statistics: HCUPnet. National statistics on all stays: 2005 outcomes by patient and hospital characteristics for ICD-9-CM principal procedure code 81.54 total knee replacement. http://hcupnet.ahrq.gov/HCUPnet.jsp.

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