Knee replacements cost-effective, say US researchers

Medical Tribune August 2009 SFI
David Brill

Total knee arthroplasty (TKA) is cost-effective, especially when performed in high-volume centers, according to a US study.

The findings will prove valuable for informing both policy and practice as the number of TKAs performed each year continues to spiral upward, the authors say. Some 500,000 TKAs were performed in the US in 2005, at a cost of over US$11 billion, and the number of procedures is projected to reach 3.5 million by 2030.

The study found that the incremental cost-effectiveness ratio of TKA was US$18,300 per quality-adjusted life year (QALY) – a figure that meets most commonly used definitions of cost-effectiveness. The UK National Institute for Health and Clinical Excellence, for example, sets its cost-effectiveness threshold between £20,000 and £30,000 (around US$33,000 to US$49,000) per QALY.

The researchers, led by Dr. Elena Losina of the Brigham and Women’s Hospital, Boston, developed a computer model using Medicare claims data and outcomes data of people with end-stage knee osteoarthritis. [Arch Intern Med 2009 Jun 22;169(12):1113-21]

Quality-adjusted life expectancy increased from 6.8 to 8.0 QALYs in people who underwent TKA. Procedures performed at low-volume centers cost more and were less effective than in high-volume centers, regardless of whether patients were at high or low risk.

TKA is widely accepted as an effective procedure but assessing cost-effectiveness has proven difficult, due in part to the ethical and logistical constraints that prohibit a randomized controlled trial.

Despite the insights from the new study, however, policymakers still face many difficulties in evaluating established medical technologies such as TKA, according to an accompanying editorial by Assistant Professor Stephen Lyman, director of the epidemiology and biostatistics core at Weill Cornell Medical College, New York, and colleagues.

“At least in the US, even well-performed cost-effectiveness analyses do not influence either payers or physicians directly. Payers do not use the results to make coverage determinations nor do physicians use them to make treatment decisions. How we move from this current state to a system in which cost-effectiveness of procedures affects medical practice is unclear,” they wrote. [Arch Intern Med 2009 Jun 22;169(12):1102-3]

Demand for TKAs is also expected to rise in parts of Asia, where populations are ageing rapidly. An analysis of 1,663 procedures from a high-volume center in Singapore found that patients were typically Chinese females in their mid-60s. Ninety six percent had osteoarthritis and four percent had rheumatoid arthritis. [Ann Acad Med Singapore 2008 Nov;37(11):924-8]

Average length of stay decreased between 2000 and 2005 – due, in part, to an increase in the number of same-day admissions. Overall complication rates were 2 percent and mortality less than 1 percent, the group from Tan Tock Seng Hospital reported.