A new study calls for better and more modern ways to evaluate patients before total knee replacement surgery. Under current guidelines, many patients may be receiving the procedure when it could be avoided.

A new study finds that about one-third of total knee replacement surgeries performed in the U.S. are not appropriate according to international guidelines. The study authors hope to see better patient selection criteria in the future to make sure that those going under the knife really need the procedure.

The study was published yesterday in Arthritis & Rheumatology.

According to the Agency for Healthcare Research and Quality, Americans undergo about 600,000 knee replacements each year. Between 1991 and 2010, Medicare-covered knee replacements skyrocketed by about 162 percent per year. Some experts say the procedure is popular because it’s so effective, while others say the surgery is overused.

Daniel Riddle, Ph.D., a professor in the department of physical therapy at Virginia Commonwealth University in Richmond, Va., examined the criteria used to determine whether or not a total knee replacement is appropriate for a particular patient. He believes his study is the first in the U.S. to compare validated criteria for appropriateness to actual cases of knee replacement surgery.

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Riddle’s team focused on real-world scenarios, taking into account a patient’s symptoms, age, and knee mobility and stability, as well as the location and extent of the person’s arthritis. They looked at a modified version of the appropriateness guidelines, which were developed by researchers in Spain, in addition to the commonly used Western Ontario and McMaster Universities Arthritis Index (WOMAC) scale.

The researchers examined data from a five-year study in which 175 people had total knee replacements. About 60 percent of the patients were female, and the average age of knee replacement patients in the study was 67.

The team classified the 175 procedures as either appropriate, inconclusive, or inappropriate. Their assessment showed that 44 percent of the surgeries were appropriate, 22 percent were inconclusive, and 34 percent were inappropriate.

“Our finding that one-third of knee replacements were inappropriate was higher than expected and linked to variation in knee pain osteoarthritis severity and functional loss. These data highlight the need to develop patient selection criteria in the U.S.,” Riddle said in a press statement.

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Dr. Jeffrey Katz, director of the Orthopedic and Arthritis Center for Outcomes Research at Brigham and Women’s Hospital in Boston, Mass., said he believes doctors should be concerned about offering knee replacements to patients that do not meet criteria on the WOMAC pain and function scales.

“The Riddle study used 1999 criteria, and I think these are not suitable for judging the appropriateness of 2010 [and newer] cases,” Katz said. “But we don’t have a contemporary set of criteria. If we did, the authors would have used them.”

Dr. Steven F. Harwin, chief of adult reconstruction and total joint replacement at Mount Sinai Beth Israel medical center in New York, said he performs more than 500 hip and knee replacements each year.

Though the authors used a modified version of a well-established standard (the WOMAC scale), he said he was “surprised” to find that such a high percentage of patients who underwent the procedure were deemed inappropriate candidates.

“Regardless of the instrument used, it is intuitive that if the patient answers ‘none or mild’ on all items relating to pain and function, the surgeon should re-evaluate his indication for surgery,” he said. “In my practice, the typical patient indicated for joint replacement of either the hip or knee has an average pain score of over seven out of 10, and 90 percent have functional limitations that include walking, standing, and bending.”

He said there is no question that the number of joint replacement procedures has gone up. Among other reasons, the implants are quite reliable and baby boomers want to maintain an active lifestyle.

“We must remember that the primary indication for joint replacement is loss of quality of life,” he said. “Once a patient tells us they cannot enjoy their activities of daily living or any recreational activities, to me that puts the indication for joint replacement into the ‘appropriate’ category.”

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