Total knee replacement (TKR) for knee osteoarthritis provides the greatest improvement in quality of life in patients with more severe functional impairment, while the procedure produces only minimal improvement in patients with less severe impairment. In addition, performing TKR surgery only in patients with severe symptoms may be cost-effective. These study results were published in the BMJ.

Osteoarthritis of the knee, an important cause of disability, is prevalent in 12% of adults in the United States. Today, more than 640,000 TKR surgeries are being performed each year in the United States, a number that has doubled since 2000. Economically speaking, this translates into $10 billion dollars in healthcare spending every year.

The number of TKR surgeries has increased due to the inclusion of patients with less severe physical function. Until recently, data demonstrating significant benefits associated with TKR surgery applied more to patients with severe symptoms and did not reflect the contemporary surgical population.

Bart S. Ferket, MD, PhD, from the Icahn School of Medicine at Mount Sinai in New York, and colleagues evaluated the effectiveness of TKR surgery for knee osteoarthritis by comparing outcomes in patients who underwent surgery with outcomes in patients who did not in a cohort study.


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Data from 4498 patients with or at high risk for knee osteoarthritis were obtained from a longitudinal cohort known as the Osteoarthritis Initiative (OAI) database. The validation cohort used data from 2907 patients from the Multicenter Osteoarthritis Study (MOST).

Although TKR surgery improved the scores of several quality of life measures, such as the SF-12 physical component summary (PCS), the degree of absolute improvement was small. However, benefits from surgery increased with greater impairment of physical function at baseline.

Performing TKR surgery in patients with more severe symptoms may be cost-effective as well. Reserving surgery for patients with the most disabling quality of life scores (ie, SF-12 PCS <35) could save $7000 per patient with minimal loss of treatment effectiveness for the overall cohort. These findings were replicated in the MOST validation cohort.

Summary and Clinical Applicability

The number of TKR surgeries for knee osteoarthritis has grown significantly over the last few years, largely due to the expansion of eligibility in patients with less severe symptoms. However, the benefits of TKR surgery in this population, which includes less-impaired patients, is unclear. Researchers found that TKR surgery for knee osteoarthritis provided greater benefit and cost-savings when performed in patients with more severe physical functioning.

“Not all patients with knee osteoarthritis are expected to benefit from total knee replacement to the same extent,” Dr Ferket told Rheumatology Advisor. “For practicing clinicians, it would therefore be important to discuss with the patient what the chance is of having a relevant improvement of symptoms (relevant from the patient’s perspective) in the context of a potential adverse outcome. Ideally, also the costs to the healthcare system and society should be considered by physicians in the decision-making.”

“However, our study was not designed to provide answers for individual patients,” he added. “Patients may value outcomes of joint replacement very differently and the decision to undergo surgery should be made taking into account the patient’s preferences. More research should be done on developing and validating tools that can be used to guide the discussion about treatment between the clinician and the patient.”

Limitations and Disclosures

  • The study population from the OAI and MOST cohorts may have included more younger patients compared with the population with knee osteoarthritis in the United States, so the results of this study may not be generalizable 
  • The cohorts did not capture the severity of symptoms right before TKR surgery; thus, symptoms that had worsened immediately before surgery would not have been measured, possibly diluting the observed effect of surgery

Disclosures

The OAI was partially funded by Merck Research Laboratories, Novartis Pharmaceuticals Corporation, GlaxoSmithKline, and Pfizer. 

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Reference

Ferket BS, Feldman Z, Zhou J, Oei EH, Bierma-Zeinstra SM, Mazumdar M. Impact of total knee replacement practice: cost effectiveness analysis of data from the Osteoarthritis Initiative. BMJ. 2017;356:j1131. doi:1110.1136/bmj.j1131