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30-03-2017 | Rheumatology | News | Article

Knee replacement practice in OA patients questioned

medwireNews: Results of a study published in The BMJ suggest that total knee replacement (TKR) has “minimal effects” on quality of life among patients with knee osteoarthritis (OA), and restricting surgery to those with more severe disease would improve cost-effectiveness of the procedure in the USA.

In an analysis of data from 4498 patients included in the Osteoarthritis Initiative (OAI), Bart Ferket (Icahn School of Medicine at Mount Sinai, New York, USA) and fellow researchers identified “small absolute changes” in quality of life (QoL) measures following TKR.

When variables including demographics, history of knee surgery, use of pain medication, and body mass index were taken into account, the team estimated that the physical component summary (PCS) scores of the generic Short Form (SF)-12 survey improved by 1.70 points when averaged over 8 years following TKR, and health-related SF-6D utility scores increased by 0.008 points.

For OA-specific QoL measures, the Western Ontario and McMaster Universities arthritis index (WOMAC) improved by 10.69 points and the knee injury and osteoarthritis outcome score (KOOS) by 9.16 points following TKR.

When the team analyzed QoL measures by baseline physical health, the effect of TKR on SF-6D scores increased with each unit decrease in SF-12 PCS, suggesting that “total knee replacement would become more effective if it was restricted to patients with SF-12 PCS scores <50.”

They then modeled scenarios based on current practice – defined as TKR practice as performed in the OAI – and scenarios restricting surgery to those with severe OA, and found that limiting TKR to patients with SF-12 PCS scores of less than 35 would decrease the lifetime likelihood of TKR from 39.9% to 10.2% and save US$ 6974 per patient compared with current practice, while the number of quality-adjusted life–years would only be “slightly lower,” with a reduction of 0.008 years.

The models showed that current practice is “more expensive and in some cases even less effective” than scenarios limiting TKR to those with lower physical function at baseline.

TKR “could be considered cost effective if the procedure were restricted to patients with more severely affected functional status,” say the researchers.

Ferket and colleagues validated their findings using data from 2907 participants of the Multicenter Osteoarthritis Study (MOST). The simulation yielded “similar” cost-effectiveness results, but restricting surgery to patients with SF-12 PCS scores of less than 40 was identified as the optimal scenario.

The team cautions, however, that the patient populations included in the OAI and MOST studies “might not be representative of the current total population of patients with knee osteoarthritis,” which could limit the generalizability of their findings.

Looking to the future, they call for “more research comparing total knee replacement with less expensive, more conservative interventions, particularly in patients with less severe symptoms, and research aiming to develop individualized prediction models for a better selection of patients with a predicted large net benefit from the procedure.”

By Claire Barnard

medwireNews is an independent medical news service provided by Springer Healthcare. © 2017 Springer Healthcare part of the Springer Nature group