In patients with rheumatoid arthritis (RA), higher disease activity — not post-operative flares — increases the risk of pain and poor function one year after a total hip arthroplasty (THA) or total knee arthroplasty (TKA), according to a study by researchers at Hospital for Special Surgery (HSS) in New York City.

The study was published online in October 2019 ahead of its recent publication in Arthritis Care & Research.

“What we found was that at one year, those patients who had active disease were not as likely to do well, but the flares themselves didn’t really contribute to pain or poor function,” says lead study author Susan Goodman, MD, a rheumatologist at HSS, in a media release. “I think this study gives us an idea that in RA, disease activity is really the bad actor when it comes to hip and knee replacement outcomes.”

Goodman and colleagues conducted the study after noticing that patients with RA have outcomes that aren’t consistently as good as patients with osteoarthritis after hip or knee replacement. Most RA patients undergoing THA and TKA have active RA and report post-operative flares, but whether RA disease activity or flares increased the risk of higher pain and lower function scores one year later was unknown. Understanding the reason for poor pain and function scores in RA patients can help optimize postoperative care.

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“One of the things we were suspicious of given the high likelihood of having a flare of RA after hip or knee replacement was that maybe those patients who flared couldn’t complete their physical therapy and wouldn’t be able to advance as quickly, leading to worse outcomes,” Goodman shares.

To find out, the researchers launched the RA Perioperative Flare Study, a prospective observational cohort study of patients with RA undergoing a THA or TKA at HSS from November 2014 through April 2018. At baseline, the researchers obtained a full set of clinical data on the state of a patient’s disease, assessing the severity and activity of disease.

Patient-reported outcome measures were collected prior to surgery and were repeated at one year and included the Hip and Knee Osteoarthritis/Disability and Injury Outcomes Scores (HOOS/KOOS) and physician assessments of disease characteristics and activity (DAS28, CDAI).

Participants answered a questionnaire each week for six consecutive weeks postoperatively that addressed RA status and whether patients were experiencing a disease flare. The final analysis included 122 patients, 56 undergoing a THA and 66 undergoing a TKA.

The researchers found that although HOOS/KOOS pain was worse for patients who flared within 6 weeks of surgery, absolute improvement was not different. In multivariable models, baseline DAS28, disease activity, predicted 1-year HOOS/KOOS pain and function with each 1 unit increase in DAS28 worsening 1-year pain by 2.41 and 1-year function by 4.96 (P=0.0001). High BMI also increased the risk of worse function. Postoperative flares were not independent risk factors for pain or function scores.

Patients with RA should anticipate a significant improvement in pain and function if they undertake hip or knee replacement surgery and clinicians should target patients with higher disease activity for extra attention, such as increased physical therapy, Goodman explains.

She adds that part of being an optimal candidate for surgery should include having less active disease.

“One of the problems we have found is that many patients have longstanding active disease and have been on multiple different medications,” Goodman says. “It is not like getting a patient with new onset disease into low disease activity or remission; this is much more challenging.”

Goodman adds that for patients with uncommon and challenging diseases, such as lupus and RA, it is important to seek care in a center that specializes in treating patients with these conditions.

“That is one of the clearest ways to optimize your outcomes,” she advises.

[Source(s): Hospital for Special Surgery, PR Newswire]