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HSS Study Identifies RA Patients With Worse Outcomes After Hip or Knee Replacement

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 new study by researchers at Hospital for Special Surgery (HSS) in New York City. This study was made available online in October 2019 ahead of publication today in the July issue of 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,” said lead study author Susan Goodman, MD, a rheumatologist at HSS. “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.”

Dr. 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. “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,” said Dr. Goodman.

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 six weeks of surgery, absolute improvement was not different. In multivariable models, baseline DAS28, disease activity, predicted one-year HOOS/KOOS pain and function with each 1 unit increase in DAS28 worsening one-year pain by 2.41 and one-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.

Dr. Goodman explained that patients with RA should anticipate a significant improvement in pain and function if they undertake hip or knee replacement surgery and that clinicians should target patients with higher disease activity for extra attention, such as increased physical therapy. She said 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,” said Dr. Goodman. “It is not like getting a patient with new onset disease into low disease activity or remission; this is much more challenging.”

Dr. Goodman said 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 concluded.

About HSS

HSS is the world’s leading academic medical center focused on musculoskeletal health. At its core is Hospital for Special Surgery, nationally ranked No. 1 in orthopedics (for the 14th consecutive year), No. 2 in rheumatology by U.S. News & World Report (2023-2024), and the best pediatric orthopedic hospital in NY, NJ and CT by U.S. News & World Report “Best Children’s Hospitals” list (2023-2024). In a survey of medical professionals in more than 20 countries by Newsweek, HSS is ranked world #1 in orthopedics for a fourth consecutive year (2023). Founded in 1863, the Hospital has the lowest readmission rates in the nation for orthopedics, and among the lowest infection and complication rates. HSS was the first in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center five consecutive times. An affiliate of Weill Cornell Medical College, HSS has a main campus in New York City and facilities in New Jersey, Connecticut and in the Long Island and Westchester County regions of New York State, as well as in Florida. In addition to patient care, HSS leads the field in research, innovation and education. The HSS Research Institute comprises 20 laboratories and 300 staff members focused on leading the advancement of musculoskeletal health through prevention of degeneration, tissue repair and tissue regeneration. In addition, more than 200 HSS clinical investigators are working to improve patient outcomes through better ways to prevent, diagnose, and treat orthopedic, rheumatic and musculoskeletal diseases. The HSS Innovation Institute works to realize the potential of new drugs, therapeutics and devices. The HSS Education Institute is a trusted leader in advancing musculoskeletal knowledge and research for physicians, nurses, allied health professionals, academic trainees, and consumers in more than 165 countries. The institution is collaborating with medical centers and other organizations to advance the quality and value of musculoskeletal care and to make world-class HSS care more widely accessible nationally and internationally.