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Study Assesses Impact of Rheumatoid Arthritis on Joint Replacement Surgery Outcomes

New York—June 12, 2013

Two new studies by researchers at Hospital for Special Surgery have shed light on joint replacement outcomes in patients with rheumatoid arthritis (RA). One study overturns the common belief that RA patients have worse outcomes after a total knee replacement (TKR) than patients who undergo the operation for osteoarthritis. The other study demonstrates that RA patients who undergo a total hip replacement were as likely to have significant improvements in function and pain as patients with osteoarthritis (OA), even though they did not do as well.

Photo of Dr. Susan M. Goodman The news will be reported at the European League Against Rheumatism (EULAR) annual Congress of Rheumatology, to be held June 12-15, in Madrid, Spain.

The studies were made possible by the HSS Total Joint Replacement Registry. Started in 2007, this prospective registry includes a gold mine of information including data on all patients who seek care at HSS for knee and hip replacement surgery. “Other hospitals have registries, but what we have is an incredible volume of information on patients that allows us to do interesting studies, because there are so many patients having hip and knee replacement surgeries at our hospital,” said Susan Goodman, M.D., lead author of both studies and a rheumatologist at Hospital for Special Surgery in New York City.

Historically, RA patients have had worse outcomes after joint replacement surgeries, however, whether this was caused by poorly controlled disease or disease treatment was unclear. Starting in the 1980s, effective disease-modifying drugs became available to treat patients with RA. In the late 1990’s, etanercept, infliximab, and other biologic medication came on the market. Today, at HSS over 70% of patients are on  disease modifying drugs and over 50% are on biologics.

In the two new studies, investigators at Special Surgery set out to examine whether outcomes remained worse for RA patients in a cohort with a high prevalence of  potent disease-modifying drugs and biologic agents. Patient pain and function was assessed prior to surgery and two years after surgery using the Western Ontario and McMaster Universities Arthritis Index (WOMAC). This tool measures pain, stiffness, and functional limitation.

Knee Replacement

In one study, investigators used the HSS Total Joint Replacement registry to identify 178 rheumatoid arthritis patients and 5,206 osteoarthritis patients who underwent a TKR. Patients with RA were sicker—while 72% of osteoarthritis patients had no comorbidities, only 34% of rheumatoid arthritis patients fell into this category.

Although TKR patients with RA had worse pain and function prior to surgery compared to controls, these differences disappeared after surgery. “In RA patients, their preoperative scores were significantly worse than the osteoarthritis controls, but in fact our knee replacement patients caught up,” said Dr. Goodman. Patients in both groups had similar satisfaction rates.

Investigators also identified 32 RA patients and 342 OA patients who underwent a TKR revision. In this analysis, they discovered that OA and RA patients had similar pain and function pre-operatively, but patients with rheumatoid arthritis actually had significantly less pain, better function, and were much more satisfied at two years. “Our RA patients undergoing knee replacement revisions did better than our osteoarthritis patients,” said Dr. Goodman.

Hip Replacement
In a second study, HSS investigators compared outcomes of 202 RA patients and 5,810 OA patients who underwent hip replacement. Again, RA patients were sicker—while 80% of osteoarthritis patients had no comorbidities, only 34% of rheumatoid arthritis patients had the luxury of falling into this category.

“When we looked at function using the WOMAC scale, function was significantly worse in the rheumatoid arthritis patients prior to surgery, but interestingly, when we looked at how they did two years down the road, they were as likely to have an improvement in function and pain,” said Dr. Goodman. Almost 100% (RA, 96% and OA, 95%) had a ten point change in score—a ten point change is considered clinically significant. Rheumatoid arthritis patients, however, had worse outcomes. At two years, patients with RA were more likely to have a poor function WOMAC score of 60 or less (18% vs. 4%) and a poor WOMAC pain score of 60 or less (12% vs. 3%). Patients who expected to do well with the surgery had a significantly decreased risk of poor pain and function.

“The rheumatoid arthritis patients have a great response in terms of hip replacement and their hip function improved. Nonetheless, they were a group that did not do as well,” said Dr. Goodman.

Similar findings were identified for patients undergoing hip replacement revision (58 RA patients and 445 OA patients).

“Many RA patients have a worsening or flare of their disease six weeks after surgery,” said Dr. Goodman. “It may be that those patients aren’t able to do their physical therapy because they are not feeling well, and maybe that contributes to poor outcomes down the road.”

Clearly, there is a difference in knee replacement versus hip replacement in patients with RA, but it is unclear exactly what the difference is. “Perhaps the RA patients undergoing hip replacement are delaying their surgery too long. Maybe if we intervene sooner, we would do better functionally,” said Dr. Goodman. The HSS investigators plan to conduct further research to identify possible differences between the two groups.

Both studies were supported by a Centers for Education and Research on Therapeutics grant from the Agency for Healthcare Research and Quality.

Other HSS investigators involved in the hip replacement study are Danielle Ramsden-Stein, M.D., Wei-Ti Huang, M.S., Mark Figgie, M.D., Michael Alexiades, M.D., Lisa Mandl, M.D., MPH, and Rebecca Zhu, B.A. The study will be presented as a poster on Friday, June 14, at 12:30 pm.

Other HSS investigators involved in the knee replacement study include Wei-Ti Huang, M.S., Mark Figgie, M.D., Lisa Mandl, M.D., MPH, and Michael Alexiades, M.D. Both at HSS at the time of the study, Rebecca Zhu, B.A., now at Yale Medical School, and Beverly Johnson, M.D., now at Albert Einstein College of Medicine, were also involved with the research.

This study will be presented on Saturday, June 15, at 10:15 a.m. in a poster session.


About HSS | Hospital for Special Surgery
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 ninth consecutive year) and No. 3 in rheumatology by U.S.News & World Report (2018-2019). Founded in 1863, the Hospital has one of the lowest infection rates in the country and was the first in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center four consecutive times. The global standard total knee replacement was developed at HSS in 1969. 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. In 2017 HSS provided care to 135,000 patients and performed more than 32,000 surgical procedures. People from all 50 U.S. states and 80 countries travelled to receive care at HSS. 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. The HSS Global Innovation Institute was formed in 2016 to realize the potential of new drugs, therapeutics and devices. The culture of innovation is accelerating at HSS as 130 new idea submissions were made to the Global Innovation Institute in 2017 (almost 3x the submissions in 2015). The HSS Education Institute is the world’s leading provider of education on the topic on musculoskeletal health, with its online learning platform offering more than 600 courses to more than 21,000 medical professional members worldwide. Through HSS Global Ventures, 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.


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