News Release 

Prosthetic joint infections missed in patients with rheumatic diseases

Hospital for Special Surgery

Standard diagnostic methods are not adequate to identify prosthetic joint infections (PJIs) in patients with rheumatic diseases, according to findings from a new study by researchers from Hospital for Special Surgery (HSS) in New York City. The study was presented at the American College of Rheumatology/Association of Rheumatology Professionals annual meeting in Atlanta on November 12.

Lead study author Susan M. Goodman, MD, a rheumatologist at HSS, said that while patients with rheumatic diseases are more prone to developing PJIs, it is also harder to make a PJI diagnosis in this population because many of the typical inflammation features of PJIs are similar to those seen in inflammatory arthritis flares. "If a patient with osteoarthritis comes in with a swollen and inflamed prosthetic joint, it is an infection until proven otherwise, but for patients with rheumatoid arthritis, it can be very hard to sort out whether this is part of an overall flare of disease or if it is a true infection," she said. "None of the available tests are that helpful."

The researchers launched the new study to examine the clinical and microbiological features of total hip and total knee arthroplasty PJIs in patients with rheumatic diseases and osteoarthritis. The researchers used the HSS institutional PJI registry to create a retrospective cohort of total hip/total knee replacement PJIs from 2009 to 2016. They identified 807 PJI cases, including 36 in patients with rheumatic disease and 771 in patients with osteoarthritis. Culture-negative cases were defined as PJIs with no evidence of microbial growth in intraoperative cultures; culture-positive PJIs were defined by positive microbial growth.

Among the findings, the researchers discovered that patients with rheumatic diseases had a higher proportion of culture-negative PJIs (27% vs 14%; P=0.02). "Patients with rheumatic diseases who were culture negative were less likely to meet the pathology criteria for infections than the ones who were culture positive, and they did a little worse," said Dr. Goodman. One-year survivorship of culture-negative osteoarthritis and culture-negative rheumatic disease were 87% and 66%, respectively, and 47% for culture-positive rheumatic disease.

"The main message is that patients with rheumatic disease seem to have more culture-negative prosthetic joint infections than patients with osteoarthritis, but what we don't know is what that means in terms of long-term management," said Dr. Goodman. "We had the feeling that we were missing something with our rheumatic disease patients who were coming in with prosthetic joint infections, so I wasn't surprised by our findings, but it pointed out how much more we need to do to really understand this."

Dr. Goodman said the next step is to do a prospective study in patients with rheumatic disease, which will provide the standard diagnostic tests for PJIs but also use Next Generation Sequencing including cell-free DNA methods to better identify bacteria present in tissue.

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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 tenth consecutive year), No. 3 in rheumatology by U.S. News & World Report (2019-2020), and named a leader in pediatric orthopedics by U.S. News & World Report "Best Children's Hospitals" list (2019-2020). 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 addition, HSS will be opening a new facility in Florida in early 2020. In 2018, HSS provided care to 139,000 patients and performed more than 32,000 surgical procedures, and people from all 50 U.S. states and 80 countries travelled to receive care at HSS. There were more than 37,000 pediatric visits to the HSS Lerner Children's Pavilion for treatment by a team of interdisciplinary experts. 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 HSS Education Institute is the world's leading provider of education 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. http://www.hss.edu.

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