A new study has found that certain complications of knee and hip replacement surgery are more common in patients with rheumatoid arthritis (RA) than in patients with osteoarthritis (OA). However, experts note the risks of complications in these common surgeries are still low – and outcomes are generally excellent.

The analysis, which appears in the December 2012 issue of Arthritis & Rheumatism, relied on data from 40 studies on joint replacement surgery published between 1990 and 2011, which contained information about outcomes in both RA and OA patients who had a knee or a hip replaced. The researchers looked at five complications: infection, dislocation of new hip joints, early revision (the need to re-replace a joint because of, for example, the failure of an artificial joint component), blood clots and death.  

The authors found that RA patients had an increased risk for infection after a knee replacement. But the unexpected finding is that RA patients also had an increased risk for hip dislocation after a hip replacement.

“Dislocation following hip replacement means that the femoral component – the implant that goes into the thigh bone – comes out of joint from the acetabular component – the cup,” explains study co-author Bheeshma Ravi, MD, of the University of Toronto Division of Orthopaedic Surgery, in Canada. “We found that patients with RA have a higher risk of this complication, relative to patients with OA.”

Dr. Ravi says this was a surprising finding – and one worthy of further study. “Some potential explanations for this finding may include differences in how surgeons perform joint replacement in patients with RA versus OA, or use of different prostheses,” he says, noting that the “risk for dislocation persisted even after we controlled for these factors.”

Further study might come up with ways to mitigate this risk, Dr. Ravi says, including use of a certain type of implant and changes to the post-operative rehabilitation protocol.