Which Arthritis Patients Gain From Joint Replacement?

Janis C. Kelly

April 15, 2013

Canadian health services wait-lists for joint arthroplasty are growing longer, but only about half of patients who had a hip or knee replacement reported a significant improvement in pain and mobility after surgery, according to a new study by Gillian A. Hawker, MD, from the Women's College Hospital and the Institute for Clinical and Evaluative Sciences, Toronto, Ontario, Canada, and colleagues. In an article published online March 4 in Arthritis & Rheumatism.

Dr. Hawker and colleagues write that good outcomes were most likely in patients with more severe pain, a single affected joint, few other health problems, and osteoarthritis (OA) rather than inflammatory arthritis.

"While demand for joint replacement surgery has increased as our population ages, physicians lack a set of established criteria to help determine what patients will benefit from surgery and at what point during the course of the disease. As physicians, we need to do a better job of targeting treatments to the right patient at the right time by the right provider," Dr. Hawker said in a press release.

"This is a well-done, timely, important study. There is increasing recognition that we need to target our treatments to patients who will benefit. We need to understand who is most likely to benefit and who is least likely to benefit, so we can choose surgical candidates appropriately. The Hawker study begins that discussion," Peter Cram, MD, MBA, told Medscape Medical News.

Dr. Cram, director of the Division of General Internal Medicine at the University of Iowa Carver College of Medicine, Iowa City, was lead author on a recent study of usage and outcomes of knee replacement procedures among US Medicare patients.

Dr. Cram said, "Typically, older age and more comorbidities predict worse outcomes. These data are consistent with that work. The basic issue is whether we can make a reasonable guess at who will benefit from joint replacement. The answer is that we probably can. Are we doing that?"

Benefit vs Risk

The researchers conducted a population cohort study of 2411 patients with arthritis, using survey data linked to the Canadian Institute for Health Information Discharge Abstract Database, which records all hospital admissions. Of these patients, 479 had total joint replacements, 143 were excluded from the analysis because they had nonelective or revision total joint arthroplasty (TJA), died, or received a second arthroplasty during follow-up. Western Ontario McMaster Universities OA Index (WOMAC) data were available for 202 of the remaining 336 patients (133 knee replacements and 69 hip replacements). Of these patients, more than 85% had more than 1 troublesome hip or knee.

The mean improvement in WOMAC summary score was 10.2 points. The researchers defined "good outcome" as a WOMAC summary score improvement of the minimal important difference of 0.5 SD mean change, which in this case was 9 points, or more. Patient satisfaction with the outcome of TJA was not included in the analysis.

Good outcomes occurred in 53.5% of TJA recipients (51.9% of knee replacements and 56.5% of hip replacements). The best predictive model included 4 variables: preoperative WOMAC summary score, number of troublesome hips/knees, arthritis type, and number of comorbidities.

"[C]ontrolling for other factors, participants with less self-reported pain and disability pre-TJA were less likely [than] those with greater severity to experience a good outcome," the authors write.

"As demand for TJA increases, there is an urgent need to identify patient factors that are associated with high likelihood of experiencing a net clinical benefit, in particular the degree of arthritis severity at which the benefits of TJA are likely to outweigh potential risks," the authors conclude.

"We should be thinking carefully about who we select for joint replacement. Not all patients will benefit equally. In this analysis of 202 Canadian patients there were factors that predicted less improvement. Doing knee replacement on someone with mild symptoms might not be the thing to do. We should probably wait until symptoms become more severe," Dr. Cram said.

Medscape Medical News tried to reach the researchers for comment but was not successful.

The authors and Dr. Cram have disclosed no relevant financial relationships.

Arthritis Rheum. Published online March 4, 2013. Abstract