Hip Implants More Problematic for Women, Says Study

According to an extensive report published by the Journal of the American Medical Association Internal Medicine, women are more likely to need revision surgery after a hip implant than men. The risk of the implants failing is low, but women were 29 percent more likely than men to need a repeat surgery within the first three years. Researchers looked at more than 35,000 surgeries at 46 hospitals in the Kaiser Permanente health system.

“This is the first step in what has to be a much longer-term research strategy to figure out why women have worse experiences,” said Diana Zuckerman, Ph.D., president of the nonprofit National Research Center for Women & Families. “Research in this area could save billions of dollars,” and prevent patients from experiencing the pain and inconvenience of surgeries to fix hip implants that go wrong.

Zuckerman did note, however, that the results of this study are not likely very consequential. She noted that most patients considering hip replacement are already suffering pain and limited mobility and have few other options. “Knowing that their chances of success are lower than men’s is not helpful to women who are unable to perform many activities of daily living,” she said. The answer, she went on to suggest, would be “long-term comparative effectiveness research based on large sample sizes, indicating which total hip arthroplasty devices are less likely to fail in women and in men, with subgroup analyses based on age and other key patient traits, as well as key surgeon and hospital factors.”

After an average of three years, 2.3 percent of the women and 1.9 percent of the men had undergone revision surgery to fix a problem with the original hip replacement. Problems included instability, infection, broken bones and loosening.

“There is an increased risk of failure in women compared to men,” said lead author Maria Inacio, an epidemiologist at Southern California Permanente Medical Group in San Diego. “This is still a very small number of failures.”

Women tend to have smaller joints and bones than men, and so they tend to need smaller artificial hips. However, it is the larger sizes in women that seem to pose the biggest problem. For femoral head (the ball-shaped part of the joint) sizes of 36 millimeters or more, the adjusted hazard ratio for failure in women versus men was 1.49, whereas differences in revision rates for smaller head sizes were not significant after adjustment.

The study noted that a year ago, the U.S. Food and Drug Administration (FDA) has provided guidance documents to manufacturers for sex-specific analyses in studies of medical devices. However, agency guidance is not a mandate. Even if the FDA were to finalize this requirement, most joint replacements are still classified as moderate-risk devices. As such, these devices are reviewed by the FDA through the 510(k) clearance process and not the pre-market approval process, and therefore rarely undergo clinical trials.