Kaiser Permanente Study: Short-Term Risk of Hip Implant Failure Higher for Women

SAN DIEGO, Calif. — Total hip replacements are more likely to fail for women than for men, according to a Kaiser Permanente Southern California study published today in the journal JAMA Internal Medicine.

The study is one of the largest to compare implant failure rates for women and men following a primary elective total hip replacement procedure, which also known as a total hip arthroplasty. Failure is defined as a revision procedure for any reason, including both septic and aseptic reasons.

By using a Kaiser Permanente joint replacement registry and examining the electronic health records of more than 35,000 patients who received primary elective — planned, non-emergency surgery — total hip replacements between April 1, 2001 and Dec. 31, 2010, researchers found that women were at a 29 percent higher risk of short-term implant failure than men after considering patient, surgical, surgeon, volume and implant-specific risk factors. During the study period, the failure rate for any reason was 2.3 percent for women and 1.9 percent for men. No differences were observed in the risk of failure due to infection-related reasons.

“Patients’ sex has become a pressing issue in orthopedics, particularly given the anatomical differences between males and females, such as the size of the pelvis and acetabulum, or socket and head of the hip joint,” said study lead author Maria C.S. Inacio, epidemiologist with Kaiser Permanente’s Surgical Outcomes and Analysis Unit of Clinical Analysis. “Additionally, because total hip replacements are performed more often in females, it is imperative that we understand the association between implant failure and whether a patient is female or male.”

Researchers also found that regardless of the material used to make the implants and their specific features, women remained at a higher risk of short-term failure than men. This was especially true for metal-on-metal devices, where women had an almost twice greater risk of failure than men. These findings confirm the results of previous studies, which also found metal-on-metal implants are associated with a higher risk of device failure in females.

The authors say anatomical differences between men and women may account for the differing implant failure rates. Specifically, women typically have to be fitted with smaller implants, including a smaller femoral head, due to their smaller size and this may increase the rate of dislocation. Researchers are also looking into the role that bone density may play in implant failure.

“Our study will allow patients to make more informed decisions when discussing hip replacements with their physicians,” said Inacio. “It is important that patients and physicians work together to identify potential risks and customize a care plan best suited for the patient.”

In 2010, Kaiser Permanente added a patient risk calculator to the organization’s electronic health record system. This tool helps physicians estimate the patient’s unique probability of device failure, as well as other risks associated with joint replacements. Examining these risk factors allows the physician and patient to make personalized treatment decisions.

According to the Agency for Healthcare Research and Quality, more than 285,000 total hip replacements are performed each year in the United States. The primary reason people require a total hip replacement is osteoarthritis, a serious and painful joint disease that places severe limits on daily activity and quality of life. Approximately 26 percent of women in the United States were diagnosed with osteoarthritis in 2010, compared to 18 percent of men, according to the Centers for Disease Control and Prevention.

This study was made possible by Kaiser Permanente’s Total Joint Replacement Registry, which now has more than 160,000 total joint arthroplasty procedures registered. Since its inception in 2001, Kaiser Permanente’s registry has helped health care providers identify clinical best practices, evaluate and monitor patient outcomes and risk factors associated with revision surgeries, and assess the clinical effectiveness of implants. Developed in association with Kaiser Permanente’s surgeons, the registry’s data is collected prospectively through standardized documentation by surgeons and supplemented by the organization’s electronic health records.

Kaiser Permanente’s implant registries, which include the Total Joint Replacement Registry, recently won the 2012 annual John M. Eisenberg Patient Safety and Quality Award, sponsored by The National Quality Forum and The Joint Commission. These registries are models of integration across medical centers in nine states and they represent strong partnerships among health plan administration, hospitals and physician medical groups united to improve the quality of care for patients.

This study is part of Kaiser Permanente’s ongoing research on joint implants and patient risk factors that can lead to implant revision. In 2010, a Kaiser Permanente study showed that a detailed and standardized national registry of commonly used joint replacement devices could improve patient outcomes and create clinical and financial efficiencies.

The study analysis was funded in part by the Division of Epidemiology, Office of Surveillance and Biometrics, Center for Devices and Radiological Health in the U.S. Food and Drug Administration.

Other study authors included: Christopher F. Ake, PhD, Elizabeth W. Paxton, and Monti Khatod, MD, of the Southern California Permanente Medical Group; Cunlin Wang, MD, PhD, Thomas P. Gross, MD, MPH, Ronald G. Kaczmarek, MD, MPH, and Danica Marinac-Dabic, MD, PhD, of the U.S. Food and Drug Administration; and Art Sedrakyan, MD, PhD of the Weill Medical College of Cornell University.

About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 9 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: kp.org/newscenter.