SAN DIEGO, Feb. 18, 2013 /PRNewswire/ -- 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.