FRIDAY, Jan. 2, 2009 (HealthDay News) -- Though viewed as a safe and long-lasting way to alleviate hip-related pain, hip-replacement surgery isn't foolproof. And when the procedure fails, the problem more often lies with surgical error than a prosthetic design flaw, a new survey found.
Dislocation of the implant was the most common cause for hip-replacement failure, followed by a loosening of the implant and infections -- such as staph -- that struck either during surgery or later on, the survey said.
"We certainly don't want to give the public the alarming concern that hip-replacement failures are on the rise," said the study's lead author, Dr. Kevin Bozic, an associate professor of orthopedic surgery and health policy at the University of California, San Francisco. "That's not at all what this shows. It's just a single snapshot in time."
"Yet this study is the first to give us information from a very big national database on the cause of failure in a large population, which we didn't previously have," he added. "And what it does suggest is that when hip replacement does fail, the weak link is not the wearing out of the bearing surface, but other problems that in large part are probably related more to the surgical technique used rather than the implant device itself."
Bozic, who's a member of the board of directors of the American Academy of Orthopaedic Surgeons, reported his team's findings in the January issue of The Journal of Bone and Joint Surgery.
The findings could have important ramifications, given that hip replacement is very common in the United States, Bozic said.
"Together with knee-replacement surgery, it's one of the three most common operations," he said. "And the frequency is increasing dramatically because of a number of factors, including an aging population, people having it done at a younger age, and new and improved technology and techniques."
To assess the leading causes of hip-replacement failure, the study authors analyzed a nationwide hospital survey conducted between October 2005 and December 2006. The survey included data on all hip-replacement surgery revisions that were performed after initial hip-surgery failure.
Because the data was the first to be collected under a newly implemented and more detailed diagnostic and procedural coding system for hip replacements, Bozic and his colleagues were better equipped than previous researchers to identify apparent failure trends.
The survey identified more than 51,000 hip-revision surgeries.
Bozic and his colleagues found that the most common cause for the most common type of hip-revision surgery -- known as "total hip arthroplasty" -- was instability or dislocation of the initial hip device, which accounted for approximately 23 percent of cases. "Mechanical loosening" of the device caused nearly 20 percent of the revisions, and another 15 percent was attributed to infection.
"So the message is simple," Bozic said. "We found that there are causes of hip-replacement failure that we hadn't believed were the most common causes but that we now know are significant concerns and should be investigated further."
Dr. Jay Mabrey, chief of orthopedic surgery at Baylor University Medical Center in Dallas, was very enthusiastic about Bozic's study.
"Bozic is a kind of orthopedic genius, and this is a fantastic study," Mabrey said. "It's about time that someone went about proving that technique is more important than the prosthesis itself. It's something that those of us who do a lot of hip and knee replacements have known for quite a while. But no one's ever done anything like this before."
The bottom line, Mabrey said, is that "as a consumer you really should be concerned more with the surgeon who is going to put in the replacement and less concerned with which implant is being put in."
More information
To learn more about hip replacements, visit the U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases.
