The reasons for failures of implanted knees have changed over the past 15 years, with the majority of failures today relating to surgeon-dependent factors such as component malpositioning, a researcher stated here.

"Polyethylene wear used to be the main cause of primary knee arthroplasty failure, but poly is now made and sterilized better, with improved articulation and locking mechanisms," explained William Schroer, MD, of the St. Louis Joint Replacement Institute in St. Louis, at the annual meeting of the American Academy of Orthopaedic Surgeons.

The data implicating polyethylene wear as the primary culprit of failure in total knee arthroplasty were from 2001, and are still quoted in current literature and presentations.

Schroer's group collected data from six centers between January 2010 and December 2011. They conducted a retrospective review of why primary knee implants failed in almost 700 cases, and the time frames in which this happened.

During the first 2 years, 243 knee revisions were done. Between years 2 and 5, an additional 172 were done, while 199 occurred between years 5 and 15, and 67 after 15 years.

In 85% of cases they also were able to determine whether the implant was initially successful or was never successful.

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