Reports indicate performance issues with Zimmer knee implants

Published date : 28 August 2012
Article date : 28 August 2012

In 2003 Zimmer introduced the NexGen CR-Flex knee implants and marketed the device as an improvement over older devices. Instead of providing a femoral component that was cemented to the bone, as was the case in traditional knee replacements, the CR-Flex replaced the cement with a porous liner that would keep the implant in place by encouraging bone growth between its components.

Renowned orthopaedic surgeon and former Zimer Consultant, Dr. Richard Berger, who taught correct surgical technique for high flex NexGen knee replacement procedures, personally implanted several of the CR-Flex devices. When following up on patient progress, however, he discovered that in many cases the femoral component had failed to fuse with the thighbone.

In March 2010, Dr. Berger and his colleague, Dr. Craig Valle, from Rush University Medical Center, reported on a study of 108 patients. The study showed that 36% of the participants suffered from premature loosening of the implant and 8.3% required revision surgery. They recommended that the device should be removed from the market but Zimmer disagreed and responded that the problems were a result of surgical error. Dr. Berger’s contract with Zimmer was not renewed following the publication of the study.

Critics assert that Zimmer failed to discover the potential problems with the Zimmer NexGen line of implants prior to market launch because they failed to conduct clinical trials on the device. Instead, they sought FDA approval through the fast-track 510(k) approval process which requires only that the implant be substantially similar to a product already on the market. As a result, many patients were implanted with NexGen devices that may not have been adequately tested.

A later study, presented on February 9, 2012 to the American Academy of Orthopedic Surgeons, confirmed that the Zimmer NexGen tibial component was linked to higher than expected failure rates. Researchers at the Mayo Clinic reviewed data from over 1,000 patients who went through knee replacements between 2000 and 2011. Complications from the NexGen system were 3.9% and half of those involved premature loosening. Most of the loosening cases were because the tibial component separated from the bone.

Source: Eric Chaffin, New York Times, 22 August 2012 (U.S.)

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