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In 2003 Zimmer, Inc. introduced its NexGen CR-Flex knee implants. Zimmer 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 was supposed to keep the implant in place by encouraging bone growth between its components.

Unfortunately, post-marketing reports seemed to indicate that this plan did not work. In March 2010, renowned orthopedic surgeon and former Zimmer consultant Dr. Richard Berger and his colleague, Dr. Craig Valle, from Rush University Medical Center, reported on a study of 108 patients. The study showed that 36 percent of the participants suffered from premature loosening of the implant. They noted at the time that the device should be removed from the market.

Zimmer disagreed, stating the problems stemmed from surgical error.

NexGen Implants Approved Without Clinical Trials

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.

Consequently, many patients were implanted with NexGen devices that may not have been adequately tested.

Dr. Berger Reports on Zimmer Knee Failures

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.

Concerned, Dr. Berger tamed with Dr. Valle to conduct a study on the implants. Out of 108 patients observed, 8.3 percent required revision surgery, while 36 percent showed signs of premature loosening. Berger concluded that the device had a high risk of failure, and should be withdrawn from the market. Zimmer disagreed, and refused to admit any problems with the implant.

Dr. Berger’s contract with Zimmer was not renewed following the publication of the study.

Mayo Clinic Study Confirms Berger’s Findings

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 20111. Complications from the NexGen system were 3.9 percent, and half of those involved premature loosening. Most of the loosening cases were because the tibial component separated from the bone.

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