Zimmer sells the NexGen Flex uncemented knee implants. These Zimmer uncemented knees fail early in 9% of the patients studied.

Most of these Zimmer protheses have been cleared for use by the FDA but have not undergone any testing in patients. As a result, no one knows what will happen to the patients until it is too late and many patients have to have another operation to remove the defective implants.

On june 20, 2010, an article in the New York Times discused the recurrent problems Zimmer Corporation has had with the failures of their orthopedic implants. Dr. Richard Berger,  noted orthopedic surgeon from Chicago,Illinois, has been designing surgical instruments and artificial joints for Zimmer for over a decade. Zimmer had Dr.Berger train other Orthopedic Surgeons at seminars and conferences in how to proroperly implant their joint protheses.

When Dr. Berger noticed that one of the Zimmer knee protheses he had been using was failing at a much earlier rate than other knee implants, he told Zimmer the problem. He explained the component creats excess pressure which prevents the thigh bone (femur) from fully fusing with the implant. Instead of cooperating with Dr. Berger to determine the cause of the problem, Zimmer abruptly quit working with Dr. Berger and told him that the problem was his technique not the implant. When Dr. Berger learned another Orthopedic Surgeon, who was also a Zimmer consultant, was haing the same problems with the knee implants, they presented their study at the American Association of Orthopedic Surgeons national meeting in 2009.

Their results showed that 9% of the knees were failing too early, (normally, knee implants should last 15-20 years), and there was evidence of loosening in HALF of all the patients with the NexGen CR Flex uncemented knees. 

Two years ago in a similar incedent, another one of the top Zimmer consultants, Larry Dorr, complained of problems he was having with the Zimmer Durom acetabular cup used in hip implants. He had been one of the developers of the implant and had also taught hundreds of other Orthopedic Surgeons how to preform the procedure. When he informed Zimmer of the problems, Zimmertold Dr. Dorr it was not their implant but it was his technique that was at fault.