Zimmer Knee Failures Zimmer produces various lines of artificial joints including knees. Recently one of its knee products has experienced serious problems. The Zimmer NexGen CR-Flex Porous Femoral knee replacement system attaches to the thigh bone without cement. It relies instead on the bone naturally fusing with the implant. Doctors have reported failures of the NexGen CR-Flex at an unacceptable rate. Within a year of replacement surgery, X-rays of some patients revealed that the device had not fused correctly. These patients could walk but were reporting pain.

Zimmer has rejected the researcher's call for a voluntary recall. It points to the success of the NexGen knee. But the company does not have separate data on the NexGen CR-Flex. Zimmer claims this is because the FDA has not required testing of the knee in patients before selling it.

Dr. Richard Berger and Dr. Craig Della Valle conducted a study of the NexGen knee. In their study the NexGen CR-Flex failed earlier than other artificial knee replacements.

The researchers found that within two years of surgery, 9.3% of NexGen CR-Flex implants had been revised or were scheduled to be. They also found that 36% of these implants showed signs of loosening.

The physicians reached two conclusions:

• The NexGen CR-Flex knee problems were linked to the design of the implant.
• The knee replacement problems were not related to the surgeon, the surgical approach or the type of patient.

The physicians call the failure rate of the NexGen CR-Flex "unacceptably high." About one out of 100 patients needs revision surgery during the first year. After 10 years, the chance of needing more surgery is about 10 percent.

According to the New York Times, Zimmer isn't persuaded by the study. The company cites positive results in a large database of patients in Australia. Zimmer claims that Berger and Della Valle simply implanted the devices incorrectly. However, Zimmer once relied upon Dr. Berger to instruct other physicians on how to implant their devices.