Concerns Mount Over Zimmer NexGen CR-Flex Porous Femoral Component Failures

Evidence is growing that the NexGen CR-Flex Porous Femoral Component device made by Zimmer Inc. may be associated with a substantially higher-than-expected failure rate. Knee replacements should last around 15 years, but evidence suggests that the Zimmer NexGen CR-Flex Porous Femoral Component is prone to fail in three years or less.

Introduced in 2003, Zimmer’s NexGen CR-Flex Porous Femoral Component is a synthetic device used to cap the thigh bone (femur) where it connects with the tibia at the knee. Unlike traditional knee implants, the component is made of a porous fiber metal and a cobalt-chromium-molybdenum alloy and is not attached using cement.

In a filing with the U.S. Securities and Exchange Commission (SEC), Zimmer noted that the NexGen CR-Flex Porous Femoral component was the subject of a study of 108 patients (“The High Failure Rate of a High-Flex Total Knee Arthroplasty Design”) by Drs. Richard Berger and Craig Della Valle of Rush University Medical Center. The Zimmer SEC filing states: “According to the published abstract, Drs. Berger and Della Valle revised 9 (8.3%) patients for femoral loosening and pain. The study also reported that 39 (36%) patients showed evidence of radiographic loosening and that “[l]oosening and revision were not related to surgeon, approach or patient type.”

In their study, which was presented at the March 2010 Annual Meeting of the American Association of Orthopaedic Surgeons, Drs. Berger and Della Valle concluded: “This component is still commercially available but should not be used for any patient,” the study authors wrote.

Incidentally, Zimmer ended its consulting relationship with Dr. Berger shortly after he began criticizing the NexGen CR-Flex Porous Femoral Component . According to a New York Times report, when Dr. Berger initially reported to Zimmer in 2006 that he had to replace the device in some patients, company officials suggested his technique was to blame for the problems. Zimmer claimed that no other surgeons had made similar complaints.

By 2007, Dr. Berger had stopped using the CR-Flex device. According to him, several other surgeons had reported similar problems. That’s when he and Dr. Della Valle decided to conduct their study. Last year, Zimmer chose not give Dr. Berger a new contract.

For his part, Dr. Berger told the Times that he has lost confidence in the company. He is trying out other products, and is considering a consulting relationship with another firm.