Zimmer Knee Failure
According to one recent non-peer reviewed report based on 108 patients with Zimmer NexGen CR-Flex knee implants, the model may be prone to early knee failure as a result of an alleged flaw in the design of the device.
The 2010 report, “The High Failure Rate of a High-Flex Total Knee Arthroplasty Design,” conducted by renowned Chicago orthopedist Richard Berger and Dr. Della Valle of Rush University Medical Center, found that 8.3% of the 108 patients studied underwent revision surgery due to femoral loosening and pain. One percent of the group had an impending revision, and 36% of the group experienced loosening of the devices as evidenced by radiographic evaluation.
The report concluded with a recommendation that further clinical studies be conducted before any new designs are implemented.
Zimmer NexGen CR-Flex Knees’ fixation failure
At the center of the device’s alleged flaw is an aspect that is designed to make it an upgrade over older models by allowing patients to enjoy a wide range of knee motion. The Zimmer NexGen CR-Flex Porous Femoral implant attaches to the femur without the use of fixative or cement, eliminating the risk of cement polluting nearby tissue or entering the bloodstream.
For those who experience failure of the device, the cement-less knee replacement eliminates one risk while creating another. The femoral component of the device, which is coated with a porous liner designed to encourage bone growth or “osseointegration,” fails to keep the femur in place. The problem is exacerbated as pressure is applied to the femoral component when the knee bends, pushing the device out of place and disrupting bone growth.
The problem is not cement-less knees in general. Many porous designs have high rates of osseointegration and low rates of revision.
NexGen CR-Flex remains commercially available
The report presented at the 2010 annual meeting of the American Academy of Orthopaedic Surgeons (AAOS) clearly states, “This component is still commercially available but should not be used for any patient.”
However, the high-flex models remains on the market and Zimmer stands firmly behind the product.