Zimmer NexGen Knee System Injuries Prompt Defect Questions

Although the Zimmer NexGen Knee System was supposed to be revolutionary, some users say the system - or parts of it - are defective. These users have filed product liability lawsuits against the manufacturer.

Zimmer Knee Replacement: How it Works

The Zimmer Knee Replacement, known as the Zimmer NexGen Knee System, is a Total Knee Arthroplasty or TKA system. There are a variety of components that can be included within it and is designed for patients whose knee is no longer functioning the way it should, due to pain or flexion.

The typical knee system includes a femoral component that attaches at the bottom of the thigh bone, a patellar component which attaches the front of the knee cap, and a tibial component which attaches at the top of the tibia bone.

Zimmer NexGen Knee Replacement High Flex Design Problematic

While the Zimmer NexGen Knee Replacement High Flex Design System is intended to provide the patient with a fully functioning knee, a potential problem with this knee system is that it is designed to provide higher flexion than is even ordinarily provided within the natural knee.

Generally speaking, the knee tends to flex anywhere from zero to a range of about 120 to 140 degrees for any given person. Part of the system that's under scrutiny right now is what's called the High-Flex design, where the Zimmer Knees can flex up to 155 degrees.

There's tremendous debate within the scientific community right now, based on a series of data and literature that's come out in the last several years, as to whether or not there's really any added benefit to having a Zimmer Knee Replacement High-Flex System.

Zimmer Replacement Knee: Questions Surrounding Components & Design

At present, there are question marks surrounding several of the Zimmer replacement knee components: the tibial component, the flex knee design, and the cementless knee.

• Tibial Component.The tibial component - or the MIS tibial component - is attached to the top of the shin and was recalled by Zimmer in September 2010 (MIS is a trademark that Zimmer obtained which stands for Minimally Invasive Surgery). The idea was that, through use of this tibial component with a relatively short stem, a surgeon would be able to conduct a more minimally invasive surgery (MIS) that would hopefully allow for smaller scars and faster healing.
• Flex Knee Design.Another component that's under scrutiny is the flex knee design. Zimmer has a variety of flex knee designs; they have a High Flex Knee, an LPS Flex Knee, and it even designed a system that it claims is gender specific to target a woman's anatomy. That's called the Gender Solutions High Flex Knee Design. Zimmer claims that the knee of a woman is built differently than the knee of a man and, therefore, this design takes into account that specific anatomy. All of those flex knee lines - the CR-Flex, the LPS-Flex and the Gender Solutions High-Flex are currently under scrutiny.
• Cementless Knee.There have also been questions about Zimmer's use of what's called a cementless knee. The femoral component used in knee surgery is a U shaped design that fits under the bottom of the femur bone and attaches there. Zimmer came up with a design where the knee could be affixed to the femur with a coating service on the femoral component that would naturally adhere to the bone without the use of cement. However, investigations about whether the cementless design actually works, leads to failure, or is a defective design, are ongoing.

A lot of these issues came to the forefront during the summer of 2010 when the New York Times reported on two physicians, Dr. Berger and Dr. Della Valle, from Rush Hospital in Chicago. Dr. Berger was a former consultant of Zimmer who implanted a number of flex knees. However, Dr. Berger found the flex knees resulted in unacceptable and high rates of failure, and the need for revision for the Zimmer replacement flex knees.

In fact, almost 10 percent of the patients in a study he conducted required a revision and more than 35 percent experienced loosening of the knee which may require future revision. As a result, Dr. Berger concluded that Zimmer's knee system may not provide the benefits intended and probably should not be used. These facts have led to the filing of numerous Zimmer lawsuits against the manufacturer.