Zimmer NexGen CR-Flex Knee Replacement
- Knee Information
- Knee Replacements
- NexGen CR-Flex Knee
- NexGen LPS Flex Knee
- NexGen Knee Recall
- NexGen Knee Lawsuit
- MIS Tibial Component
- Hip Information
- Hip Replacements
- Zimmer Durom Cup
- Hip Lawsuit
Zimmer Manufacturing Company develops, manufactures and markets medical implants and other devices to the tune of more than $4 billion in annual sales. A spinoff from Bristol-Myers, the company developed a total knee device in 1968 and five years later started selling its first metal-plastic knee prostheses. Since, hips and knees have been a profitable business for Zimmer.
However, the company has experienced difficulties – for varying reasons – with several of its medical products, including the NexGen CR-Flex Knee. Zimmer introduced the NexGen CR-Flex Porous Femoral Component in 2003. It was a variation of the company’s NexGen line and uses a cobalt-chromium-molybdenum alloy coated with a porous liner to cap the thigh bone where it connects with the tibia at the knee.
Unlike traditional knee implants, the NexGen CR-Flex is not attached using fixative or cement. This innovation in total knee replacement, called knee arthroplasty, was created to eliminate the risk of cement polluting nearby tissue, entering the bloodstream or breaking down. The porous liner was designed to encourage bone growth, or osseointegration, rather than cement, to keep the femur in place.
However, what was supposed to eliminate one risk inadvertently may have created another – the loosening of the femoral component because of incomplete fusion.
With any knee replacement there is the risk of “adverse events.” These include:
- Loosening or fracture of the prosthetic knee components.
- Dislocation and/or joint instability of the prosthetic knee.
- Misalignment of the prosthetic knee components.
- Disassembly of the prosthetic knee components.
- Bone fracture or nerve damage.
- Swelling.
- Infection.
- Leg length discrepancies.
- Poor range of motion.
- Pain.
The following complications are also possible:
- Adverse reactions to the materials contained in the prosthetic knee. These reactions may range from an allergic reaction to cancer and/or tumors.
- Debris generated from unavoidable wear of the prosthetic knee may cause bone disintegration (osteolysis) and loosening of the prosthetic knee components.
- Blood clots in one or more veins (venous thromboembolic disease).
- Corrosion of the prosthetic knee components.
FDA and NexGen CR-Flex Knee
Problems with the Zimmer NexGen CR-Flex Knee design actually may have begun before its introduction to the marketplace because of the way the federal Food and Drug Administration (FDA) approves certain medical products and devices.
In most cases, before any item, drug, device, or invention can be sanctioned for employment by doctors, or allowed to be sold, a rigorous series of clinical trials must be completed and reviewed to show the drug or device is safe for use. However, the FDA sometimes gives certain products “Premarket Approval” though its 510(k) process if a manufacturer can show that the product is “substantially equivalent” to another device already on the market.
Thus, the 510(k) process essentially bypasses the need for extensive and conclusive clinical trials which are generally necessary to prove a product’s safety and efficacy. A product that has not been rigorously tested may be found defective only after is has been offered for sale.
In the case of the NexGen CR-Flex Knee, Zimmer contended that the new variation was similar to its traditional NexGen line, which had already been approved by the FDA in 1994. Zimmer did not sell the product that way. The company marketed the CR-Flex as a revolution in knee replacements, by playing up the cemented versus uncemented angle.
Zimmer’s backdoor approval allowed it to sell a new and untested product under the guise of it being no different than its previous models. Since 2003, more than 150,000 patients received NexGen CR-Flex Knee implants. (In 2007, Zimmer also received Premarket Approval for its NexGen LPS-Flex Mobile Knee – another case where a Zimmer knee replacement product did an end run around the clinical trial phase.)
Doctors and Zimmer CR-Flex Knee
While cementless femoral components are not necessarily faulty products, some surgeons experienced difficulties with the Zimmer CR-Flex product. In March 2010, Dr. Richard Berger and Dr. Craig Della Valle from the Rush University Medical Center presented the results of their study, “The High Failure rate of a High-Flex Total Knee Arthroplasty Design,” at a conference of the American Academy of Orthopedic Surgeons. The design in question was the NexGen CR-Flex Knee.
The report noted that 9.3 percent of NexGen CR-Flex Knee implants had either necessitated revision surgery or were scheduled to be revised because of looseness and associated pain. It also showed that another 36 percent of those in the study of 108 patients had a loosening of the porous femoral component, as evidenced by radiographic evaluation, within two years of arthroplasty, and that the “loosening and revision were not related to surgeon, approach or patient type.”
Typically, knee replacements are supposed to last an average of 12-15 years, without needing revision. The doctors concluded that the CR-Flex component, while still commercially available, ought to be withdrawn from the market and “should not be used by any patient.”
What was particularly significant in this challenge of the quality of the Zimmer NexGen CR-Flex Knee was that Berger had been a paid consultant for the Zimmer corporation for many years, earning approximately $8 million over the course of a decade for his services.
By 2005, Berger had implanted 125 patients with the uncemented CR-Flex Knee device, but within one year he was advising Zimmer that X-rays suggested signs of loosening because the porous femoral component was not fusing completely to the bone, as the company had indicated it would. Although patients were able to walk, they were experiencing severe pain.
By 2007, Berger had stopped using the replacement entirely and reported that several other surgeons had also experienced problems with it.
Zimmer stood behind its product, suggesting that any problems were not the result of poor product design, but rather of faulty surgical procedures and techniques utilized by Berger and others who questioned the effectiveness of the implant. In backing up its claims, the company cited the NexGen CR-Flex Porous component’s strong track record of clinical success in Australia.
In a March 2010 Securities and Exchange Commission filing, responding to the Berger/Della Valle study, Zimmer reported details from a 2009 Australian National Joint Replacement Registry report. The company pointed to the report’s documenting that Zimmer’s NexGen cementless components logged the lowest revision rate “of all major TKA systems” being used.
Specifically, the revision rate was 1.7 percent out of 7,100 implant procedures. That rate showed that the TKA “is a safe and effective product when used as indicated in the surgical technique.”
While Zimmer also tried to minimize the damage done to its reputation by claiming that “sales of the NexGen CR-Flex Porous component only represented approximately 2 percent of the company’s knee revenues in 2009,” a June 2010 New York Times article on the contentious dispute between the company and Berger, thrust its public relations problem into the national spotlight. The article caught the attention of Congress.
And it was not the first time that Zimmer had come under the scrutiny of the federal government. In September 2007, four of the nation’s biggest makers of artificial hips and knees, including Zimmer Holdings, were charged with criminal conspiracy to violate anti-kickback laws.
The firms agreed to pay a total of $310 million in penalties to settle federal accusations that they used fake consulting agreements and other tactics to get surgeons to use their products. Zimmer, the market leader, was assessed $169.5 million in fines.
