Total Knee Arthoplasty and Zimmer Knee Products
The Zimmer NexGen CR-Flex is one type of device used in a Total Knee Arthroplasty (TKA), a surgery to replace all the components that make up the joint of the knee. A successful TKA can dramatically improve the quality of a patient’s life, restoring mobility, dependence, and pain-free living. However not every TKA is successful. Zimmer knee failure in the NexGen CR-Flex model, for example, has formed the basis of a recent wave of Zimmer knee replacement lawsuits.
TKA: cutting edge of modern medicine
TKA is recommended for patients whose own knees have been damaged by disease or injury. It is one of the most common joint replacement procedures in the United States, and most commonly performed in people between 60 to 80 years of age. TKA is typically performed after all conservative treatment options have been considered and exhausted. This is especially so in younger patients because implants such as the Zimmer NexGen CR-Flex have a limited survival expectancy of about10 to 15 years.
The knee, the largest joint in the body, is made up of the lower end of the thighbone (femur) the upper end of the shin bone (tibia) and the knee cap (patella). There are four large ligaments which attach to the femur and tibia that stabilize the joint known as the posterior (PCL) and anterior (ACL) cruciate ligaments as well as the medial and lateral collateral ligament. The joint surfaces, where the bones touch, is coated with cartilage, a smooth protective substance that cushions the bones enabling them to move easily, and the remaining knee surfaces are covered by a thin tissue liner called the synovial membrane which releases a fluid substance that lubricates the knee reducing friction.
Common causes of knee pain
- Joint inflammation
- Rheumatoid arthritis
- Breakdown of protective cartilage
- Deterioration of synovial membrane
Any of these symptoms may limit knee function and cause significant pain. Many choose to undergo TKA as a remedy. Several replacement devices are available on the market; Zimmer knee components are among the most popular.
Zimmer Knee Failure: Discovery and Debate Regarding CR-Flex Model
The Zimmer NexGen CR-Flex Porous Knee is a cementless device. The metal of the device has special pores that allow natural bone to grow into the implant rather than using a special orthopaedic cement to hold the components in place. However, the CR-Flex has been the subject of controversy after allegations of higher than expected Zimmer knee failures.
Reports on the rate of knee failure were made public by Dr. Richard A. Berger, an orthopedic surgeon at Chicago’s Rush University Medical Center and former Zimmer consultant. The surgeon published a non-peer reviewed study entitled “The High Failure Rate of a High-Flex Total Knee Arthroplasty” that was presented at the 2010 Annual Meeting of the American Academy of Orthopedic Surgeons. According to Dr. Berger, 8.3% of 108 patients who had received a NexGenCR-Flex model experienced Zimmer knee failure and revision surgery within just 5 years of having the original TKA.
While Zimmer vigorously denies this trend, patients nonetheless continue to bring Zimmer lawsuit complaints raising similar claims of knee failure and revision surgery with the NexGen CR-Flex model.
Zimmer Knee recall has not been issued for NexGen CR-Flex
Though there has never been a Zimmer knee recall associated with the NexGen CR-Flex Porous Knee, many surgeons, including Dr. Berger, agree that the devices should not be used. Problems with other models, however, have warranted recalls.
On September 13, 2010 the NexGen Complete Knee Solution MIS Total Knee procedure stemmed tibial component was recalled. Zimmer had received 114 reports of device loosening that required knee revision surgery. To remedy the problem, Zimmer sent an urgent device correction letter to all customers who were instructed to destroy previous versions of the Zimmer knee surgical instructions and to become familiar with new modifications and warnings that were added. Among the warnings were recommendations to fully cement and pressurize the anterior and posterior surfaces of the tibial component and use of a drop down stem extension when performing Zimmer TKA of this device.
On October 21, 2010 the NexGen Complete Knee Solution Stemmed Tibial Component was part of a class 2 recall because of incorrectly positioned or missing flange plugs. The missing plug could lead to either surgery delay or the possibility of wear leading to additional surgery. An urgent market withdrawal was sent to sales and distributers requesting that all products be located and immediately quarantined.
The last Zimmer knee recall was on December 2, 2010 with the class 2 recall of the NexGen Complete Knee Solution LPS Femoral Component and the LPS Flex Gender Femoral Component. The component showed evidence of a nonconforming internal CAM radius, the condition was intermittent and not every device had the dissimilar geometry. An urgent device correction and removal notice was sent out requesting that all products be returned . However, no action for surgeons was required.