I’ve written previously about reported Zimmer knee problems. There has already been a recall of the Zimmer NexGen stemmed tibial component and orthopedic surgeons have called for a recall of the Zimmer NexGen CR-Flex artificial knee. The New York Times and other media outlets have covered this story, so the topic is no secret — even Sen. Chuck Grassley has written a letter calling out Zimmer — but there are other more in-depth reports publicly available that explore issues revolving around Zimmer artificial knees. To varying degrees, these reports raise significant questions about the post-operative qualities of life for the patients involved.
In a European Federation of National Associations of Orthopaedics and Traumatology report titled “Are High Flexion Activities after High-Flex Total Knee Replacement Safe?”, researcher examined the factors contributing to what the researchers determined was a “high rate of aseptic loosening in femoral components of LPS-flex TKAs”. The study relied on data obtained from March 2003 to September 2004.
The report’s main conclusion offers mixed results for the Zimmer NexGen LPS-Flex knee replacement: “The high-flex implant allowed for greater range of motion and high-flexion activities, and however, showed high rate of early femoral component loosening, which was associated with weight-bearing high-flexion activities.” This report was authored by S. Kang; K. Sup Yoon; and H. Soo Han, and was published in the Journal of Bone and Joint Surgery – British Volume, Vol 92-B, Issue SUPP_II, 322.
Also published by the Journal of Bone and Joint Surgery, another significant study found that “no clinically relevant or statistically significant improvement was obtained in flexion with the ‘high-flex’ prostheses.” This “meta-analysis” was conducted by R. Mehin, MD, MHSc, FRCSC, Orthopaedic Surgeon; R. S. Burnett, MD, FRCS(C), Dipl ABOS, Orthopaedic Surgeon; and P. M. A. Brasher, PhD, Senior Scientist, and relied on data from the products’ inception to December 2007.
From the Mehin study:
A new generation of knee prostheses has been introduced with the intention of improving post-operative knee flexion. In order to evaluate whether this goal has been achieved we performed a systematic review and meta-analysis. Systematic literature searches were conducted on MEDLINE and EMBASE from their inception to December 2007, and proceedings of scientific meetings were also searched. Only randomised, clinical trials were included in the meta-analysis. The mean difference in the maximum post-operative flexion between the ‘high-flex’ and conventional types of prosthesis was defined as the primary outcome measure. A total of five relevant articles was identified. Analysis of these trials suggested that no clinically relevant or statistically significant improvement was obtained in flexion with the ‘high-flex’ prostheses.
If you’re wondering about just how important flexion is, a third publicly available study was published in the November 2009 edition of Orthopedics. “Range of Flexion After Primary TKA: The Effect of Soft Tissue Release and Implant Design” was authored by Issaq Ahmed, BEng, MBChB, MRCS; Andrew C. Gray, MD, BSc, MBChB, FRCS(T&O); Marietta van der Linden, PhD; Richard Nutton, MD, FRCS, with their goal to present a “randomized, controlled study was to determine which factors are predictive of postoperative range of flexion.”
According to this study, “preoperative and intraoperative flexion are the best predictors of final ROM, regardless of the degree of soft tissue release and implant design.”
Remarkably, the FDA does not typically require artificial joint manufacturers, like Zimmer, to test its products in actual patients before artificial joints are marketed and sold to unsuspecting patients across the country. As more Zimmer knee defects emerge, perhaps increased attention will be focuses on these issues.
If medical device manufacturers won’t do the right thing and the FDA fails to conduct adequate oversight, it is up to the patients and the public ensure accountability. Device manufacturers should perform all testing required to ensure that products they implant into patients is not defective. Defects in devices like artificial hips, knees and other artificial joints hurt people. We need to make sure it stops.
[More on Zimmer NexGen Artificial Knee Problems]
(c) Copyright 2011 Brett A. Emison
Brett Emison is currently a partner at Langdon & Emison, a firm dedicated to helping injured victims across the country from their primary office near Kansas City. Mainly focusing on catastrophic injury and death cases as well as complex mass tort and dangerous drug cases, Mr. Emison often deals with automotive defects, automobile crashes, railroad crossing accidents (train accidents), trucking accidents, dangerous and defective drugs, defective medical devices.
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