Zimmer, based in Warsaw, Ind., has since launched a new knee system called Persona and informed its investors that the NexGen litigation holds so little merit that it hasn't bothered to estimate potential losses.
“We believe the plaintiffs' allegations are not consistent with the record of clinical success for these products,” the company disclosed to investors last year in a Securities and Exchange Commission filing, adding that the first “bellwether” trials for the NexGen lawsuits are expected in 2014.
As devicemakers such as Zimmer continue marketing newer and more expensive products, critics say there may be good reason to be skeptical about new techniques and equipment in a quickly evolving product market. The absence of a comprehensive national device registry used in countries such as Australia, Sweden and the United Kingdom makes identifying faulty devices difficult.
“That some of these implants have failed is just not all that surprising, because it's new technology,” said Dr. Mathias Bostrom, a researcher and orthopedic surgeon at the Hospital for Special Surgery, New York, which is part of the New York-Presbyterian Healthcare System.
“As long as you introduce new technology, there is going to be a failure rate,” said Bostrom, who is also a paid consultant for competing devicemaker Smith & Nephew. “You may argue whether it was introduced to the public too soon, and that's a valid discussion that you could have.”
In court records and public statements, Zimmer officials have argued that the NexGen system is actually more reliable than other devicemakers' comparable systems for total-knee replacements, and they say registries in other countries support their contention.
In Sweden, a 2010 study found that Zimmer's NexGen was used in 14,440 patients who were found to be at 0.5% risk of having a revision surgery—the lowest rate for a widely used total-knee device in the registry. In England and Wales, the NexGen system occupied a middle-of-the-pack position, with its 29,730 devices showing a 1.9% revision rate after three years.
“NexGen knees record the best or among the best survivorship rates in national joint replacement registries from around the world,” the company says on zimmerfacts.com, a website devoted to rebutting allegations from the product-safety lawyers.
Dr. Richard Berger, formerly a paid Zimmer consultant who helped develop “minimally invasive” surgical techniques for NexGen systems, publicly criticized some NexGen components for having what he said was an unusually high failure rate—claims that prompted Sen. Chuck Grassley (R-Iowa) to pen a 2010 letter to Zimmer CEO David Dvorak demanding answers.
It was not clear whether Zimmer ever responded to the senator's letter, as neither the company nor Grassley's office would comment for this story.
But it can't be disputed that the NexGen system has experienced problems since its launch.
In September 2010, the FDA issued a medium-severity Class 2 recall for the surgical institutions for 68,384 NexGen MIS tibial components, which are one of the three types of equipment at issue in the ongoing product liability case. The MIS tibia included a shorter bone-stem that was designed to allow smaller surgical incisions, but 114 patients filed FDA complaints saying the device came loose and required revision surgery.
In March 2012, the ECRI Institute sent a High Priority Medical Device Alert to thousands of hospitals worldwide warning that certain NexGen tibia and femur components were causing failures because surgeons were using incompatible plastic articulating plates to separate the bone-mounted ends of the device.
And in January, Mayo Clinic researchers published findings in the journal Clinical Orthopaedics and Related Research that said a NexGen component called the LPS 3-degree tibial tray was failing at an unexpectedly high rate because the cement used to secure the device was “debonding” from the metal device. Mayo has since stopped using that particular tibial component.
“That is a relatively uncommon cause of failure in the short term,” said Dr. Mark Pagnano, professor of orthopedic surgery at Mayo and one of the study authors. “It was a little bit surprising and that is why we reported that. But to keep it in perspective, the vast majority of these knee replacements are still working well at five years.”
Pagnano noted that Mayo doctors were able to investigate the finding using Mayo's internal registry of orthopedic devices implanted in patients. Other health systems have similar internal registries, and in February 2012 a not-for-profit called the American Joint Replacement Registry hired a company to build a national registry with the goal of enrolling 90% of U.S. hospitals by 2016. About 160 hospitals participate today.
Such a database may one day help physicians and patients learn how much risk is inherent in using new technology, versus losing out on the benefits of cutting-edge science—a conflict highlighted by the NexGen litigation.
“There is always incomplete information available,” Pagnano said.
Follow Joe Carlson on Twitter: @MHJCarlson
