Medtronic said about 1,000 people have sued the company over its bone morphogenetic protein-2 (BMP-2) product, Infuse, and that many more lawsuits may be coming.
In addition, several states now are looking into sales and marketing practices involving Infuse, which is used in spine surgery.
In a statement, company spokesperson Cindy Resman said the cases are in early procedural stages, and none have resulted in a finding of liability against Medtronic.
Some court rulings have led to dismissals and others have limited claims.
"Medtronic stands behind Infuse bone graft and will vigorously defend it in court," she said.
Richard Deyo, MD, a professor of family medicine at Oregon Health & Science University, who has done research into the use of Infuse in spine surgeries, said the lawsuits reminded him of other touted medical products that came on the market only later to be found to be harmful to patients -- products like Merck's COX-2 inhibitor, rofecoxib (Vioxx) and .
With Infuse, some of the cases may be attorneys drumming up business, but some represent patients who were harmed, Deyo said.
"My cynical view is that companies view this as the cost of doing business," he said.
The patient lawsuits, which were detailed in a recent securities filing by the company, are the latest development in a decade-long saga of a product that has been at the center of investigations, both scientific and legal, as well as a long list of conflict-riddled research done by physicians who received millions of dollars in royalties from Medtronic, while publishing highly favorable articles about Infuse.
"This is a snowballing effect," said Eugene Carragee, MD, head of spine surgery at Stanford University.
Carragee, editor-in-chief of the Spine Journal, which published its own critical review of BMP-2 in 2011, said the lawsuits represent "a whole lot of people" who got a product that never really showed that it was more beneficial than methods used in traditional spinal fusion surgery.
Over the course of 15 years, Medtronic paid $210 million to a group of 13 doctors and two corporations linked to doctors, including more than $34 million to University of Wisconsin orthopedic surgeon Thomas Zdeblick, who co-authored a series of papers about the product.
In addition to the Spine Journal review, there was a damning 2012 U.S. Senate Committee on Finance investigation of Infuse that was started in part because of Journal Sentinel-MedPage Today stories. The finance committee concluded that Medtronic executives secretly drafted some of those favorable journal articles.
In 2013, two independent reports found that Infuse offered little benefit over conventional spine surgery and raised questions about the possibility that the product was linked to serious adverse events including cancer and sterility in men.
The product also can cause the growth of unwanted bone.
In its securities filing, Medtronic said that at the end of its fiscal third quarter of 2014 about 700 lawsuits involving about 1,000 people had been filed over Infuse in state and federal courts.
It also said that law firms have told the company that a large number of similar claims may be brought in the future.
The company said it had not recorded any expense related to potential damages from the lawsuits.
"Additionally, the company cannot reasonably estimate the range of loss, if any, that may result from these matters," it said.
In addition, the company said it has received subpoenas or document requests from government bodies, including civil investigations from state attorneys general in Massachusetts, California, Oregon, Illinois, and Washington.
"The company is fully cooperating with these requests," the Medtronic said.
Also in the SEC filing the company said it expects continued scientific and clinical research scrutiny focused on the safety and efficacy of Infuse in real-world, clinical experience.
Infuse is a biologic agent that stimulates bone growth and has been implanted in the spines of more than 1 million people, most of whom got it in unapproved ways, or so-called off-label use. As much as 85% of BMP-2 use has been off label.
At its height, the product generated sales of $800 million a year, though sales have declined substantially since 2011.
"When you start using a product 85% off label, there are going to be problems," said Dan Spengler, MD, a Vanderbilt University orthopedic surgeon.
Spengler said he suspected that many of the lawsuits involved patients who experienced excess bone growth that occurred after an off-label surgery.
John Fauber received the Association for Medical Ethics Award for Outstanding Achievement in Journalism and Advancing Transparency in Medicine for his reporting on Infuse and other conflicts of interest in medicine.