A union fund that invested in Medtronic Inc. – the country’s largest manufacturer of medical devices – can move forward with its Medtronic class action lawsuit against the company for allegedly manipulating studies about the safety of the Infuse bone graft system, a federal judge has ruled. The manipulated studies allegedly misled investors about the company’s financial situation and drove up stock prices.

The Medtronic class action lawsuit accuses the medical device maker of conspiring with researchers to both hide Infuse bone graft risks, and after the risks became known, of not disclosing that surgeons discontinued using the product, resulting in an inflated and then deflated stock price. The Medtronic class action lawsuit was filed by the West Virginia Pipe Trades Health & Welfare Fund.

Medtronic is also the subject of thousands of lawsuits over Infuse, a bone graft growth product which uses a genetically modified version of a naturally-occurring protein that encourages expedited bone growth. The Infuse lawsuits accused the manufacturer of intentionally minimizing the bone graft product’s problems.

The U.S. Food and Drug Administration (FDA) approved Infuse in 2002 for specific uses, such as lower back fusion surgery. But many patients, as many as 50 percent in some cases, experienced a plethora of complications, including male sterility and other uro-genital injuries, nerve damage, excessive bone growth, chronic pain, and difficulty breathing, swallowing, and speaking. Patients also accused Medtronic of marketing the Infuse bone graft for off-label uses, putting thousands of spine surgery patients at risk for dangerous complications.

In 2011, The Spine Journal reported that Infuse’s adverse effects “were not properly reported in clinical research.” The medical journal highlighted the conflicts of interests of many researchers who studied the product while being paid between $12 million and $15 million to do so, totaling about $200 million.

Before The Spine Journal piece was published in June 2011, the Infuse bone graft represented 21 percent of Medtronic’s revenue, or approximately $900 million, according to the Infuse lawsuit.

Arthritis and other forms of back pain lead people to back surgery, predominantly bone grafts, which are intended to mitigate back pain via spinal fusion. During this procedure, damaged bones in the spine are fused together to form one solid bone, instead of individual vertebrae, purportedly to end pain caused by nerves rubbing along the spine. More than 400,000 spinal fusions are performed each year in the United States.

Studies have shown that Infuse can inflame tissue and bone near the surgery site and may even stimulate cancer growth. The synthetic bone morphogenetic protein used causes side effects such as inflammation, back and leg pain, radiculitis (pain that spreads through the spinal nerves), implant displacement, retrograde ejaculation (occurs when semen enters the bladder), male sterility, cancer, infection, osteolysis (degeneration of bone tissue), ectopic bone formation (unwanted bone in the spinal canal) and in some cases, death.

Two whistleblower lawsuits were filed after revelations that Medtronic was promoting non-approved, off-label uses for the drug. In 2006, the Justice Department settled with Medtronic for $40 million.

In 2012, Reuters reported that Medtronic confirmed that it agreed to pay $85 million to settle a lawsuit brought by shareholders accusing the company of failing to disclose that as much as 85 percent of Infuse sales depended on so-called “off-label” uses. Medtronic’s share price and Infuse sales fell dramatically after the company disclosed that the Justice Department and the U.S. Senate were investigating the product’s off-market use.