A U.S. Senate report alleged Thursday that Medtronic was heavily involved in shaping the content of medical journal articles about a bone growth product used in spine surgery, an action the report says is a violation of patients' trust.

Medtronic's role in influencing articles authored by its physician consultants was not disclosed, the report found, raising questions about research conducted by physicians who received $210 million in royalties and consulting fees over 15 years from the Fridley-based company.

According to the report from the Senate Finance Committee staff, the world's biggest maker of heart-rhythm devices helped write, edit and shape at least 11 medical journal articles about its Infuse product.

Medtronic fired back in a statement, saying that it disagreed with many of the findings. In particular, Medtronic "vigorously disagrees with any suggestion that the company improperly influenced or authored any of the peer-reviewed published manuscripts discussed in the report, or that Medtronic intended to underreport adverse events."

Medtronic also called the report's characterization of payments to physicians "misleading and unfair." The company said the vast majority of payments were made to compensate physicians for their intellectual property rights.

Questions about the spinal business have plagued Medtronic for several years, and the company paid $40 million to settle whistleblower lawsuits in 2006 without admitting wrongdoing. Medtronic currently has Yale University researchers reviewing the safety and effectiveness of Infuse.

Dr. Sidney Wolfe, who oversees health care issues at the consumer-oriented advocacy group Public Citizen, called the allegations that Medtronic manipulated scholarly research "dangerous."

"Ask any editor of a respected medical journal if this is typical," Wolfe said, "and they would laugh or get outraged."

Physician authors named in the report as being paid by, and collaborating with, Medtronic included Dr. Ensor Transfeldt of Twin Cities Spine Center, which is among the nation's largest practices. The report found that Transfeldt was paid more than $3.5 million from 1996 through 2010, while Inspire LLC, which is owned by a group of physicians including Transfeldt, was paid $2.9 million from 2007 through 2010.

A call to Transfeldt on Thursday seeking comment was not immediately returned.

The committee's report comes from information contained in more than 5,000 documents subpoenaed from Medtronic. The committee said its inquiry was prompted by reports alleging that "physician authors who had financial ties to Medtronic failed to report dangerous side effects associated with Infuse. These dangerous side effects were subsequently reported by medical researchers that did not have financial relationships with the company."

Sen. Max Baucus, a Montana Democrat who is chairman of the Senate Finance Committee, said: "Medical journal articles should convey an accurate picture of the risks and benefits of drugs and medical devices, but patients are at serious risk when companies distort the facts the way Medtronic has."

Medtronic is paying $2.5 million to the Yale researchers to determine the safety and effectiveness of Infuse. Leading the effort is Dr. Harlan Krumholz, a nationally known physician and advocate of patient safety and transparency in clinical studies. That study is expected to be complete in January.

On Thursday, Krumholz -- who had not yet seen the committee report -- said something has to change to restore integrity and transparency to research.

"Time and time again, I have seen instances where the process is not fully independent and, at the end, the science is being commingled with other interests," he said. He praised Medtronic's decision to commission the Yale study and its decision to make the results of that study open and available to the medical community.

"We have got to get to an era where it's not 'Trust me, this is what I found,' but 'Look at it for yourself,'" he said.

Big-selling beginning

The U.S. Food and Drug Administration (FDA) approved Infuse in 2002 for use in the lower back, and sales soared. At one point, Infuse was bringing in almost $900 million a year.

Allegations later surfaced, though, that Medtronic was coaxing doctors to use it in ways regulators hadn't approved -- such as in neck surgery. In 2008, the FDA issued a warning after reports of excessive bone growth surfaced. While it isn't illegal for doctors to use devices as they see fit, companies cannot market off-label uses of their products.

Several former Medtronic employees, including the spine business' onetime general counsel, filed whistleblower lawsuits alleging that the company courted doctors with rich consulting deals and perks.

In 2006, Medtronic paid the $40 million fine to settle with the Justice Department but admitted no wrongdoing. In May, federal prosecutors closed an investigation of Infuse after finding no wrongdoing.