A top spine surgeon at the University of Minnesota who has reaped more than $1 million consulting for Medtronic Inc. is facing tough questions from a prominent U.S. senator investigating financial conflicts in medicine.

In a July 24 letter, Sen. Charles Grassley, R-Iowa, also asks the university pointed questions about how it monitors potential conflicts of interest involving medical school doctors who receive consulting payments from medical device companies.

But the real fire in the 142-page letter is aimed at Dr. David Polly, 52, a nationally known surgeon who heads the spine service at the U's Department of Orthopaedic Surgery.

Grassley asserts that Polly testified before a Senate committee without disclosing that he was being paid by Medtronic; alerted Medtronic to the progress of government-sponsored research in violation of an agreement with the university; and may have given inaccurate information to a university ethics committee.

According to documents culled during Grassley's nearly two-year investigation, Polly received $1.2 million in consulting fees, honoraria and expenses from Fridley-based Medtronic between 2003 and 2007.

In an interview following three spine surgeries Tuesday, Polly said he never hid his relationship with Medtronic and followed all the university's disclosure rules. He defended the role physicians play in working with medical device companies as crucial to improving the quality of medical devices and, by extension, patient care.

"You can develop drugs without clinician input, but when you're building things that go into people and are used by surgeons, what an engineer thinks will work and what will actually work are not necessarily the same thing. We report back on what works and what doesn't," he said.

Medtronic said in a statement late Tuesday that "based on information that has come up in several outside inquiries, Medtronic has decided to investigate Dr. Polly's consulting relationship and activities to our company." The company did not offer specifics on the impending probe.

While the university requires physicians to report financial compensation from these business relationships, there is no limit on the amount they can receive. Further, even though Polly received more than $200,000 a year from Medtronic between 2004 and 2007, he was required by the U only to check a box stating he received "in excess of $10,000."

The U's Medical School has approved a new conflict of interest policy that requires more detailed and public disclosure of these relationships, but that document is on hold for the time being.

In the past year, Grassley has trained an investigative eye on medical device companies and the relationships they forge with influential doctors, particularly in the fast-growing spine surgery field, and those who work at research institutions such as the U. He has co-sponsored federal legislation to make these relationships public.

In the letter to University President Robert Bruininks, Grassley stated, "actions taken by thought leaders, like those at the University of Minnesota, often have a profound impact upon the decisions made by taxpayer-funded programs like Medicare and Medicaid, and the way that patients are treated."

Polly's compensation from Medtronic -- the world's largest medical technology company with $14.6 billion in annual revenue -- caught the interest of the University's Conflict Review and Management Committee in late 2006.

The committee ultimately determined that a conflict existed because Polly was the primary investigator in a study using a Medtronic bone-growth product in rats that was sponsored by a $446,000 Department of Defense grant -- but at the same time was a paid company consultant.

The 2007 study, which is just one of 96 peer-reviewed studies bearing Polly's name, appears to have captured Grassley's interest for a number of reasons. He claims Polly may have given inaccurate information to the review committee about the often-controversial Medtronic spine-mending product, which is called Infuse.

Polly allegedly said it was the only commercially available product of its kind, when another product made by Stryker was also available. Polly responded Tuesday that the Stryker product was not "routinely commercially available'' and had restrictions placed on its use by the Food and Drug Administration.

Ultimately, the committee found that Polly's conflict was "manageable," but stipulated that he could not inform Medtronic of any study finding until it was publicly available. However, Grassley claims that the following month, Polly billed Medtronic $594 for work on an "infection study write-up." Polly said Tuesday the billing was for a different study.

Grassley said he was also "alarmed to learn" that Polly billed Medtronic to testify before Congress but never informed the Senate, saying only that he represented the American Academy of Orthopaedic Surgeons. For the two days Polly was in Washington, D.C., to testify in support of the Defense Department grant, Polly billed the company $7,000, according to Grassley.

All told, Grassley determined that Polly billed Medtronic more than $50,000 for several months of "lobbying" on behalf of the grant.

Medtronic spokeswoman Marybeth Thorsgaard said in a statement, "While we reimbursed Dr. Polly for his prep time and travel in connection with the hearing, to the best of our knowledge, we were not aware that he did not disclose his relationship with the company and expected that he would have done so."

Polly said the grant supported research for patients who have open leg fractures -- such as those who were in motorcycle accidents or suffering from war injuries -- and have few other options medically. (Polly is the former head of orthopedic surgery at Walter Reed Army Medical Center.)

The bone-growth product used in the study and hundreds of others has proven to be a blockbuster product for Medtronic, although it has been occasionally controversial when used in ways not approved by federal regulators. Medtronic faces a Department of Justice investigation on how the product is used in "off-label" ways.

It's unclear whether the U's conflict committee followed up on whether Polly complied with its "conflict management plan" crafted in 2006. General counsel Mark Rotenberg said typically the appropriate department dean and the faculty member themselves would monitor the compliance effort.

Wrote Grassley: "There is no way to validate or verify the accuracy of the information that faculty members report in their disclosure statements. Therefore, it is unclear to me how University conflict of interest officials are able to make proper assessments of research conflicts without considering the level of financial interest as a mitigating factor when making determinations."

Rotenberg said the U will have a response ready for Grassley by the required Aug. 7 deadline.

Asked why Grassley's sweeping investigation has targeted him, Polly said simply, "I don't know. ... Senator Grassley has an agenda and a job to do, and in his mind, he's doing his job, and in his mind, he's watching out for things perpetuated on the American public that are not appropriate or optimal.

"What I don't want to see happen is we throw the baby out with the bathwater -- some good things have come out of [bone growth products like Infuse]. It works pretty darn well. ... That's not to say there aren't problems; there are. Any time you use things in a way that is not well studied, you have to be careful.''

Janet Moore • 612-673-7752