The family of a California woman who died after neck surgery has filed a lawsuit against Fridley-based Medtronic Inc., claiming the company's controversial bone-growth product caused her death.

The suit appears to be the first public allegation that a patient died because Medtronic's Infuse product was used in ways not approved by regulators. The complaint, filed late Tuesday in U.S. District Court in Los Angeles, claims that hundreds of other patients also have been harmed.

A blockbuster product for Medtronic since 2002, with sales reportedly exceeding $800 million annually, Infuse lately has triggered a series of investigations and lawsuits.

"Off-label" use of the product -- that is, in ways not approved by the Food and Drug Administration (FDA) -- is the target of recently begun investigations by the Justice Department and by Sens. Charles Grassley, R-Iowa., and Herb Kohl, D-Wis. The FDA issued a warning to doctors in July about use of the product for procedures in the neck, because it's only approved to treat the lower back and for dental applications.

In addition, a whistleblower lawsuit filed by two former Medtronic employees against some of the nation's top spine surgeons alleges that the company paid the physicians thousands of dollars in consulting fees to encourage off-label use of the product. It is not illegal for doctors to use a medical device off-label, but companies such as Medtronic cannot promote the practice.

The California woman, Shirley Nisbet, 74, was among those treated with Infuse in the neck. She developed complications following surgery in August, lapsed into a coma and died nine days later, according to the California lawsuit.

Infuse promotes bone growth. The FDA said in its recent warning that it could cause swelling of the neck and throat, as well as difficulty in swallowing, breathing and speaking severe enough to require emergency care.

That appears to have happened to Nisbet, according to the family's suit. Five days after surgery, "her breathing became so compromised because of neck swelling and compression to her airway that she stopped breathing altogether and went into full respiratory arrest,'' the suit says. Because it took several minutes to insert a breathing tube, her brain was deprived of oxygen and "she remained in a vegetative state," until her death, the suit says.

The suit further alleges that a Medtronic sales representative, present during the surgery, recommended use of Infuse to Nisbet's surgeon.

Medtronic said Wednesday its sales representative denies recommending off-label use of Infuse for Nisbet. The company quoted Nisbet's surgeon saying his use of Infuse was "based on my personal experience with the product and evidence presented at our professional medical society meetings, and had nothing to do with the Medtronic technical expert."

Medtronic said that the presence of a technical representative brings "special product expertise [that] enhances patient safety."

As of mid-November, no deaths have been attributed to off-label use of Infuse, according to an FDA spokesman.

Janet Moore • 612-673-7752