WASHINGTON (Reuters) – Bone growth products made by Medtronic Inc and Stryker Corp have been linked to life-threatening complications when used without approval in neck fusion surgeries, the U.S. Food and Drug Administration warned on Tuesday.

The FDA said it has received at least 38 reports in the last four years of neck swelling and breathing problems in patients given the products, which are not FDA-cleared for use in the neck.

Medtronic and Stryker make types of recombinant human bone morphogenetic proteins used to help treat degenerative disc disease, fractures and other bone conditions. InFuse Bone Graft by Medtronic and OP-1 Implant and OP-1 Putty by Stryker both contain such protein.

Representatives for the companies either could not be immediately reached or had no immediate comment.

Daniel Schultz, head of the FDA’s device center, said it was not clear what caused the complications or whether certain patients were at greater risk. He said the neck’s close proximity to critical airways was part of the problem.

In some cases, patients had to have a tube inserted to help them breathe or had to have a tracheotomy. Others were given medications or underwent further surgery.

Most of the complications arose between two days and two weeks after surgery, Schultz said in a letter to doctors posted on the agency’s website.

The letter is online at http://www.fda.gov/cdrh/safety/070108-rhbmp.html.

(Editing by Braden Reddall)