Study: Medtronic Product Increases Sterility in Men

A study that appeared in the June issue of The Spine Journal found that back surgery patients treated with Medtronic's Infuse product experienced higher rates of sterility; Medtronic and two surgeons involved in the original Infuse trial contend that not enough men experienced such complications to statistically link the problem to the Infuse product.

A study released Wednesday suggests that a best-selling bone-growth product made by Fridley-based Medtronic, Inc., may increase the risk of sterility in men.

The study, published in the June issue of The Spine Journal, was conducted by a surgeon at Stanford University. It analyzed 243 patients who had back surgery and found that those treated with Medtronic's Infuse product experienced higher rates of sterility.

Sixty-nine patients in the study group were treated with Medtronic's Infuse product, and 174 received a bone graft-another material that can be used to fuse spinal vertebrae. Among the patients treated with Infuse, five men (or 7.2 percent) developed a complication called retrograde ejaculation (RE), where semen is misdirected into the bladder; by contrast, only one patient who received a bone graft (representing 0.6 percent of that group) experienced RE. According to the study, the condition eventually resolved itself in half of those six patients.

“In my opinion, it is important that men who are considering having children have the opportunity to weigh the risks of the various available procedures so that they can make their best-informed decision,” Dr. Eugene J. Carragee, who conducted the study and edits The Spine Journal, said in a statement.

Infuse is a bioengineered bone growth protein that has been used in spinal fusion procedures for the past nine years. The type of spinal fusion that the study refers to is anterior lumbar fusion, which is performed on about 80,000 patients each year in the United States, according to The New York Times. Infuse is reportedly used in about half of those procedures, and men comprise about half of the patients who get spinal fusions. Women have not experienced Infuse-related sterility complications.

Two surgeons who were involved in the original Infuse trial defended their findings in statements to The New York Times. They contended that not enough men had experienced sterility-related complications in their study to statistically link the problem to the Infuse product. One of the surgeons, Dr. Thomas A. Zdeblick, also said that Carragee's study had limited usefulness because it represented a retrospective look at patients and not an actual clinical trial.

In a statement e-mailed to Twin Cities Business on Thursday morning, Medtronic echoed the surgeons involved in the original Infuse trial: “With an issue like retrograde ejaculation (RE), in which there is literature showing it to be a procedural adverse event, it is important to look at data from randomized, FDA-regulated trials in which there are multiple surgeons participating, instead of looking at data from a non-randomized data set, such as a single surgeon's own patients, as was the case at the Stanford study. In the original randomized clinical trial that was used for supporting FDA approval of Infuse, the number of men who experienced RE was not enough to statistically link the problem to the product.”

Medtronic also said that it disclosed the RE rates following the clinical trial and also included the information in the labeling of the Infuse product.

The company cited a later randomized clinical trial in which 177 patients were treated with Infuse and 405 were treated with a lumbar disc as part of a similar surgical approach. In that study, Medtronic said, the rates of RE were nearly identical among both groups.

Medtronic is the world's largest medical device company and Minnesota's seventh-largest public company based on revenue, which totaled $15.93 billion for the fiscal year that ended April 29. Citing analysts, The New York Times reported that sales of Infuse hit about $900 million during that period.

Medtronic's stock closed down 1.6 percent at $40.23 on Wednesday.