The multibillion-dollar spine industry faces mounting demands to prove the value of back surgery.

In recent years, spine sales have surged for companies such as Medtronic ( MDT) and Zimmer ( ZMH). The companies have won over surgeons and patients alike with new technologies that promise welcome relief from severe back pain.

But Medicare is now seeking hard, scientific evidence that can support the huge jump in fusion surgeries among seniors and other patients that it covers. Prior to a big meeting in late November, Medicare hinted that past studies -- already lacking in number and scope -- fall short of justifying such operations. Then, just a week before the Medicare panel convened, results from the biggest spine study of its kind rolled in.

On the surface, at least, that study -- popularly known as Sport -- suggested that patients fare equally well whether they undergo back surgery or not. But prominent spine experts, including consultants for Medtronic, showed up to attack the study and caution Medicare officials against jumping to conclusions.

Spine surgeons worried that Medicare might confuse operations for two very different back problems -- on the basis of a study they consider flawed -- and stir up reimbursement nightmares in the process.

Ultimately, Medicare panelists listened to those experts. The agency will now wait on new studies before revisiting its coverage of spinal fusions.

Still, the panel exposed a telling situation in the meantime. The spine industry knows that it must better prove itself if it hopes to keep pursuing lucrative growth opportunities.

"We believe that the Medicare meeting on lumbar spinal fusion represents the opening salvo in a multiyear process," Bernstein Research analyst Bruce Nudell wrote days before the hearing. "We ... regard the Nov. 30 advisory panel meeting as a first step towards defining the studies required to answer the questions" surrounding spinal fusion surgery.

Nudell feels comfortable with his outlook for spine leader Medtronic in the meantime. He has a market-perform rating on the shares, which fell 26 cents to $53.59 on Wednesday. Shares of Johnson & Johnson ( JNJ), another big spine player, slipped 2 cents to $66.24.

Questionable Timing

Spine surgeons entered November's Medicare meeting with a mixture of anger and dread.

To be sure, they had weathered some tough weeks before then. First, in late fall, James Weinstein -- a big-name researcher and outspoken patient advocate -- published a controversial article as the editor-in-chief of Spine. Weinstein wrote about the explosive growth in spinal fusions, noting huge variations by geography, and raised questions about the need for some of those operations in the process.

Other spine experts felt troubled by the timing, as well as the content, of that article.

"This was not new data," insists John Peloza, a Dallas spine surgeon who has provided consulting services for Medtronic in the past. "It was the same data they have been pushing and publishing for years. And the data didn't even support any of Weinstein's conclusions."

Peloza offers his own theories for the rise in spinal fusions. For starters, he says, the population increased significantly during the time period that Weinstein evaluated. Likewise, he says, the number of doctors trained in spine surgery -- a group that now includes neurosurgeons as well as orthopedists -- has exploded as well. But most importantly, he claims, the tools available for spine treatment have advanced considerably.

"The technology has improved at light speed," Peloza says. "It's like improvements in information technology. Everything I used 16 years ago, when I first started practicing, is in a museum by now."

'PR Spin'

Weinstein followed up by publishing the first results from Sport -- a study considered ambitious even by its critics -- a few weeks later.

Weinstein's colleagues had hoped he would share those results with them first, months earlier, at the big annual meeting hosted by the North American Spine Society. But rather than seeking their feedback, they say, he went to the media -- even before his article appeared in the Journal of the American Medical Association -- and broadcast his message there instead.

"What angered surgeons was the PR spin," says Hallett Mathews, a spine surgeon who has been hired by Medtronic. "No matter how you interpreted the data, surgery worked better. ... But you couldn't see that in the headlines."

For his part, Weinstein claims that JAMA restricted him from sharing the Sport results at the NASS meeting because it wished to publicize them itself. He also feels comfortable that the real findings of that study -- supporting surgery and conservative care alike -- did, in fact, get out.

Still, with so much on the line, Weinstein faces backlash from his own colleagues. Some of them have already planned letters to JAMA, demanding more details about Sport, because they feel that the record needs to be set straight.

"It's frustrating," says Brian Subach, a surgeon at the Virginia Spine Institute. "This disinformation campaign has really set me back."

'Primitive' Study

Of course, spine surgeons have encountered plenty of unwelcome news by now.

Indeed, if anything, a recent European study raised more questions about back surgery than Sport itself did. Surgeons attacked that study as well.

"That study just looked at 'back pain,'" Peloza says. "That's like doing a study on chest pain. A lot of things can cause it."

For example, Peloza says, some patients suffer from chest pain as a result of angina. For those patients, he says, nitroglycerin works well. However, he says, for patients with chest pains caused by other problems -- such as asthma, pneumonia or reflux -- nitroglycerin would look like an outright failure.

Similarly, Peloza says, different back problems require different types of treatment. Yet, he says, patients in the European back study often underwent fusion surgery whether it was the ideal treatment for their condition or not.

"It was primitive," Peloza says. "No wonder they had bad results."

New Debate

Spine experts hope for more sophisticated studies going forward.

They see some major progress already. In recent years, they say, device makers have carried out well-designed trials examining some of the most advanced treatments available for severe back pain. Those trials compared two operations, fusion and disc replacement, and showed positive outcomes for both.

In comparison, Sport -- with its heavy focus on conservative care -- looks outdated to some.

But Subach fears additional fallout nonetheless. Weinstein, he notes, has so far published only the first of three back studies included in Sport.

"I'm just waiting for the other shoe to drop," Subach says.

But Nudell sounds less concerned. Notably, he doubts that health insurers will stop covering fusion surgeries regardless of what Sport shows. Down the road, in fact, he questions whether Sport will matter much at all.

"We'll see more and more quasi-fusions and motion-sparing devices," he says. "So the debate will change.

"That," he concludes, "is the beauty of industry."