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Antibiotics were touted in headlines this week as a groundbreaking treatment for chronic lower back pain. The Guardian quoted a prominent British spinal surgeon as saying the experimental treatment, based on Danish research, is worthy of a Nobel Prize.

But Canadian specialists in spinal-cord injury caution that the promise of an antibiotic cure is based on a preliminary pilot study that is far from conclusive.

According to the study, published in April in the European Spine Journal, as many as four in 10 cases of chronic lower back pain may be caused by a bacterial infection that can be cleared up with antibiotics.

Researchers from the Spine Centre of Southern Denmark recruited 162 patients who had suffered lower back pain for at least six months following a herniated disc. The patients also had a type of swelling within the vertebrae known as Modic Type 1 changes.

Patients received either 100 days of antibiotic treatment or a placebo. Compared with patients given a placebo, the treatment group improved significantly in measures of pain and use of sick leave. The improvements persisted in a one-year follow-up.

In an earlier report, also published in the European Spine Journal, the Danish team linked Modic Type 1 changes to bacterial infection. They analyzed tissue from patients who had suffered a slipped disc and found that many tested positive for Propionibacterium acnes – bacteria associated with acne. The researchers suggested that increased blood flow following a herniated disc drew the bacteria to the injury site, causing inflammation and damage to the adjacent vertebrae.

The researchers theorized that antibiotics may be an effective treatment for a common cause of chronic lower back.

But statements that antibiotics will cure chronic lower back pain, which affects an estimated 1 in 5 Canadians, "are not supported by the data presented in the [most recent] study," said Paul Bishop, a spine doctor and researcher at ICORD, a spinal cord injury research centre in Vancouver.

The study design has shortcomings, he said. Although the researchers restricted the study to patients with disc degeneration, they did not exclude patients with other potential pain generators, including arthritis, Bishop explained. "The authors in this study have not used the current standard of diagnostic investigations for establishing that they do, in fact, have a bunch of patients whose pain is coming exclusively from a disc."

Although patients showed improvements after antibiotics treatment, the pain relief may have been due to other effects of the antibiotics, including anti-inflammatory properties, he said.

Preliminary research can be misleading, Bishop pointed out. Not long ago, researchers believed that a molecule known as TNF-alpha was a cause of sciatica, and that sciatica could be cured without surgery with a TNF-alpha inhibitor. "That all turned out to be a sham," Bishop said.

Although the Danish research is promising, the study does not establish that bacteria was the cause of lower pain and that antibiotics were the cure, Bishop said. "That doesn't mean that it isn't a great study," he added. "It just means that it's not a slam-dunk deal that this is the answer."

Mark Frobb, a physician at the Chronic Back Pain Clinic in Surrey, B.C., noted that there are dozens of causes of chronic lower back pain, "and no one treatment will address them all."

The Danish findings must be reproduced in a series of studies before antibiotics are proved to be an effective treatment for a subset of patients with lower back pain, he said. "I think this is probably just a lightning rod for physicians to be more aware that [bacterial infection] may be a cause of chronic low back pain," Frobb said.

He added that it's too soon to say whether antibiotics work better than existing treatments for pain due to a herniated disc, which include thermal treatments and injections of corticosteroids. "Until they're put head to head in controlled trials," he said, "I think that it would be inappropriate to say that we've discovered the panacea for lower back pain."