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Psychological factors may be root of back pain, say Stanford researchers

When it comes to back pain, psychological distress is a more reliable predictor of the problem than imaging and diagnostic disc injection, Stanford University School of Medicine researchers say. Their finding could affect how doctors treat back pain, which often includes costly surgery that insurance companies are increasingly reluctant to cover.

Most adults in the United States will experience disabling lower back pain at least once in their lives, but their doctors frequently can’t find a specific physical cause. In a four-year investigation that followed patients who initially had no lower back pain, researchers studied their subjects’ spines using both disc injection and magnetic resonance imaging, or MRI. And they also got to know their research subjects through psychological evaluations. It turned out that psychological factors more accurately predicted who would develop lower back pain than the two diagnostic techniques.

In people both with and without back pain, MRI can detect cracks or tears in the spongy cartilage disc that cushions each unit of the spine. Some doctors also have suggested that if a patient feels pain when fluid is injected into one of the spine’s discs in a procedure called discography, the patient will soon develop back pain even if he or she doesn’t already feel discomfort.

"It was thought that discography could separate the wheat from the chaff," said Eugene Carragee, MD, professor of orthopedic surgery and lead author of the study, which is published in the May 15 issue of Spine. "But the bottom line is that it didn’t predict who would go on to develop back pain." Carragee and colleagues also found that the invasive discography procedure itself does not injure the spinal disc enough to cause back pain.

Carragee and his team examined 46 discography subjects and 49 control individuals annually over the four-year study period. Some of them had undergone cervical surgery or had been diagnosed with chronic pain syndrome, but none had lower back pain at the start of the study. "Nobody had ever followed a high-risk, asymptomatic group with discography or MRI for such a long period," said Carragee, who also directs Stanford’s Orthopedic Spine Center.

The researchers found that patients with poor coping skills - as measured by psychological testing - or with chronic pain were nearly three times more likely to develop back pain compared to those with neither. A history of disputed workers’ compensation claims also predicted future back pain. Meanwhile, a crack in the disc or a "high-intensity zone" seen on MRI was weakly associated with back pain, but the result was not statistically significant. "The structural problems were really overwhelmed by the psychosocial factors," Carragee said.

Some insurance companies and state workers’ compensation funds are already balking at paying for surgery to treat nonspecific back pain associated with psychosocial problems, he noted. Only a quarter of the 300,000 spinal fusion operations that occur each year are done for obvious reasons, such as tumors, infections or deformities, and just a fraction of the rest - those with pain and ordinary age-related degeneration - have good results from the surgery.

"The question is, can we better identify groups that have a greater chance of being helped by surgery?" Carragee asked. It may be more appropriate to treat other patients by helping them cope with the pain and strengthening their backs, he suggested.

He and his Stanford co-authors, who include Babak Barcohane, MD, Todd Alamin, MD, and Erica van den Haak, are working on a companion five-year study to examine a higher-risk group: patients who already have common lower back pain.

Michelle Brandt | EurekAlert!
Further information:
http://med-www.stanford.edu/MedCenter/MedSchool/