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Obesity a key Factor in Treatment of Lower Back Disorders

Research trial indicates nonoperative treatment is not effective in obese patients.

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By: Michael Barbella

Managing Editor

Bigger isn’t always better, particularly when it comes to treating lower back pain.

Results of a Spine Patient Outcomes Research Trial (SPORT) indicate that obesity influences the results of lumbar degenerative disorder treatments.

“Obesity does have an affect on the outcomes of nonoperative and operative treatment of degenerative conditions of the lumbar spine,” said Jeffrey Rihn, M.D., assistant professor in the Department of Orthopedic Surgery at Thomas Jefferson University Hospital in Philadelphia, Pa. “It is important to understand these effects when counseling patients prior to surgery and when determining an appropriate treatment plan.”

Rihn presented findings of the SPORT earlier this month at the North American Spine Society’s 25th Annual Meeting in Orlando, Fla.

Using combined randomized and observational cohorts from the SPORT study, Rihn and several colleagues studied ways in which obesity affects outcomes for lumbar intervertebral disc herniation, spinal stenosis and degenerative spondylolisthesis.

Researchers compared obese patients (those with a body mass index [BMI] greater than or equal to 30) with non-obese patients (those with a BMI less than 30). To measure outcomes, the researchers used the Oswestry Disability Index (ODI), the SF-36 bodily pain (BP) and physical function (PF) scores.

Whether treated operatively or nonoperatively, patients improved from baseline in every primary outcome measure at four years’ follow-up, according to the researchers. For both BMI groups in the lumbar disc herniation and stenosis cohorts, surgical complication and reoperation rates were the same. Degenerative spondylolisthesis patients who were obese experienced a higher postoperative infection rate (5 percent vs. 1 percent, P=0.05) and twice the reoperation rate (20 percent vs. 11 percent, P=0.01) than nonobese patients. Surgery was equally effective in both BMI groups for stenosis and degenerative spondylolisthesis.

There was only one exception: obese patients with degenerative spondylolisthesis had worse SF-36 PF scores compared to non-obese patients (27.1 vs. 22.6, P=0.017). Obese patients with lumbar disc herniation did not do as well as non-obese patients, Rihn said.

Nonoperative treatment may not be the best option for patients who are obese, the results showed. Obese patients with stenosis did worse in all three primary outcome measures. And obese patients with lumbar disc herniation and degenerative spondylolisthesis had similar SF-36 scores but worse ODI results.

“We were surprised that nonoperative treatment did not seem to be as effective in obese patients for all three degenerative lumbar conditions that were studied,” Rihn said at the meeting.

For spinal stenosis and degenerative spondylolisthesis, the treatment effect was significantly different between obese and nonobese patients, “suggesting that surgery is more effective than nonoperative treatment in patients who are obese,” Rihn said. “That was surprising.”

Overall, obesity influenced treatment outcomes in all three groups in different ways, according to Rihn.

“This is likely due to the fact that these conditions, particularly when comparing disc herniation to either stenosis or degenerative spondylolisthesis, vary in patient demographics and pathophysiology,” he noted. “In the SPORT study, patients with disc herniation were younger [average age early 40s] and more likely to work either full- or part-time. Patients with stenosis, however, were older [average age mid- to late-60s] and were less likely to be employed.”

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