RSNA: Sitting Up Straight Called Stressful on the Spine

CHICAGO, Nov. 27 -- Neither slouching in a chair nor sitting up straight is good for the back, according to researchers from Scotland.

A healthier posture for sitting is a semi-reclined position in which the hips are slightly higher than the knees, said Waseem Amir Bashir, M.B., Ch.B., and Francis Smith, M.D., of the University of Aberdeen, who conducted a pilot study that used MRI to assess the effects of different sitting postures on spinal disks.

Twenty-two healthy volunteers, 10 men and 12 women, mean age 34, underwent MRI imaging of the spine while in a supine position, said Dr. Smith at the Radiological Society of North America meeting here. This served as the control because there was no pull of gravity on the intervertebral disk and the nucleus pulposus remained perfectly centered.

MRI scans of the spine were then obtained as the volunteers sat upright in a 90% position, again when they were slouched forward as if hunched over a computer keyboard, and finally when they were slightly reclined with hips above the knees "much the way a Formula One race car driver sits in the cockpit of the car," said Dr. Bashir.

In the latter position the angle between the trunk and thighs is approximately 135%.

And that position really is a formula for a healthy spine, because it placed the least stress on the lumbar spine as evidenced by less decrease in intervertebral disc height and the nucleus pulposus remained well-centered, Dr. Smith said.

By contrast, MRI images performed when the volunteers sat upright showed the "nucleus pulled posterior as did the images of people in a slouching position," Dr. Bashir said. Moreover, both positions decreased intervertebral disk height.

Dr. Smith said that this MRI study confirmed a hypothesis first put forth in 1953 that there was a relationship between lordosis and trunk-thigh angle."

In order to conduct the study they used a 0.6 Tesla whole-body positional MRI scanner, which allowed the patients to be scanned in a number of positions in addition to the traditional prone or supine position, Dr. Smith said.

Dr. Smith said this study would serve as a control for the next stage of the research-using MRI to evaluate the efficacy of treatments for low back pain. "Our plan is to work with orthopedic surgeons to evaluate various treatment options," he said.

Meanwhile, Dr. Smith recommended that primary care physicians advise patients with chronic back pain to "avoid both slouching and sitting upright," although he said it is unclear if following his advice for good posture will reduce pain.

Dr. Smith added that one way to reduce spine stress while seated would be to "sit on an exercise ball instead of a standard desk chair." The ball, he said, forces "you to sit in a way that your hips are higher than your thighs."

Joseph Tashjian, M.D., president of St. Paul Radiology and moderator of the RSNA press briefing where the results were presented, said he thought the real benefit of the findings will be to "aid in design of the work place."

The study confirmed "what many of proponents of ergonomic design have already suggested," he said.