The study, which may revolutionize the way physicians diagnose and treat back aliments, will receive the 1999 Volvo Corporation Award for the Clinical Study of Low Back Pain. Carragee, a Stanford associate professor of functional restoration, estimates that up to five percent of the working population in the United States is disabled by low back pain on any given day. Until now, tears in the vertebral discs that cushion the spine have been thought to be the culprit for most of these low back pain complaints. Like spongy coasters sandwiched between each vertebra, the cartilaginous discs protect the bones from banging against each other during running or jumping. According to Carragee, acting as the body's shock absorber takes its toll.
Discs become increasingly susceptible to tears or rupture as they age.
The presence of a tear is confirmed by a discography, in which a physician injects a dye into the suspect disc. Dye leaking out of the disc center into the surrounding area sometimes causes pain. But when the Stanford researchers completed a rigorous comparison of the MRI and discography results of 96 patients with known risk factors for disc degeneration, they found something surprising. People whose discs had high intensity zones were only slightly more likely to experience back pain during normal activity than those without obvious disc problems. A better predictor of pain, they found, is an abnormal result on psychometric testing administered to all the study patients before the examinations.