For people with lower back pain, a set of five criteria seem to predict whether spinal manipulation is likely to help them, according to a new study.

Previous research has found mixed results for spinal manipulation, a somewhat controversial technique that many people fear may be dangerous, study author Dr. John D. Childs told AMN Health.

His group found that spinal manipulation tends to work best for people with at least four out of the five following characteristics: low back pain that has lasted less than 16 days, no pain below the knee, a willingness to return to normal activities, stiffness in the lower spine, and relatively good rotation in the hips.

“Not only is manipulation effective, it’s highly effective for a particular subgroup,” Childs said.

During the procedure, meant to increase mobility and reduce pain, a physical therapist, chiropractor, or doctor typically rotates a person with lower back pain and applies a thrust with the hand, “cracking” the back.

In reality, the amount of force professionals apply to the spine during manipulation is actually quite “low,” Childs said.

Childs, who is based at the Lackland Air Force Base in San Antonio, Texas, explained that many theories exist for why manipulation helps, but no one is really sure. “We don’t really understand why it works,” he said in an interview.

To investigate which patients might benefit most from manipulation, Childs and his team tested a recently developed prediction rule for spinal manipulation in a group of 131 patients with lower back pain, between the ages of 18 and 60.

The researchers evaluated whether participants met the rule’s criteria (that is, the previously mentioned characteristics), then asked everyone to do back exercises. Some participants also received two sessions of spinal manipulation.

Among those who received manipulation, individuals who met four out of the five conditions were 13 times more likely to benefit from the treatment as people who didn’t meet the criteria, the researchers report in the Annals of Internal Medicine.

Overall, Childs and his team calculated that people who met the criteria had a 92 percent chance of improving with spinal manipulation.

The study was funded in part by the Foundation for Physical Therapy, Inc.

In an accompanying editorial, Dr. Richard A. Deyo of the University of Washington in Seattle writes that although the report appears to offer a “slam-dunk” in favor of manipulation for certain patients, Childs and his team compared the technique to exercise, which research has not clearly shown to be effective for all types of low back pain.

As a result, the study may have judged manipulation against a “placebo therapy, rather than an effective alternative,” he writes.

Moreover, Deyo notes that the study was performed in military clinics, and the results may not apply to most people treated in primary care clinics.

SOURCE: Annals of Internal Medicine, December 21, 2004.