Although chiropractors' office rates are lower than physicians', they end up charging more because they require many more visits.
On the other hand, the study found patients are somewhat more satisfied with chiropractors' care, largely because these practitioners do a better job of explaining what is wrong with their backs.
The study, conducted by medical doctors at the University of North Carolina, is unlikely to settle the touchy issue of whether chiropractors do a better job than physicians on bad backs. It contradicts several earlier reports showing that spinal manipulation by chiropractors seems to hasten healing.
"Regardless of whom they see, people appear to get better at the same rate,'' said Dr. Timothy S. Carey, the lead author.
His study, financed by the U.S. Agency for Health Care Policy and Research, was published in Thursday's issue of the New England Journal of Medicine.
The doctors surveyed back pain patients who went to see primary care doctors in private practice and at HMOs, as well as orthopedic surgeons and chiropractors in both cities and rural areas, all in North Carolina.
Six months after they hurt their backs, 95% of the patients were able to do everything they could before their injuries. There was no difference in how fast they got better.
Among physicians, the orthopedic surgeons were most expensive, because they were often ordered up expensive diagnostic scans.
City-based primary care doctors were the cheapest, charging a median of $169 for each patient, while their rural counterparts charged $214. The cost at HMOs was $184, while orthopedists charged $383.
Rural chiropractors charged $348 per patient, while those in cities charged $545.
Doctors typically took care of patients in four or five visits, while chiropractors required 10 or 15.
Chiropractor Jerome F. McAndrews of Tulsa, Okla., a spokesman for the American Chiropractic Association, said he was not surprised to see that patients were happiest with chiropractic care.
"We naturally have more visits, because our goal is different,'' he said. "We are attempting to restore balance to the system rather than just treat the point of pain.''
Chiropractors treat back pain principally with spinal manipulation, while physicians typically offer painkillers, anti-inflammatory medicines, advice and reassurance.
Experts generally recommend that people with low back pain avoid bed rest, stay active, get some mild exercise and take over-the-counter pain relievers.
Guidelines from the Agency for Health Care Policy and Research say nine out of 10 patients will recover on their own within a month. However, the study did not examine the alternative of not seeing a doctor at all.
"Because back pain is so disabling, it is difficult to completely eliminate care-seeking,'' Carey said. "They want to see a doctor. They want pain relief and reassurance that nothing serious is going on.''
By The Associated Press