Oct. 14 (Bloomberg) -- Patients with low back pain may undergo more unnecessary surgery if they have greater access to magnetic resonance imaging machines, a study of Medicare recipients found.

Those in regions with the highest concentration of MRI scanners were about 20 percent more likely to have back surgery than those who lived in an area with the lowest concentration, research online today in the journal Health Affairs showed. Back surgery isn’t proven or recommended to help patients with nonspecific low back pain, the study authors said.

The number of MRI machines tripled in the U.S. to 26.6 machines per 1 million people in 2005 from 7.6 machines per million people in 2000, according to the article. Medicare, the U.S. government health program for the elderly, pays about $600 for a lower back scan, the researchers said. An increase in the number of scans and surgeries is raising the cost of treating lower back pain, according to the study authors.

“Patients for a long time in this country had engrained in them that getting more stuff is better for you,” said study author Laurence Baker, a professor of health research and policy at Stanford University near Palo Alto, California, in a telephone interview yesterday. “More scanning did not make it better, it might make you worse and get you surgery that doesn’t really work. The system as a whole needs to come to terms with how we use things like MRIs and their benefits without bankrupting the system.”

Detailed Images

Makers of MRI scanners include General Electric Co. of Fairfield, Connecticut, Siemens AG of Munich and Amsterdam-based Royal Philips Electronics NV. MRIs use a magnetic field, radio frequency pulses and a computer to produce detailed images of the body.

The machines may pick up abnormalities that are unrelated to the back pain, which can lead to doctors performing surgery that may not benefit the patient, the authors said.

The researchers looked at data from a 20 percent sample of Medicare recipients who received care for low back pain from 1998 to 2005 in 318 metropolitan areas. They linked the patient data with the number of MRI machines in each area. Those in the highest availability areas had at least two times as many MRI machines per capita as those in the lowest availability areas, the authors said.

The study included 666,455 episodes of low back pain. Almost 16 percent of the episodes led to an MRI and 2.7 percent resulted in low back surgery within a year of first visiting the doctor.

Additional MRIs

The researchers found a “clear relationship” between the availability of MRIs and the use of the tests in low back pain patients. Each additional MRI machine added from 1999 to 2004 was associated with eight more low-back scans, the study showed. Expanding those numbers to the entire Medicare population implied about 40 additional procedures for each extra scanner.

The authors projected that in 2004, 5.4 percent fewer low back MRIs and 9 percent fewer back surgeries would’ve been done if all Medicare patients with low-back pain had lived in the areas of lowest MRI availability.

Researchers estimated that 1,825 fewer back surgeries would’ve taken place in 2004 if all patients living in the highest MRI area had lived in the area with the lowest concentration.

“We hope that this study will contribute to the debate over how to restrain the growth of health care spending without reducing access to high-quality care,” Baker wrote in the article with co-author Jacqueline Baras, a Stanford University medical student.

Low back pain is more common than severe headaches, neck pain and facial pain, according to a National Institutes of Health survey. Back pain can limit activity and lead to poor health and psychological distress, according to the American Pain Foundation Web site.

The study was funded by the California Healthcare Foundation and the Stanford Medical Scholars Research Program.

To contact the reporter on this story: Nicole Ostrow in New York at nostrow1@bloomberg.net.

Last Updated: October 14, 2009 15:01 EDT