People who get steroid injections to ease back pain often get an imaging scan first. But the $1,500 scan does little good for the patient, and adds significantly to the cost of care, according to a new study published in the Archives of Internal Medicine.

Back-pain injections, a common treatment at pain clinics, are frequently preceded by a magnetic resonance imaging (MRI) scan. But doctors have come under fire recently for ordering too many unnecessary imaging tests.

“Our results suggest that MRI is unlikely to avert a procedure, diminish complications or improve outcomes,” said study author Dr. Steven Cohen of Johns Hopkins University School of Medicine

In the study, 132 patients with sciatica – in which a pinched nerve in the lower back causes shooting pain down the leg – were treated with cortisone shots along the spine to ease inflammation and pain. All received an MRI beforehand. Doctors used the MRI results to guide their treatment of half the patients; for the other half, doctors did not see the MRI results before treatment.

Researchers found no significant difference among the patients three months after the treatment.

Lower back pain is one the top reasons people see medical attention in the U.S., and treating back problems costs over $85 billion a year in the U.S., according to a separate study published in the Journal of the American Medical Association.