Trends in diagnostic imaging for low back pain: Has MR imaging been a substitute or add-on?

PURPOSE: To assess whether magnetic resonance (MR) imaging has replaced other diagnostic imaging modalities in the evaluation of persistent low back pain. MATERIALS AND METHODS: Data on diagnostic imaging use in 2,374 adult patients with persistent low back pain in 1987-1990 were analyzed. Multiple logistic regression was used to estimate the annual adjusted odds of lumbosacral spine radiography, MR imaging, unenhanced computed tomography (CT), or CT myelography use. The national cost of diagnostic imaging for persistent low back pain in 1990 relative to 1987 was estimated. RESULTS: The adjusted odds of performing MR imaging in 1990 relative to 1987 was 3.44 (95% confidence interval, 2.63, 4.51), which reflects an estimated increase from 22 studies per 100 enrollees in 1987 to 75 studies per 100 enrollees in 1990. Use of MR imaging in combination with radiography, unenhanced CT, or CT myelography increased. The additional national cost of diagnostic imaging for persistent low back pain in 1990 relative to 1987 was estimated at $70-$176 million. CONCLUSION: MR imaging was used primarily as an add-on rather than a substitute for other imaging modalities in the evaluation of persistent low back pain. Thus, the volume and cost of diagnostic imaging for persistent low back pain have increased.