Background: Low back pain has recently been reported as the leading cause for disability worldwide. The diagnostic value of imaging has been estimated low. Led by own positive experience, however, we hypothesized that MRI can detect signs of facet joint pain.
Methods: 15 patients and 15 controls were retrospectively assessed by two readers. They compared de-identified T2 weighted lumbar spine MRI scans. Facet joint size, shape, angle, joint space signal and degeneration were rated. Pain aetiology was proven with the diagnostic gold standard of medial branch blocks.
Results: Facet joint angles and joint diameters were significantly larger in symptomatic patients, who also showed significantly higher grades of degeneration but no difference in joint space distances or shape or signal intensity.
The readers were able to correctly identify symptomatic patients with good interrater reliability (kappa 0.5, sensitivity and specificity 0.87-0.93), positive (LR+= 6.7-7.2) and negative likelihood ratios (LR-=0.15).
Conclusion: Contrary to recent publications, we could demonstrate differences between asymptomatic and symptomatic subjects showing the latter to have larger joints and more signs of degeneration.
One can conclude from the strong LR+ and LR- values that MRI is a useful investigation to rule in or rule out facet pain.