Lumbar spine: Reliability of MR imaging findings

Purpose: To characterize the inter- and intraobserver variability of qualitative, non-disk contour degenerative findings of the lumbar spine at magnetic resonance (MR) imaging. Materials and Methods: The case accrual method used to perform this institutional review board-approved, HIPAA-compliant retrospective study was the random selection of 111 interpretable MR examination cases of subjects from the Spine Patient Outcomes Research Trial. The subjects were aged 18-87 years (mean, 53 years ± 16 [standard deviation]). Four independent readers rated the cases according to defined criteria. A subsample of 40 MR examination cases was selected for reevaluation at least 1 month later. The following findings were assessed: spondylolisthesis, disk degeneration, marrow endplate abnormality (Modic changes), posterior anular hyperintense zone (HIZ), and facet arthropathy. Inter-and intraobserver agreement in rating the data was summarized by using weighted κ statistics. Results: Interobserver agreement was good (k = 0.66) in rating disk degeneration and moderate in rating spondylolisthe- sis (k = 0.55), Modic changes (k = 0.59), facet arthropathy (κ = 0.54), and posterior HIZ (κ = 0.44). Interob-server agreement in rating the extent of Modic changes was moderate: κ Values were 0.43 for determining superior anteroposterior extent, 0.47 for determining superior craniocaudal extent, 0.57 for determining inferior antero- posterior extent, and 0.48 for determining inferior cranio- caudal extent. Intraobserver agreement was good in rating spondylolisthesis (κ = 0.66), disk degeneration (κ = 0.74), Modic changes (κ = 0.64), facet arthropathy (κ = 0.69), and posterior HIZ (κ = 0.67). Intraobserver agreement in rating the extent of Modic changes was moderate, with κ values of 0.54 for superior anteroposterior, 0.60 for inferior anteroposterior, 0.50 for superior craniocaudal, and 0.60 for inferior craniocaudal extent determinations. Conclusion: The interpretation of general lumbar spine MR characteristics has sufficient reliability to warrant the further evaluation of these features as potential prognostic indicators.