The Association of Modic Changes and MRI Phenotypes of the Lumbar Spine: A Population-Based Study

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Introduction Low back pain is the world's most disabling condition. Modic changes (MC) are associated with low back pain. These changes are spinal phenotypes that represent vertebral endplate and adjacent marrow changes on MRI. MC are classified into three main types (type I, type II, and type III) and mixed types (type I/II and II/III). Due to methodological biases in previous studies, the morphology, involvement of MC, and their association with other spinal phenotypes remain speculative. As such, the aim of this study was to evaluate the relationship of MC with other spinal MRI phenotypes in a large-scale population-based study. Materials and Methods Based on the Hong Kong Disc Degeneration Cohort of Southern Chinese, we assessed the T1- and T2-weighted MRIs of 1,604 subjects (62.4% females; mean age: 49 years) from L1 to S1. The MC assessment included the presence, type, vertical height, and axial area of MC. MC were evaluated as type I, type I/II, type II, type II/III, and type III. Types were regrouped in the analyses as “type I” (types I and I/II) and “type II” (types II and II/III). Very small MC, such as MC in only one sagittal plane, were excluded. Additional imaging phenotype findings were assessed (disc bulges/extrusions, Schmorl nodes, disc degeneration). Disc degeneration was based on the Pfirrmann classification. A degenerative disc disease (DDD) score was tabulated, which represented the global severity of disc degeneration of the lumbar spine. The lumbar spine was further stratified to upper (L1-L4) and lower (L4-S1) regions. Results The prevalence of MC was 24.7% (“type I”: 6.3%, “type II”: 15.5%). Of all MC, 77% were at L4-S1. Subjects with MC were older (mean age: 53 vs. 48 years, p < 0.001) and had higher DDD scores ( p < 0.001). “Type I” MC were more common at lower lumbar levels ( p = 0.021), were less likely to be located only in the anterior region ( p = 0.017), and were more associated with disc bulges/extrusions ( p < 0.001) in comparison to “type II” MC. MC of the lower lumbar levels were not commonly noted only in the anterior region, involved more likely only the left or right endplate and had a higher prevalence of disc bulges/extrusions and disc degeneration in comparison to upper lumbar levels ( p < 0.001). Large MC (≥2/3 of the axial area) were more likely located at lower lumbar levels (83 vs. 73%, p = 0.001) and had a higher prevalence of disc bulge/extrusion (83 vs. 72%, p = 0.001) and Schmorl node at the affected level (52 vs. 39%, p < 0.001) compared with smaller MC. Conclusion Based on one of the largest population-based studies, our findings strengthen the belief that MC are clearly associated with disc pathology, such as disc degeneration, disc bulges/extrusions, and endplate abnormalities (e.g., Schmorl nodes). MC type- and level-related findings in relation to additional MRI phenotypes were also identified. This study further refines the phenotypic classification of MC, which if standardized can have immense utility in studies assessing the role of biomarkers (e.g., genetics) in relation to clinically relevant spinal changes. Acknowledgments The study has been supported by AOSpine Research Network Exchange Award. Disclosure of Interest None declared