Do Modic changes contribute to lumbar instability or other way around? A retrospective study based on their types, extents, and affected lumbar segments

BACKGROUND: Which types of Modic changes (MCs) and whether or how specific factors associated to MCs work on lumbar instability have yet to be well understood. The purpose of this study was to investigate the influences of the types of MCs, the extent of MCs lesion involvement, and different lumbar levels involved by MCs on lumbar instability. METHODS: This retrospective study included 263 adult subjects with MCs who underwent lumbar X-ray examinations in the neutral, flexion, and extension positions. All patients who met our inclusion criteria were examined with 1.5 Tesla magnetic resonance units. Two experienced authors with more than three-year clinical experience independently evaluated and measured the subjects’ radiographic images. The subgroup analysis was performed to detect the differences in subjects’ baseline characteristics and lumbar segmental motions among three types of MCs, the extent of MCs lesion involvement and different lumbar levels involved by MCs. RESULTS: There was a statistical difference in body mass index (BMI) between different involvement extent of MCs (p < 0.01), indicating that the subjects with high BMI are more likely to develop severe MCs. The subjects with Modic type 1 change (MC1) had a significant increase in lumbar angular motion than those with Modic type 2 change (MC2) and Modic type 3 change (MC3) (p < 0.01) and compared with MC3, a significant increase in lumbar translation motion was detected in subjects with MC1 and MC2 (p < 0.01). While, angular motion decreased, translation motion increased significantly as the extent of MCs lesion involvement aggravated (p < 0.01). However, there were no statistical differences in lumbar angular and translation motions between different lumbar levels involved by MCs (p > 0.05). CONCLUSIONS: Higher BMI might be a risk factor for the development of severe MCs. MC1 and MC2 significantly contribute to lumbar instability. The extents of MCs lesion involvement are strongly associated with lumbar instability. However, different lumbar levels involved by MCs have little effect on lumbar stability.