Kinematics of an intervertebral disc with type 1 Modic change: mechanical and non-mechanical causes

BackgroundType 1 Modic change (MC) is associated with chronic low back pain and attributed to segmental instability. However, the relationship between type 1 MC and segmental instability is unclear. This study sought to clarify the role of mechanical abnormalities in type 1 MC.MethodReview of magnetic resonance images obtained for 727 patients over a 1-year period at our institution revealed 161 cases of type 1 MC. In 86 of these, the following indicators of mechanical abnormality could be evaluated on dynamic radiographs: segmental scoliosis (> 5°), forward slippage (> 1%), and posterior disc opening in flexion. Patients with one or more of these abnormalities were allocated to a mechanical group (n = 62, 70%) and those with no abnormality to a non-mechanical group (n = 26, 30%). The Pfirrmann grade of disc degeneration at the affected level was compared between the groups.ResultsSegmental scoliosis, slippage, and posterior opening was observed in 34, 21 and 37 cases, respectively. Severe disc degeneration (grade IV or V) was present in 43 cases (69%) in the mechanical group and in 12 cases (46%) in the non-mechanical group; the difference was statistically significant ( p = 0.04).ConclusionWe propose that there are mechanical and non-mechanical variants of type 1 MC.