Statistical shape modeling of MRI-based morphological response of lumbar intervertebral discs to a unilateral side lying spinal rotation mobilization

Objectives: The acute response of lumbar intervertebral discs (IVD) to spinal rotation mobilization (SRM) is poorly understood. We evaluated sustained morphological changes in lumbar IVDs following a rotation mobilization commonly used to relieve discogenic pain. Design: In this cross-sectional study, five asymptomatic participants underwent MRI of the lumbar spine before and after 2 min of sustained passive unilateral SRM. Pre-SRM acquisition was completed twice, repositioning between acquisitions to assess test-retest reliability. Five lumbar IVDs per participant were segmented independently by two raters, and compared between timepoints using Dice similarity coefficients (DSC). We used statistical shape modeling (SSM) to assess magnitude and direction of shape changes as defined by principal component analysis (PCA). Primary analysis evaluated the PCA scores from the SSM models of all IVDs; secondary analysis assessed each IVD individually. Results: Significant changes were observed in IVD shape following SRM (p 0.9). Conclusions: SRM induces measurable, direction-specific changes in healthy IVDs. Future research should evaluate symptomatic IVDs, examining relationships between morphology, symptoms, and therapeutic parameters.