Imaging severity stratification of thoracic disc herniation and its association with neurological dysfunction: a retrospective cohort study

Purpose To develop a practical imaging severity stratification for thoracic disc herniation (TDH) combining canal occupation ratio and the axial ABC-0/1/2 morphology, and to evaluate associations with neurological dysfunction and postoperative recovery. Methods In a retrospective single-network TDH cohort (1998–2025), canal occupation (%) was measured on axial CT/MRI and axial morphology was classified as ABC-0/1/2. Primary outcomes were preoperative bladder dysfunction and severe myelopathy; secondary outcomes included gait disturbance and recovery. Multivariable logistic regression adjusted for age, sex, calcification, and multilevel disease. Results Of 1129 surgical TDH cases, 536 had complete axial classification and canal measurements. Preoperative gait disturbance occurred in 42.5% and bladder dysfunction in 23.2%. Canal occupation increased from class A to C (38.0% to 47.5%). Each 10% increase in canal occupation was independently associated with bladder dysfunction (OR 1.11, 95% CI 1.01–1.22; p = 0.024), while calcification was associated with severe myelopathy (OR 1.50, 95% CI 1.03–2.19; p = 0.037). The bladder-dysfunction model showed modest discrimination (AUC 0.62). Among patients with baseline deficits and follow-up, recovery occurred in 72.6% (gait) and 83.6% (bladder). Conclusion A combined canal-occupation and ABC-0/1/2 framework provides an interpretable mapping to neurological dysfunction in TDH and may support preoperative risk stratification and counseling.