Association Between Spinopelvic Alignment and MRI-Based Stenosis Severity According to Schizas Grade in Degenerative Lumbar Spinal Stenosis

Aim: Degenerative lumbar spinal stenosis (DLSS) is a common age-related disorder, but the relationships between MRI-defined stenosis severity, local radiological findings, and pelvic orientation remain unclear. We hypothesized that pelvic tilt would increase with Schizas grade.Materials and Methods: This single-center retrospective cross-sectional study included 120 consecutive patients older than 50 years with clinically and radiologically diagnosed DLSS who underwent lumbar MRI and standardized standing lateral radiography. The index stenotic level was defined as the level with the highest Schizas grade. Ligamentum flavum thickness, average disc height, and wedge index were measured at the same index level. Spinopelvic parameters included pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, and pelvic incidence–lumbar lordosis mismatch. Secondary comparisons and correlations were assessed using Benjamini–Hochberg false-discovery-rate correction. Adjusted associations with higher Schizas grade were examined using ordinal logistic regression.Results: Seventeen patients had grade A, 25 grade B, 33 grade C, and 45 grade D stenosis. L4–L5 was the most common index level, and 74 patients (61.7%) had multilevel stenosis. Index-level ligamentum flavum thickness increased across Schizas grades and remained significant after multiplicity correction. Average disc height and wedge index decreased with increasing severity, but these findings were weaker and exploratory. Pelvic tilt showed a weak positive correlation with Schizas grade. In the adjusted model, greater ligamentum flavum thickness, older age, and higher pelvic tilt were associated with higher Schizas grade. The pelvic tilt association was small, and model explanatory capacity was modest.Conclusions: Greater index-level ligamentum flavum thickness showed the most robust association with higher Schizas grade. Pelvic tilt was weakly associated with stenosis severity, but the cross-sectional design does not establish a compensatory response caused by stenosis. These findings are hypothesis-generating and require prospective validation.