Abstract / Summary
Abstract Purpose The vein-free vascular corridor is an important anatomical factor influencing anterior access to the lumbosacral junction. This study aimed to characterize iliac venous anatomy at L5–S1 and its relationship with pelvic incidence (PI), focusing on corridor configuration and dimensions. Methods A consecutive cohort of 160 adults with standing full-spine radiographs and lumbosacral magnetic resonance imaging was analyzed. On axial images at L5–S1, the relationship between the iliac veins and anterior disc was assessed using a five-type classification of the vein-free vascular corridor. Corridor dimensions were quantified as the interiliac distance relative to total disc width. Associations with PI were assessed using linear and ordinal logistic regression, adjusted for age and sex. Results Mean age was 56.8 ± 15.2 years and mean PI was 52.8 ± 12.4°. Types III–IV accounted for 79.4% of cases. Disc window percentage increased progressively across vascular types, from 0% in Type 0 to 79.8% in Type IV (p < 0.001). PI was positively associated with disc window percentage, and this remained significant after adjustment for age and sex (adjusted β = 0.45 percentage points per degree; 95% CI 0.13–0.77; p = 0.006). Increasing PI was also associated with higher vascular corridor categories (adjusted OR 1.028 per degree; 95% CI 1.002–1.054; p = 0.037). Conclusion Pelvic incidence is associated with iliac venous anatomy at L5–S1. Increasing PI was associated with a wider vein-free vascular corridor and with progressively higher corridor categories, supporting a relationship between pelvic morphology and the transverse configuration of the iliac veins.