Preoperative Computed Tomography Angiography of Pre-lumbar Iliac Vessels: Anatomical Variations and Implications for Anterior Lumbar Surgery

Objective This study aimed to evaluate the anatomical variations of pre-lumbar iliac vessels using computed tomography angiography (CTA) to provide detailed vascular anatomical guidance for anterior surgical approaches to the lower lumbar spine. Methods A retrospective analysis was conducted on abdominal CTA images from 200 patients (100 males and 100 females). The following parameters were assessed: (1) distribution of the aortic bifurcation (AB) and common iliac vein confluence (CIV); (2) distance from the vertex of the angle between the left common iliac vein (LCIV) and right common iliac artery (RCIA) to the superior endplate of the L5-S1 disc; and (3) distances between the medial borders of the LCIV and RCIA at the superior and inferior endplates of the L5-S1 disc. The areas of the "iliac vascular triangle" and "L5-S1 surgical window" were calculated. Results The AB was most frequently observed at the L4 vertebral level (64%), whereas the CIV was primarily located at L4 (42%) and the L4-L5 disc level (40%). The aortic bifurcation angle measured 51.01°±9.24° in males and 50.51°±7.92° in females. The CIV confluence angle was 58.82°±11.81° in males and 62.47°±12.46° in females. The angle between the LCIV and RCIA was 64.92°±12.07° in males and 68.73°±13.87° in females. When the CIV was situated at L4, L4-L5, or L5, both the "iliac vascular triangle" and "L5-S1 surgical window" areas exhibited a progressive reduction in size across genders. Conclusion Significant variations were observed in the positions of the AB and CIV. A CIV confluence at or above the L4-L5 disc level generally affords a sufficient vascular safety zone for anterior L5-S1 surgical procedures, whereas a confluence at L5 may present an inadequate zone. Preoperative CTA is essential for evaluating vascular anatomy and facilitating safe anterior surgical planning.