Vascular Anatomy in the Lumbar Spine Investigated by Three-Dimensional Computed Tomography Angiography: The Concept of Vascular Window

Objective To report an in vivo anatomic evaluation of prevertebral vessels in the lumbar spine using three-dimensional (3D) computed tomography (CT) angiography and to develop the concept of vascular window for surgical access to L4-5 and L5-S1 disks. Methods In 146 patients who were scheduled for anterior lumbar spine surgery, 3D CT angiography was performed preoperatively. Spinal disorders included degenerative disk disease ( n = 120) and low-grade spondylolisthesis ( n = 26). 3D reconstructions were obtained using the volume-rendering technique. Level of aortic bifurcation and iliocavum confluence, presence of the ascending iliolumbar vein, presence of the central sacral vessels, and anatomic variations were analyzed. A vascular window at L5-S1 was defined as the “free vascular” area for the anterior part of the L5-S1 disk. A vascular window at L4-L5 was defined as the “free vascular” area for the left anterolateral part of the L4-5 disk. Results The level of aortic bifurcation was most often observed at L4 (64%). The iliocavum confluence occurred most frequently at L5 (44%). The iliolumbar ascending vein and central sacral vessels were identified in 84% and 72% of cases. Five (3.5%) anatomic variations were noted: right internal iliac vein draining into the left common iliac vein in two cases and tortuous vessels in three cases. A vascular window was measured to 34.5 mm ± 12 at L5-S1 and to 23 mm ± 8 at L4-L5. The vascular window was