Object: The complexity of the vascular anatomy pertinent to the L4-5 intervertebral disc space has led to difficulties when performing the anterior approach to the lumbar spine. The purpose of the present study was to evaluate the variations of the great vessels to match the imaging-documented axial anatomy with the surgical exposure.
Methods: The authors analyzed data obtained in 223 patients who had undergone mini-open anterior lumbar surgery involving the L4-5 disc. The preoperative magnetic resonance images or computed tomography scans were evaluated by examiners blinded to the surgical approach to determine the vascular configuration. All complications of the procedures were described. Two major variations of the vascular configuration were delineated according to the location of the bifurcation of the inferior vena cava. On images showing the lower margin of the L-4 vertebra, the anatomy in 182 patients (81%) was classified as Type A because the inferior vena cava (IVC) was not bifurcated; in 38 patients (17%) it was classified as Type B because the IVC was bifurcated. Type A could be subdivided into Types A1 and A2 according to whether the aorta was bifurcated (A2) or not (A1) on the same image. The surgical exposure used was above the bifurcations (in Type A) and below the bifurcations (in Type B). The major complications were three venous injuries, and the leading complication was sympathetic dysfunction in 14 patients, which in most cases resolved spontaneously.
Conclusions: Careful preoperative evaluation of the vascular anatomy is essential to conducting successful anterior lumbar surgery. The determination of an appropriate approach can contribute to a reduction of unnecessary vascular retraction and a consequent decrease in vascular complications.