Introduction: Lateral intervertebral fusion of the lumbar spine is associated with the risk of injury to large blood vessels, their branches, and venous malformations.

Objective: To evaluate the anatomy that poses a risk of vascular injury in lateral intervertebral fusion using preoperative contrast-enhanced computed tomography (CT).

Materials: Forty-six patients who underwent contrast-enhanced CT prior to lateral intervertebral fusion at our institution were included, and major arteries and veins were evaluated on horizontal section images at each vertebra from L1/2-L4/5. The presence or absence of lumbar artery branches running longitudinally across the intervertebral disk was evaluated in each vertebral segment. Venous malformations were evaluated for (a) duplicated vena cava, (b) running of the left common iliac vein branch outside the common iliac artery, and (c) dilatation of the ovarian vein or spermatic cord vein.

Results: Major arteries traveling in Zones 1-4 according to Moro et al.'s evaluation method were found in 5 cases (11%) in L1/2, 3 cases (7%) in L2/3, 2 cases (4%) in L3/4, and 5 cases (11%) in L4/5. Major veins were found in 6 cases (13%) in L1/2, 16 cases (35%) in L2/3, 37 (80%) in L3, 37 (80%) in L1/2, 16 (35%) in L2/3, 39 (85%) in L3/4, and 39 (85%) in L4/5. Longitudinal disk traversal of the lumbar artery branch was present in 1 case (2%) in L3/4 and 15 (33%) in L4/5. Venous malformations were found in (a) 0 (0%), (b) 4 (9%), and (c) 3 (7%) patients, respectively.

Conclusions: Major arteries and veins may be present within the operative range at any elevation from L1/2 to L4/5, and segmental arteries may traverse near the intervertebral disk at L3/4 and L4/5. Venous malformations should also be assessed preoperatively.