Laparoscopic anterior lumbar interbody fusion at L4-L5 - An anatomic evaluation and approach classification

Study Design. An anatomic classification system was devised on the basis of operative reports and preoperative magnetic resonance imaging or computerized tomography from 139 patients who underwent laparoscopic anterior lumbar interbody fusion involving L4-L5. Objective. To devise a classification system for laparoscopic exposure of the L4-L5 disc space that would allow prediction of the safest approach for any given vascular configuration. Summary of Background Data. The laparoscopic technique has gained acceptance at L5-S1 but has been less successful at L4-L5. The vascular bifurcation and the variability of the anatomy have led to difficulties with exposure. Methods. Data were collected on 139 patients undergoing laparoscopic anterior lumbar interbody fusion involving the L4-L5 disc space. Operative notes and preoperative magnetic resonance imaging and computed tomography scans were reviewed, and a classification system was devised based on the aortic bifurcation and confluence of the left iliac vein with the vena cava. Three variations were identified. Complications, particularly ejaculatory dysfunction, were described. Results. Three classification categories were described. Twenty-five patients (18%) were classified as category A (above the bifurcation of both vessels), 52 patients (37%) were classified as category 8 (below the bifurcation of both vessels), and 51 patients (37%) were classified as category C (between the left iliac artery and vein). There were 8 (5.8%) intraoperative and 17 (12.2%) postoperative complications. Ejaculatory dysfunction constituted the majority of the postoperative complications, representing 16% of the male population, The incidence of ejaculatory dysfunction correlated with exposure from the left side of the aorta or the left iliac artery. For two-level fusions from L4 to S1, the incidence of ejaculatory dysfunction was 63% for category A but 0% for categories 8 and C. An alternative approach was suggested for category A: exposing the disc space between the aorta and vena cava. Conclusion. The laparoscopic approach to L4-L5 is complicated by the variability of the vascular anatomy encountered during the exposure. Routine magnetic resonance imaging or computed tomography can be used to classify the vascular anatomy and plan the optimal approach. Avoiding the left side of the aorta or the left iliac artery may minimize the risk of ejaculatory dysfunction.