Assessment of Injury Incidence and Radiological Outcomes in OLIF L5/S1: Iliac Bifurcation Versus Prepsoas Approach.

Objective: The oblique lateral interbody fusion (OLIF) technique at the L5-S1 segment can be approached via iliac vessel bifurcation or prepsoas approaches, depending on vascular anatomy and iliac crest height. This study aims to compare clinical and radiological outcomes between these two surgical methods. Methods: This single-center retrospective study analyzed 58 patients undergoing OLIF surgery at L5-S1 from January 2020 to December 2023. Patients were divided into bifurcation (n=36) and prepsoas (n=22) approach groups. Outcomes measured included radiological parameters (anterior/posterior disc heights, foraminal height, disc angle), clinical parameters (Visual Analog Scale for leg/back pain, Oswestry Disability Index), and complications. Results: No significant differences were observed preoperatively between groups. Postoperatively, the prepsoas group showed significantly increased posterior disc and foraminal heights, whereas the bifurcation group had a significantly greater disc angle. Leg pain scores improved significantly more in the bifurcation group at four months. Complications were comparable, though the prepsoas approach was associated with higher incidences of contralateral root and endplate injuries. Conclusion: Both surgical approaches are safe and effective. The bifurcation corridor approach using an anterior lumbar interbody fusion cage optimizes segmental angulation, while the prepsoas corridor approach is more effective for increasing foraminal height. Careful preoperative anatomical evaluation is essential for selecting the optimal surgical approach.