Background and Objectives: Although adult spinal deformity (ASD) surgery brought about the improvement of quality of life in patients, it accompanied with a high invasiveness of surgery and several complications. Specifically, mechanical complications of rod fracture, instrumentation failures, and pseudarthrosis are still unsolved issues. To better improve these problems, the oblique lateral interbody fusion at L5/S1 (OLIF51) was introduced since 2015 in my institution. The objective of this study was to compare the clinical and radiographic outcomes of anterior-posterior combined surgery for ASD between the use of OLIF51 versus transforaminal interbody fusion (TLIF) at L5/S1. Materials and Methods :A total of 117 ASD patients received anterior-posterior correction surgeries either use of OLIF51 (35 patients) or L5/S1 TLIF (82 patients). In both groups, L1-5 OLIF and minimally invasive posterior procedures of hybrid or circumferential MIS were employed. The sagittal and coronal spinal alignment and spino-pelvic parameters are recorded preoperatively and at follow-up. The quality of life parameters and visual analogue scale were evaluated as well as surgical complications at follow-up. Results: The average follow-up period was thirty months (13-84). The average fused segments were eight (4-12). The operation time and estimated blood loss were significantly smaller in OLIF51 that those in TLIF. The PI-LL mismatch, LLL, L5/S1 segmental lordosis, and L5 coronal tilt were significantly better in OLIF51 than TLIF. The complication rate was statistically equivalent between two groups. Conclusion: The introduction of OLIF51 for adult spine deformity surgery led to the decrease of operation time and estimated blood loss as well as the improvement of sagittal and coronal correction when compared to TLIF.

Background and objectives: As the oblique lateral interbody fusion at L5/S1 (OLIF51) and lateral corridor approach (LCA) have gained popularity, the understanding of precise vascular structure at L5/S1 level is indispensable. The objectives of this study were to investigate the vascular anatomy at L5/S1 level, and to compare the movement of vascular tissue between supine and lateral decubitus position using the intraoperative enhanced CT and MRI. Materials and Methods: A total of 43 patients who underwent either OLIF51 or LCA were investigated with the average age at surgery of 60.4 (37-80) years old. The preoperative MRI was taken to observe axial and sagittal anatomy of vascular position under supine position. The intraoperative vein-enhanced CT was taken just before incision in the right decubitus position, and compared to supine MRI anatomy. The iliolumbar vein appearance and its types were also classified. Results: The average vascular window allowed for OLIF51 was 22.8 mm and 34.1 mm at either L5 caudal endplate or S1 cephalad endplate level, respectively. It allowed for LCA was 14.2 mm and 12.6 mm at either level, respectively. The left common iliac vein moved 3.8 mm and 6.9 mm to right direction at either level from supine to right decubitus position, respectively. The bifurcation moved 6.3 mm to caudal direction from supine to right decubitus. The iliolumbar vein was located at 31 mm lateral from midline, and MRI detection rate was 52%. Conclusions: The precise measurement of vascular anatomy indicated that OLIF51 approach was the standard minimally invasive anterior approach for L5/S1 disc level compared to LCA, however, there were many variations in quantitative anatomy as well as significant vascular movements between supine and right decubitus position. In the clinical setting of OLIF51 and LCA surgeries, the careful preoperative evaluation and intraoperative 3D imaging are recommended for the safe and accurate surgery.