In OLIF, the patient was placed in the right decubitus position. A transverse incision of approximately 4 cm was made on the skin in the left lateral region of the abdomen. After dissection of the external oblique, internal oblique, and transverse abdominal muscles, the retroperitoneal space was accessed by blunt dissection through the retroperitoneal fat tissue. The psoas muscle was retracted posteriorly. The targeted intervertebral disc space was exposed, and the tubular retractor system was set. Under direct visualization, a discectomy was performed and both cartilaginous endplates were thoroughly removed, and the polyetheretherketone (PEEK) cage with allograft was placed in the disc spaces. After performing OLIF, percutaneous screw insertion to the cephalad and caudal vertebrae was performed in the lateral position without position change using an intraoperative three-dimensional computed tomography (3D-CT)-based navigation system (O-arm; Medtronic, Minneapolis, MN, USA). We used the modified cortical bone trajectory (CBT) screw technique as previously reported (Fig. 2) [18 (link)]. Rods were then placed. This series of procedures were performed without intraoperative neuromonitoring. After the surgery, the patient was allowed to walk with a hard brace and was required to wear the brace for at least 2 months after the surgery (Fig. 3).