Robotic-assisted Spinopelvic Fusions using S2 Alar Iliac Screws

Abstract Background: The S2 alar iliac (S2AI) screw is currently the preferred Zone 3 pelvic anchor in spinopelvic fusions. It offers significant resistance to pull out, is in line with the lumbosacral pedicle screws due to its recessed entry point, and has less irritation due to implant prominence. Robotic assistance in spine surgery allows the planning and execution of precise trajectories even in the presence of altered anatomy. We describe the technique of placement of S2AI screws in long-segment spinal fixation using the MazorX stealth edition (MXSE). Material and Methods: Sixteen robotic-assisted S2AI screws were inserted in eight patients with fusions to the pelvis. The screws were inserted using the scan-and-plan workflow of the MXSE. All S2AI screws were analyzed using postoperative O-arm scans. The time taken for the insertion of the S2AI screws was noted. The mean craniocaudal and mediolateral angulation during screw insertion was noted. The mean radiation exposure was also noted. Results: The most cranial upper instrumented vertebra (UIV) was T8 and required two sets of O-arm scans, and the most caudal UIV was L4 in which a single scan was used. The mean time for S2AI screw insertion was 3.1 min. The mean radiation dose to the patient was 48.7 mGy. The mean medial angle for insertion on the axial view was 37°, and the mean caudal angulation on the sagittal view was 17°. All screws were completely within the bone and had no breaches. Conclusions: Robotic assistance provides additional safety and lowers the risk of misplacement of the S2AI screw with reduced radiation to the surgeon.