%0 Journal Article %A Cyrill Dennler %A Nico Akhavan Safa %A David Ephraim Bauer %A Florian Wanivenhaus %A Florentin Liebmann %A Tobias Götschi %A Mazda Farshad %T Augmented Reality Navigated Sacral-Alar-Iliac Screw Insertion %D 2021 %R 10.14444/8021 %J International Journal of Spine Surgery %P 8021 %X Background Sacral-alar-iliac (SAI) screws are increasingly used for lumbo-pelvic fixation procedures. Insertion of SAI screws is technically challenging, and surgeons often rely on costly and time-consuming navigation systems. We investigated the accuracy and precision of an augmented reality (AR)–based and commercially available head-mounted device requiring minimal infrastructure.Methods A pelvic sawbone model served to drill pilot holes of 80 SAI screw trajectories by 2 surgeons, randomly either freehand (FH) without any kind of navigation or with AR navigation. The number of primary pilot hole perforations, simulated screw perforation, minimal axis/outer cortical wall distance, true sagittal cranio-caudal inclination angle (tSCCIA), true axial medio-lateral angle, and maximal screw length (MSL) were measured and compared to predefined optimal values.Results In total, 1/40 (2.5%) of AR-navigated screw hole trajectories showed a perforation before passing the inferior gluteal line compared to 24/40 (60%) of FH screw hole trajectories (P < .05). The differences between FH- and AR-guided holes compared to optimal values were significant for tSCCIA with −10.8° ± 11.77° and MSL −65.29 ± 15 mm vs 55.04 ± 6.76 mm (P = .001).Conclusions In this study, the additional anatomical information provided by the AR headset and the superimposed operative plan improved the precision of drilling pilot holes for SAI screws in a laboratory setting compared to the conventional FH technique. Further technical development and validation studies are currently being performed to investigate potential clinical benefits of the AR-based navigation approach described here.Level of Evidence 4. %U http://www.ijssurgery.com/content/ijss/early/2021/02/16/8021.full.pdf