Optimal surgical planning guidance for lumbar spinal fusion considering operational safety and vertebra-screw interface strength

Background An optimized pre-operative planning framework for lumbar spinal fusion was proposed, which augmented a novel functionality of suggesting optimal insertion trajectories and the screw size, considering operational safety and vertebra–screw interface strength, autonomously. Methods Based on an accurate 3D pedicle model with pre-operative computed tomography (CT) data, the framework begins with safety margin estimation for each potential insertion trajectory, followed by procedures to collect a set of insertion trajectories satisfying the operation safety objective. Among the trajectory candidates, the insertion trajectory, which maximized the insertable depth of a pedicle screw into the vertebral body, was then chosen as optimal, because the insertable depth enhanced the strength of the screw–vertebra interface. The radius of a pedicle screw was chosen as 70% of the pedicle radius. Results This framework has been tested on 176 spinal pedicles of 20 patients requiring spinal fusion. It was successfully applied, resulting in an average success rate of 100% and a final safety margin of 2.1 ± 0.2 mm. Planning accuracy and usefulness of the proposed surgical planner show significant differences compared with a conventional manual planner. Conclusion We can expect that the derived conservative safety margin mitigates screw misplacement or pedicle breach, despite potential errors induced during registrations or intraoperative screw insertion. Copyright © 2012 John Wiley & Sons, Ltd.