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

Abstract

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. 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. 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. 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.