Estimating pedicle screw fastening strength via a virtual templating platform for spine surgery planning: a retrospective preliminary clinical demonstration

Traditional 2D images provide limited use for accurate planning of spine interventions, due to their inability to display the complex 3D spine anatomy and proximity of nerve bundles and vascular structures that must be avoided during the procedure. We have developed a platform for spine surgery planning that employs standard of care 3D preoperative images and enables oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating and placement of virtual pedicle implants into the patient-specific computed tomography data. Here we propose a combined surrogate metric – the fastening strength – to provide estimates of the optimal implant selection and trajectory based on implant dimension and bone mineral density (BMD) of the displaced bone substrate. We conducted a retrospective clinical study based on pre- and post-operative data from four patients who underwent procedures involving pedicle screw implantation. We assessed the retrospective plans against the post-operative imaging data according to implant dimension, mean voxel intensity of implant trajectory, and fastening strength and showed consistency between the proposed plans and the post-operative procedure outcome. Our preliminary studies have demonstrated the feasibility of the platform in assisting the surgeon with the selection of appropriate size implant and trajectory that optimises fastening strength, given the intrinsic vertebral geometry and BMD.