Abstract
Recent progress in 3-dimensional (3D) computer technology has enabled spinal surgeons to make accurate diagnosis and detailed preoperative planning. Spine models in actual size can also be made by 3D plastic printer so that the surgeons can perform preoperative simulations of all the procedures. In this article, the authors introduce two novel applications of this technology : a pedicle screw guiding method for cervical/thoracic spine and order-made titanium spinal stabilization implants. For the screw guiding method, preoperative bone images of the computed tomography (CT) scans were analyzed using 3D multi-planar imaging software and the trajectories of the screws were the planned accordingly. Plastic templates with screw guiding structures were created for each lamina by 3D design and printing technology. Three types of the templates were made for precise multi-step guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Postoperative CT scans showed that the mean deviation of the screws from the planned trajectories was less than 1 mm at the coronal midpoint section of the pedicles. The multi-step, patient-specific screw guide template system is useful for intraoperative pedicle screw navigation. For the production of order-made titanium spinal stabilization implants for instable spinal diseases, bone data were also extracted from CT images, and the implants that cover posterior surface of the lamina were designed with industrial 3D technology. The titanium cover for each lamina was connected with an artificial joint/spring structure, providing stabilization while still preserving intervertebral segmental motions. These order-made implants were printed by a 3D titanium printer, and the physical properties and precision of the products were determined. Animal studies showed excellent kinematic capabilities and long-term safety, and preclinical studies are now ongoing with a grant from Japanese Ministry of Economy, Trade and Industry. Today 3D computer technology is defining an epoch in spinal surgery and many new applications are still to be developed.
