Critical analysis for a safe design of 3D printed Patient-Specific Surgical Guides (PSSG) for pedicle screw insertion in spinal deformities

Abstract Pedicle screws are used in spinal fusion for the stabilisation of the spine through a posterior approach. In spinal deformities, such as scoliosis, pedicle screw placement is especially challenging due to vertebral rotation and landmark distortion. Conventional surgical procedures such as Free-hand screw insertion mainly rely on surgeon experience and anatomical landmarks. Image- and robot-guided pedicle screw insertion can improve placement accuracy but require exposure to ionising radiation. Studies of 3D-printed patient-specific surgical guides (PSSG) have shown similar accuracy rates and reduced intra-operative radiation. Nevertheless, the guide design and workflow of these devices present significant challenges. This manuscript presents a narrative review of the literature regarding the analysis of designs, manufacturing, and technical considerations for patient-specific screw guides (PSSG). We focus on the analysis of imaging criteria, design variables (including spinal levels, anatomical landmarks and guiding tools), manufacturing technology, 3D-printing technology and validation studies (ex vivo and in vivo). We also discuss the clinical and economic benefits of PSSGs and provide further dialogue on the limitations and requirements for better adoption of this technology in future. Compared to Free-hand pedicle screw placement, we find that PSSGs show consistently superior placement accuracies and when compared to image and robot-guided technologies, their use requires less radiation exposure, shorter operative times and economic benefits. The guides are of additional use in cases of complex spinal deformities, especially if guided technologies are not available.