Automated Pedicle Screw Size and Trajectory Planning by Maximization of Fastening Strength

Spinal fusion combined with vertebral fixation through pedicle screw placement is the preferred surgical treatment for several spinal deformities. The accuracy of pedicle screw placement is directly related to the surgical outcome, however, manual planning of screw size and trajectory is time-consuming, while automated approaches do not take into account the screw fastening strength. We propose a novel automated method for optimal planning of pedicle screw size and trajectory that takes into account both geometric (i.e. morphometry) and anatomical (i.e. bone mineral density) properties of vertebrae to maximize the screw fastening strength. The size and trajectory of 61 pedicle screws, determined by the automated method in computed tomography images of nine patients, were in high agreement with preoperative manual plans defined by a spine surgeon (mean difference of 0.6mm in diameter, 4.0mm in length, 1.7mm in pedicle crossing, and (6.1.) in screw insertion angles), and an increased fastening strength was observed for 50 cases (82%).