Zdravniški Vestnik (Feb 2017)
Determination of the pedicle screw size and trajectory in CT images of thoracic spinal deformities: a comparison between manual and computer-assisted preoperative planning
Abstract
Background: Vertebral fixation by pedicle screw placement is the most frequently applied fixation technique in spinal surgery. In this retrospective study we present a comparison of manual and computer-assisted preoperative planning of pedicle screw placement in three-dimensional (3D) computed tomography (CT) images of deformities in the thoracic spine.Methods: Manual planning of the pedicle screw size and trajectory was performed by two orthopedic surgeons using a dedicated software for preoperative planning of surgical procedures, while computer-assisted planning was performed by automated image processing and analysis techniques through the optimization of screw fastening strength. The size (diameter and length) and trajectory (pedicle crossing point, inclination in the sagittal plane, inclination in the axial plane) were obtained for 316 pedicle screws from 3D CT images of 17 patients with thoracic spinal deformities.Results: the analysis of pedicle screw parameters, obtained by two manual and one computer-assisted planning, indicated a statistically significant difference in the screw size (p < 0.05) and trajectory (p < 0.001). Computer-assisted planning proposed wider (p < 0.05) and longer (p < 0.001) screws with a higher (p < 0.001) normalized fastening strength.Conclusions: The comparison revealed consistency between manual and computer-assisted planning of the pedicle screw size and trajectory, except for the screw inclination in the sagittal plane, as manual planning followed more the straight-forward while computer-assisted planning followed more the anatomical insertion technique. While being faster, more repeatable and more reliable than manual planning, computer-assisted planning was also linked with a higher screw fastening strength and consequently a higher screw pull-out strength.
