Freehand Pedicle Screw Placement Using a Universal Entry Point and Sagittal and Axial Trajectory for All Subaxial Cervical, Thoracic and Lumbosacral Spines.

Abstract

ObjectiveExisting techniques of freehand pedicle screw placement primarily focus on various entry points with or without axial trajectory. The objective of this paper is to propose a universal entry point and sagittal and axial trajectory for all subaxial cervical, thoracic and lumbosacral spines freehand pedicle screw placements, and to report the results from a single‐surgeon clinical experience with freehand pedicle screw placement.MethodsTwo spine vertebrae specimens and 20 cases of three‐dimensional (3D) reconstructions of spine CT images were used for observation of the entry point and sagittal and axial trajectory. The author retrospectively reviewed a total of 610 consecutive patients who underwent open, freehand pedicle screw fixation using a universal entry point and sagittal and axial trajectory for all subaxial cervical, thoracic and lumbosacral spine placements, during an 8‐year period from January 2010 to December 2017. The junction of the lateral margin of the superior articulating process and the transverse process for the thoracic and lumbosacral spines, or lateral mass for the subaxial cervical spine, was determined. The entry point was chosen at 1 mm, 2 mm, and 3 mm (2 mm on average) caudally and medially to this junction for subaxial cervical, thoracic and lumbosacral spines placements, respectively. Both sagittal and axial trajectories were perpendicular to the sagittal and axial planes of the laminae of the isthmus. Among them, 68 patients underwent postoperative computed tomography (CT) scans, including 26 cervical cases, 19 scoliosis thoracic cases, 10 non‐scoliosis thoracic cases, 8 lumbar cases, and 5 sacral cases. Placements of pedicle screws were assessed using CT data and outcome‐based classifications systems.ResultsAfter placing the iron scurf at the junction of the lateral margin of the superior articulating process and the transverse process, the present universal entry point was located at 1 o'clock or 11 o'clock of the pedicle's axial view. After inserting the 2.5 mm Gram needle or the pedicle virtual pin tracts according to the entry point and sagittal and axial trajectory described above, the presented trajectory was located in the pedicle's axial trajectory as in the described technique. A total of 766 pedicle screws were placed in 68 CT scan patients with a 99% accuracy rate in the non‐kyphoscoliosis group and 92% in the kyphoscoliosis group.ConclusionsFreehand pedicle screw placement based on the universal entry point and sagittal and axial trajectory for all subaxial cervical, thoracic and lumbosacral spines can be performed with acceptable safety and accuracy.