Experience with freehand thoracic pedicle screw placement is well described in the literature. Published techniques rely on various starting points and trajectories for each level or segment of the thoracic spine. Furthermore, few studies provide specific guidance on sagittal and axial trajectories. The goal of this study was to propose a uniform entry point and sagittal trajectory for all thoracic levels during freehand pedicle screw placement and determine the accuracy of this technique.
The authors retrospectively reviewed postoperative CT scans of 33 consecutive patients who underwent open, freehand thoracic pedicle-screw fixation using a uniform entry point and sagittal trajectory for all levels. The same entry point for each level was defined as a point 3 mm caudal to the junction of the transverse process and the lateral margin of the superior articulating process, and the sagittal trajectory was always orthogonal to the dorsal curvature of the spine at that level. The medial angulation (axial trajectory) was approximately 30° at T-1 and T-2, and 20° from T-3 to T-12. Breach was defined as greater than 25% of the screw diameter residing outside of the pedicle or vertebral body.
A total of 219 thoracic pedicle screws were placed with a 96% accuracy rate. There were no medial breaches and 9 minor lateral breaches (4.1%). None of the screws had to be repositioned postoperatively, and there were no neurovascular complications associated with the breaches.
It is feasible to place freehand thoracic pedicle screws using a uniform entry point and sagittal trajectory for all levels. The entry point does not have to be adjusted for each level as reported in existing studies, although this technique was not tested in severe scoliotic spines. While other techniques are effective and widely used, this particular method provides more specific parameters and may be easier to learn, teach, and adopt.