Preoperative 3D CT Planning for Cortical Bone Trajectory Screws: A Retrospective Radiological Cohort Study.

BACKGROUND

Pedicle screw instrumentation is a standard procedure in lumbar spinal fusion. The cortical bone trajectory (CBT) screw is an alternative technique, less invasive but harder to perform. The identification of the entry point and the appropriate direction can be tricky especially to the surgeons just at the beginning. Therefore, the aim of this study is to evaluate the reliability of preoperative computed tomography (CT) planning in the CBT screw placement.

METHODS

We retrospectively evaluated 82 patients who underwent a single-level posterior lumbar arthrodesis with CBT screws. The correct entry point and the best trajectory were identified on a 3-dimensional (3D) multiplanar reconstruction CT view. The concordance between achieved and planned trajectories was assessed on a postoperative CT.

RESULTS

A total of 328 screws was positioned. The average entry point distance from the target was 1.1 mm (standard deviation, ±0.15 mm). In 301 screws (91.8%), the obtained trajectory differed no more than 2° from the planned one. No screws misplaced or new neurological deficit was recorded.

CONCLUSIONS

The CBT screw placement is a great alternative to the pedicle screw. Accurate preoperative 3D planning is useful to predict the entry point and the direction with accuracy similar to navigation systems, avoiding its costs and technical difficulties. The 3D CT planning is helpful in the customization of spine surgery, and the results underline the radiological reliability of this technique.