Optimization of Paravertebral Foramen Screw Placement: A Stepwise Approach Considering O-arm Navigation Errors: Technical Note and Case Series.

Objective: Paravertebral foramen screws (PVFSs) have been developed for better pullout strength than lateral mass screws do and lower the risk of vertebral artery and nerve injury than do pedicle screws. While the original method involves insertion using lateral fluoroscopy, its reliability may be limited. This report is the first to assess the accuracy of PVFS insertion under navigation. Given the inherent inaccuracies associated with navigation systems, the authors propose and evaluate a novel stepwise method of inserting PVFSs, called stepwise PVFS with a focus on achieving the correct screw tip location for good cortical bone purchase.

Methods: The authors conducted a retrospective analysis of 12 patients (78 screws) who underwent cervical spine fixation with stepwise PVFS under O-arm navigation between October 2022 and February 2024. The accuracy of screw placement was evaluated using postoperative computed tomography (CT) scans.

Results: A total of 78 PVFSs were inserted in 5 men and 7 women, with an average age of 75 years (range, 52-85 years). The mean follow-up period was 471 days (range, 47-834 days). There were no adverse events related to screw insertion. Postoperative CT scans revealed that 70 screws (90%) were placed in the ideal position. Among the 8 screws that did not achieve the ideal position, 4 had lateral deviation (located in a lateral mass), whereas the other 4 were too short. There were no cases of screw loosening at the final follow-up.

Conclusion: The present study demonstrates that the stepwise PVFS method under navigation guidance achieves higher accuracy in PVFS placement compared with conventional fluoroscopy-guided PVFS, as reported in previous studies.