An Intraoperative Trajectory-Determined Strategy of Patient-Specific Drill Template for C₂ Transoral Pedicle Insertion in Incomplete Reduction of Atlantoaxial Dislocation: An In Vitro Study

Objectives: This study aims to explore a novel intraoperative trajectory-determined strategy of grouped patient-specific drill templates (PDTs) for transoral C₂ pedicle screw insertion (C₂ TOPI) for atlantoaxial dislocation (AAD) with incomplete reduction and to evaluate its efficiency and accuracy.

Methods: Ten cadaveric C₂ specimens were scanned by computed tomography (CT) and randomly divided into two groups (the PDT and freehand groups). A novel intraoperative trajectory-determined strategy of grouped PDTs was created for AAD with incomplete reduction. C₂ TOPI was performed by use of the PDT technique and the fluoroscopy-guided freehand technique. After surgery, the screw deviations from the centroid of the cross-section at the midpoint of the pedicle and screw position grades were assessed in both groups.

Results: Compared to the freehand group, the PDT group had a significantly shorter surgery time than the freehand group (47.7 vs 61.9 min, P < 0.001). The absolute deviations from the centroids between the preoperative designs and postoperative measurements on the axial plane of the pedicle were 1.19 ± 0.25 mm in the PDT group and 1.82 ± 0.51 mm in the freehand group. On the sagittal plane of the pedicle, the corresponding values were 1.10 ± 0.33 mm in the PDT group and 1.70 ± 0.49 mm in the freehand group. The absolute deviations of the free-hand group on both the axial and sagittal planes were higher than that of the freehand group (P < 0.05 and P < 0.05, respectively). For the grade of screw insertion position, nine (90%) were observed in type I and one (10%) in type II in the PDT group, whereas five (50%) were in type I, three (30%) were in type II, and two (20%) in type III in the freehand group. Statistical differences could not be found between the groups in terms of the screw positions (P > 0.05).

Conclusion: The novel intraoperative trajectory-determined strategy of grouped PDTs can be used as an accurate and feasible method for C₂ TOPI for AAD with incomplete reduction.