Accuracy of Cervical Pedicle Screw Placement Using a Patient-Specific Template Guide System in Revision Cervical...

Revision cervical spine surgery is associated with specific technical challenges associated with cervical pedicle screw (CPS) placement because of altered posterior bony anatomy, scar tissue, and limited anatomical landmarks. Although patient-specific template guide systems (TGS) have shown a high level of accuracy in primary CPS placement, there is limited evidence on their application in revision cases. This study aimed to evaluate the accuracy of placement of CPS by using TGS in revision cervical spine surgery and to analyse cervical morphometric parameters across different vertebral levels to better contextualise the feasibility of screw placement and their safety. Given the limited sample size, morphometric comparisons across vertebral levels were considered exploratory and hypothesis-generating.

This was a retrospective analysis using CT of 15 patients who underwent posterior cervical instrumentation with a patient-specific TGS after previous posterior decompression surgery. A total of 90 CPS inserted from C2 until C7 were evaluated. Screw placement accuracy was determined on postoperative CT and graded based on known criteria of deviation. Radiographic parameters of the cervical pedicle and the trajectory of the screws, such as pedicle width, pedicle transverse angle, pedicle medial offset, screw diameter, screw length, pedicle screw transverse angle, and pedicle screw medial offset, were measured. Post-hoc comparisons (Dunn-Bonferroni) were performed with the Kruskal-Wallis test to analyse the inter-level differences.

The study demonstrated a high rate of optimal screw placement, with 95.6% of screws classified as Grade 0 (completely contained within the pedicle), and 4.4% showing minor (<2 mm) cortical breach (Grade 1). There were no Grade 2 or Grade 3 deviations, and there were no neurovascular problems. Pedicle width was significantly different between cervical levels (chi 2 = 19.08, p = .002), with a significantly greater pedicle width at C2 than at C3, C4, and C6 (post hoc). Significant inter-level differences were also detected for all other radiographic and screw parameters (all p < .001), with upper cervical levels showing a distinct morphometric appearance.

CPS placement with patient-specific TGS in revision cervical spine surgery was found to have high accuracy and clinical safety. Significant anatomical variation across cervical levels at C2 emphasizes the significance of detailed preoperative planning. These findings support the feasibility of TGS-assisted CPS placement in revision settings.