Authors: KEREM ATALAR, ZAFER KUTAY COŞKUN, AHMET MEMDUH KAYMAZ

Abstract: Background/aim: Cervical instability can be caused by a variety of factors, including trauma, tumors, or infection. The cervical transpedicular screw (CPS) is one of the most modern procedures for treating cervical instability. Despite the fact that numerous innovative techniques for CPS have been proposed, the appropriate screw entry points and screw directions have yet to be thoroughly established. The aim of this study is to determine the screw insertion angles and screw entry point distances based on reference points, pedicle axis lengths, and pedicle axis intersections for each vertebra from cervical (C) C2 to C7 in both right and left by gender and age groups. Materials and methods: In this study, computed tomography (CT) images of patients who underwent cervical examination for any reason were evaluated retrospectively. A total of 100 patients (59 men and 41 females), ranging in age from 18 to 79 years (mean 43 years), were randomly selected for the study. Patients with a history of cervical pathology or surgery were excluded. CT images turned into 3D reconstructed images and density settings were made so that bone tissue could be best observed using OsiriX software. Pedicle axis length (PAL), pedicle transverse angle (PTA), pedicle sagittal angle (PSA), distance of screw entry point to lateral notch (DLN), distance of screw entry point to inferior articular process (DIAP), and pedicle axis intersections were measured. Results: According to our findings, the optimal entry point should be 2-4 mm medial to the lateral notch and 8-12 mm superior to inferior articular process. PTA ranges between 30 to 45°, while PSA ranges between 11 to 15°. Except for the C2 pedicles, which were slightly shorter, the pedicle axis lengths (PAL) were similar from C3 to C7 in the total group. The intersection of the right and left pedicle axes was determined to be the most in C4 (51.21% in females and 72.88% in males). Conclusions: This study has shown that intersections of the pedicle axis must be considered in both genders, especially in C4. Standardizing optimal entry points and trajectories is crucial for improving the CPS technique's safety and effectiveness.

Keywords: Optimal screw positioning, cervical vertebrae, cervical transpedicular screw, 3D reconstruction

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