Quantitative Analysis of Subaxial Cervical Pedicle Diameters: A CT Scan-Based Study of 50 Patients

Introduction: Subaxial cervical pedicle screws (C3-C7) are increasingly employed in complex cervical spine reconstructions, offering greater fixation strength than traditional methods. However, anatomical variability and the risk of screw malpositioning raise concerns about safety and efficacy. Initially described in 1994, cervical pedicle screw fixation demonstrated high stability and strength in treating traumatic cervical spine injuries.
Advancements in imaging modalities, particularly CT scans, have revolutionized pre-operative planning, allowing for precise measurements of pedicle dimensions and tailored screw selection. This study aimed to quantify subaxial cervical pedicle diameters in a large cohort using CT scans, providing valuable anatomical data for surgical planning and screw selection.

Methods: This study analyzed 50 consecutive CT scans of the cervical spine from patients without previous cervical surgery. All scans were acquired using a standardized protocol with 1 mm slice thickness. The diameters of the subaxial cervical spine pedicles were measured (250 vertebrae or 500 pedicles). Measurements were performed using the measurement tools of the CT imaging software. Pedicle diameters were measured based on the most outer cortex of the pedicle, taken perpendicular to the axis of the pedicle, and measured in millimeters up to 0.1 mm.

Results: Significant variations in pedicle diameters were found. In males, the mean transverse diameters ranged from 5.1 mm (C3) to 6.6 mm (C7), while in females, they ranged from 4.5 mm (C3) to 6.0 mm (C7). Using a 4 mm cutoff for a 3.5 mm screw, between 0% and 13.4% of male pedicles and 0% to 21.1% of female pedicles were deemed unsuitable for pedicle screw fixation.

Conclusion : This study underscores the importance of meticulous pre-operative planning and screw selection for subaxial cervical pedicle screw fixation. The data highlights the anatomical variations within this region, emphasizing the need for precise screw placement to avoid complications. These findings can inform surgical decision-making, leading to safer and more effective cervical spine surgeries. Further research examining additional factors influencing pedicle dimensions (such as age, ethnicity, bone density, and degenerative changes) is necessary to enhance our understanding and improve patient outcomes.