Tomographic Morphometric Analysis of the Subaxial Cervical Pedicles for Minimally Invasive Fixation Techniques

Introduction: Cervical pedicle screw fixation offers significant biomechanical advantages, yet its adoption is constrained by concerns about potential complications, particularly vertebral artery injury. While minimally invasive techniques have been explored, their widespread utilization remains limited.
This study's primary aim was to elucidate the morphological characteristics of cervical pedicles and assess the optimal trajectories and entry points for instrumenting the cervical spine, taking into consideration minimally invasive and transmuscular techniques.

Methods: Cervical CT scans were performed on consecutive patients using a Philips Ingenuity 128-slice scanner (Ingenuity Core 128, Philips Healthcare). A total of 91 patient scans were analyzed, encompassing measurements of pedicle width, height, screw length, transverse angle, and trajectory parameters.

Results: The pedicle width, pedicle height, and screw length progressively increased from C3 to C7. Males had significantly larger pedicles and longer screw lengths than women (p < 0.05). The pedicle transverse angle was widest at C4 (54.2 ± 3.5) and narrowest at C7 (43.5 ± 4.7), with a statistically significant difference between levels (p < 0.001). The ideal starting point for a percutaneous approach ranged from 68.2 ± 9.6 mm at C7 to 74.5 ±13.7 mm at C4. A strong positive correlation was found between higher BMI and larger distances (r: 0.67). The canal-vertebral angle showed a progressive decrease from C3 to C7, ranging from 56.2 ± 7.6 to 50.8 ± 10.5. The pedicle facet angle and the distance from the inferior tip of the inferior articular process to the ideal starting point increased progressively from C3 to C7, with a statistically significant difference between levels (p < 0.05).

Conclusion : This study provides comprehensive insights into the morphological characteristics of cervical pedicles and optimal trajectories for safe screw instrumentation. The findings are in harmony with existing literature, offering valuable guidance for the safer and more accurate placement of cervical pedicle screws.