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Computed tomography comparison study of two Axis-based C1 transpedicular screw trajectory designs
Hongwei He1, Baiwen Hu2, Pengchao Cai3
1Department of Radiology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China; Medical Imaging Department, Ningbo First Hospital, Ningbo, China.
Background Context:
To our knowledge, there is no comparison study of two different Axis-based C1 transpedicular screw trajectory (TST) designs.
Purpose:
To compare two different Axis-based C1 TST designs.
Study Design:
The computed tomography (CT) morphologic analysis of the two different C1 Axis-based TST designs.
Methods:
Firstly, the design of Axis C/M and related measurements were made on a work station by using neck computed tomography angiography (CTA) data of 62 patients. The central axes (Axis M and Axis C) of C1 TST were designed by multiplanar reconstruction (MPR) technique. Based on Axis M and Axis C, the following parameters were measured: (A, A'), distance between the insertion point (IP) and the midline. (B, B'), distance between IP and the inferior aspect of C1 posterior arch. (C, C'), distance between IP and the C1 anterior cortex of the lateral mass along Axis M/C. (D, D'), insertion angle (IA) based on Axis M/C. (E, E'), the narrowest width of the inner medullary cavity (IMC) along Axis M/C.
Result:
The C1 TST can be designed by MPR technique based on CT volume scan. The design of Axis C trajectory was easier to Axis M trajectory. A, A' were 20.7±1.6mm and 20.6±1.9mm. Both B, B' were 2.0±0.6mm. C, C' were 27.2±2.1mm and 27.5±2.1mm. D, D' were 9.9±5.0°and 10.4±7.7°. E, E' were 5.0±1.3mm and 5.4±1.4mm. Among 62 patients (124 sides), Axis C can be achieved by medial inclination, perpendicular, lateral inclination method in 81.5%, 13.7%, 4.8% sides, respectively; Axis M can be achieved by medial inclination, perpendicular, lateral inclination method in 90.3%, 8.9%, 0.8% sides, respectively.
Conclusion:
Axis C can be a reliable trajectory for C1 transpedicular screw insertion as long as there is no displaced fracture in the C1 pedicle and lateral mass. Because of the individual differences, the ideal C1 TST can be achieved by medial inclination, perpendicular or even lateral inclination method, although its inclination direction is medial in the majority of patients.
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