We analyzed the anatomy of C3–C6 cervical pedicles with reconstructed computed tomography images.
The objective of the study was to estimate the feasibility and to understand the surgical anatomy in order to reduce pedicle penetration.
Summary of Background Data:
It is necessary to minimize pedicle penetration by anatomic analysis of cervical pedicles. Many studies have been conducted on cervical pedicle anatomy and cervical pedicle screw fixation, yet there are debates about the feasibility and surgical anatomy.
Oblique axial and oblique sagittal images were reconstructed from a 1 mm cut computed tomography image. The pedicle transverse diameter, pedicle length, pedicle convergence angle (CA), and pedicle distance were measured on the oblique axial images. The pedicle sagittal diameter, pedicle sagittal angle (SA), and lateral mass index were measured on the oblique sagittal images. The multiple t test was used for statistical analysis.
The averages of the pedicle transverse diameter ranged from 5.79 to 6.19 mm, the pedicle length ranged from 16.24 to 17.56 mm, the CA ranged from 47.49 to 48.86 degrees, the pedicle distance ranged from 22.67 to 24.93 mm, the SA ranged from −15.43 to 19.98 degrees, and the lateral mass index ranged from 0.64 to 1.25.
Because of a tight safe margin, to reduce pedicle penetration the screw should be inserted along the pedicle. With regard to SA, C3 and C4 have a risk of upper end plate penetration. However, C5 and C6 have a risk of facet joint violation, which needs C4 and C5 inferior articular process removal for screw placement. The entry point at C3 and C4 is near one third of the lateral mass height from the posterior border of the superior articular process at the posterolateral border of the lateral mass. The entry point at C5 is near the posterolateral border of the superior articular process and that at C6 is superior to the posterior border of the superior articular process at a line medial to the posterolateral border of the C5 lateral mass. During insertion, not only CA but even SA should be considered carefully to reduce pedicle penetration.