CT evaluation of cervical pedicle in a Chinese population for surgical application of transpedicular screw placement

Abstract

The lower cervical pedicle size differs between the Chinese and the non-Chinese population. Knowledge of pedicle dimensions and surface landmarks is crucial for the safe placement of screws, but few quantitative data concerning the lower cervical pedicle using CT scan and multiplanar reformations (MPR) in a Chinese population exist. The aim of this study was to evaluate lower cervical pedicle (C3-C7) dimensions in a Chinese population by computed axial tomography for surgical application. The dimensions of the pedicles (C3-C7) were determined in 60 patients from CT images of cervical spinal lesions. Measurements of pedicle height, width, pedicle axis length, effective length, and two angles of the pedicles, the distances from the projection point of the pedicle axis to the lateral edge of the lateral mass and to the inferior edge of the superior facet were measured. The smallest outer pedicle width was found at C3 among the female and C4 among the male. This measurement was significantly different between male and female patients in the outer pedicle width (P < 0.05; independent samples t test) at C3 and C4. The mean values of the outer pedicle width ranged from 5.4 to 6.7 mm in males, and 4.4 to 6.3 mm in females. The projection point of the pedicle axis in the lateral-superior area of the cervical lateral mass was the most important. There were significant correlations (P < 0.01; Kendall's W test) between the vertebral level and both pedicle angles (PTA and PSA). The smallest pedicle transverse angle was at C7 in males and females. The cervical spinal cord or vertebral artery may be at risk of injury if the angulation of the screw insert is over-medial or over-lateral in the transverse plane. Therefore, preoperative CT evaluation of pedicle transverse angle is very important. Considering the amount of variation among individuals, our data on CT measurements of pedicle in a Chinese population in conjunction with evaluation of the results of preoperative CT may enhance the safety of transpedicular screw fixation in the lower cervical spine.