A computed tomographic morphometric analysis of the odontoid process for using anterior double Herbert screws fixation in the Southeast Asian population

Abstract

Objective: To conduct a radiographic CT scan study of the axis (C2 vertebra) of the cervical spine in the Southeast Asian population was analyzed to evaluate the feasibility of fitting two 3.0-mm anterior odontoid screws. The odontoid process and the C2 vertebra have been morphometrically analyzed in several different populations, but not in the people of Southeast Asian. Methods: The bicortical diameter of the isthmus of the odontoid process as well as its thickness were measured using 200 CT cervical images. The length of the 3.0-mm anterior screws in the mid sagittal and coronal views of C2 were measured. All parameters were measured to a precision of 0.1 mm. with statistical analysis. Results: The 200 CT-scans included 100 males (50%) and 100 females (50%). The mean radiographic anterior odontoid screw length in mid sagittal view was 37.41 ± 2.27 mm. (38.26 ± 2.45 vs 35.44 ± 2.38 for males and females, respectively), the right screw length in coronal view was 33.95 ± 2.84 mm. (34.72 ± 2.59 vs 32.16 ± 2.59), the left screw length in coronal view was 33.87 ± 2.86 mm. (34.65 ± 2.59 vs 32.03 ± 2.62) and the mid screw length in coronal view was 33.61 ± 2.83 mm. (34.37 ± 2.59 vs 31.84 ± 2.57). The mean diameter of the bicortical isthmus of the of odontoid was 8.16 ± 1.09 mm. (8.42 ± 1.07 vs 7.55 ± 0.86), the mean inner anteroposterior (AP) diameter was 11.28 ± 1.06 mm. (11.58 ± 0.99 vs 10.57 ± 0.84), the mean outer AP diameter was 6.83 ± 1.07 mm. (6.93 ± 1.12 vs 6.60 ± 0.92), and the mean inner transverse diameter was 10.16 ± 1.11 mm. (10.29 ± 1.14 vs 9.88 ± 1.00). Males had a significantly greater mean anterior odontoid screw length and bicortical diameter of the isthmus of odontoid than females (p < 0.001). Conclusions: Southeast Asian population, a 3.0-mm double anterior odontoid screw configuration can be inserted into the odontoid. However, prior to the procedure, a CT scan should be accomplished to assess screw acceptance and to determine appropriate screw sizes.