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

Abstract

ObjectiveTo 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. MethodsThe 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. ResultsThe 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). ConclusionsSoutheast 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.