Morphometric parameters of the odontoid process of C2 vertebrae, in Indian population, a CT evaluation

BACKGROUND: Osteosynthesis of odontoid fractures, especially for type II odontoid fractures, is often achieved by the placement of screws. Here, utilizing CT, we evaluated the normal anatomy of the odontoid process in an Indian population to determine whether one or two screws could be anatomically accommodated to achieve fixation. METHODS: CT-based morphometric parameters of the odontoid process were assessed in 200 normal Indian patients (2018–2020). RESULTS: Of 200 patients, 127 were male, and 73 were female. The mean minimum external transverse diameter (METD) was 8.80 mm (range 6.1–11.9 mm). Six (3%) patients had a minimum internal transverse diameter (TD) of >8.0 mm that would allow for the insertion of two 3.5-mm cortical screws without tapping, while 10 (5%) patients had TDs of <7.4 mm; none had diameters of <5.5 mm. The mean length of the implant was 36.45 mm in females and 36.89 mm in males, and the mean angle of screw insertion was 60.34° in females and 60.53° in males. CONCLUSION: About two-thirds (59%) of the 200 subjects in our study had a METD of <9 mm, indicating the impracticality for introducing second screws for odontoid fixation.