Avaliação tomográfica de parâmetros morfométricos do processo odontoide relacionados à fixação interna com parafusos

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.

Feasibility of anterior screw fixation in children: a tomographic study

PURPOSE

Morphology measures of the odontoid process in children under 12 years old were carried out to demonstrate the viability of anterior internal fixation in this population once their active profile may not be compatible with successful conservative treatment.

METHODS

During a 6-month period, 36 tomographic examinations of the cervical spine region that provided visualization of the odontoid process were selected. Group 1 included children between 6 and 9 years of age, and group 2 contained children from 9 to 12 years of age. There were 23 (63.8%) male patients and 13 (36.2%) female patients. Patients diagnosed with a tumor, an infection, fracture non-union, or congenital malformation were excluded. Exams were ordered as part of a protocol applied to non-specific neck pain and pediatric trauma entries. The following parameters were analyzed: (1) screw attack angle, (2) height of the odontoid process, and (3) minimal transverse diameter of the odontoid process.

RESULTS

In Groups 1 and 2, the average values of the screw attack angle were 55.9° ± 2.3° and 54.8° ± 4.5°, respectively; the average heights of the odontoid process were 26.58 ± 3.28 and 29.48 ± 3 mm, respectively, and the average minimal transverse diameter of the odontoid process were 6.57 ± 1.08 and 6.23 ± 0.88 mm, respectively. The minimal transverse diameter of the odontoid process was statistically higher in males than that in females, regardless of age (p = 0.007).

CONCLUSION

In both groups, the minimal transverse diameter of the odontoid process allowed for the use of one 3.5-4.5 mm screw for anterior internal fixation. These slides can be retrieved under Electronic Supplementary Material.