Abstract
Objective The present study aims to evaluate the screw length and trajectory angles for posterior
atlantoaxial fixation in a Portuguese population, through the study of cervical computed
tomography (CT) scans.
Methods Cervical CT scans of 50 adults were measured according to predefined screw trajectories
of C1-C2 transarticular (C1C2TA), C1 lateral mass (C1LM), C2 pedicle (C2P), C2 pars
and C2 laminar (C2L) screws. For each of these trajectories, screw length and angles
were measured and compared between males and females.
Results For the C1C2TA screw trajectory, the mean length, medial, and cranial angles were
34.12 ± 3.19 mm, 6.24° ± 3.06, and 59.25° ± 5.68, respectively, and for the C1LM screw
trajectory, they were 27.12 ± 2.15 mm, 15.82° ± 5.07, and 13.53° ± 4.80, respectively.
The mean length, medial, and cranial angles for the C2P screw trajectory were 23.44 ± 2.49 mm,
27.40° ± 4.88, and 30.41° ± 7.27, respectively; and for the C2 pars screw trajectory,
they were 16.84 ± 2.08 mm, 20.09° ± 6.83, and 47.53° ± 6,97. The mean length, lateral,
and cranial angles for the C2L screw trajectory were 29.10 ± 2.48 mm, 49.80° ± 4.71,
and 21.56° ± 7.76, respectively. There were no gender differences except for the lengths
of the C1C2TA (p = 0,020) and C2L (p = 0,001) screws, which were greater in males than in females.
Conclusion The present study provides anatomical references for the posterior atlantoaxial fixation
in a Portuguese population. These detailed data are essential to aid spine surgeons
to achieve safe and effective screw placement.
Keywords
atlantoaxial joint - bone screws - cervical vertebrae - joint instability - surgical
fixation devices
