Side-specific and sex-related computed tomography morphometric variations of the atlas (C1) and axis (C2) in Vietnamese adults: Implications for safe posterior atlantoaxial fixation
DOI:
https://doi.org/10.25305/unj.352621Keywords:
atlas vertebra, axis vertebra, cervical vertebrae, tomography, computed tomography, morphometry, atlantoaxial joint, spineAbstract
Objective: To provide a comprehensive computed tomography (CT) morphometric analysis of the atlas (C1) and axis (C2) in Vietnamese adults, evaluate sex-related and side-specific differences, and determine the implications for posterior atlantoaxial screw fixation.
Materials and methods: A retrospective cross-sectional CT study was conducted on 150 adults (112 men and 38 women; mean age 51.9 ± 15.1 years). Multiplanar reconstruction was used to measure C1 lateral mass length (C1-LML), C1 lateral mass width (C1-LMW), maximal medial (C1-MTA), lateral (C1-LTA), cranial (C1-CTA), and caudal (C1-CdTA) trajectory angles bilaterally. C2 parameters included isthmus height (C2-IH), canal height (C2-CH), and pedicle width (C2-PW).
Results: Significant sex-related differences were observed, with men demonstrating greater right C1-LML and C1-LMW values (p = 0.029 and p = 0.005, respectively) as well as larger right C1-LTA, C1-CTA, and C1-CdTA (all p < 0.05). Left C2-PW was also significantly greater in men (p = 0.020). In addition, side-specific asymmetry was identified: C1-LTA, C1-CTA, and C1-CdTA differed significantly between sides (p = 0.009–0.021), and C2-CH was greater on the left (p < 0.001). Age showed weak negative correlations with selected C2 parameters.
Conclusions: Upper cervical morphology demonstrates measurable asymmetry and sex-related variation. Preoperative planning for C1–C2 instrumentation should therefore be individualized and side-specific.
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