Three-dimensional morphometry and clinical implications of the atlantoaxial lateral mass joint: a study of sexual...

The atlantoaxial lateral mass joint is a pivotal structure facilitating cervical rotation and flexion-extension. Its morphological characteristics are intrinsically linked to degenerative pathologies and segmental instability. However, comprehensive three-dimensional anatomical data, particularly regarding sex-specific variations, remain insufficient. This study aimed to perform precise three-dimensional measurements of the atlantoaxial lateral mass joint in normal adults to elucidate its normative morphological features and sexual dimorphism, which may serve as a morphological reference for future studies exploring surgical planning, personalized implant design, and biomechanical modeling.

A retrospective analysis was conducted on 200 patients (100 males, 100 females; aged 18-50 years) without cervical abnormalities, using cervical three-dimensional spiral CT images obtained between December 2024 and December 2025. Parameters measured on reconstructed images included the anteroposterior diameter (sagittal plane), left-right diameter (coronal plane), medial inclination angle, joint space width, and distance from the transverse foramen to the lateral mass joint midpoint. Statistical analysis employed independent samples t-tests to evaluate sex differences.

All parameters exhibited significant sex differences (P < 0.05). Males consistently demonstrated significantly larger anatomical dimensions than females across all linear and angular metrics. Notably, these sex-related differences remained significant after adjusting for Body Mass Index (BMI) via ANCOVA (P < 0.05), indicating that the observed dimorphism reflects intrinsic biological traits rather than overall body habitus.

This study systematically quantifies the three-dimensional anatomy of the atlantoaxial lateral mass joint and confirms significant sexual dimorphism.These findings offer morphological context that may be relevant when investigating atlantoaxial pathologies and provide anatomical baseline data for future research concerning personalized fusion device design, surgical navigation, and finite element simulations.