Superior Articular Facet Angulation of the Axis Vertebra in a South African Population Sample using an Osteological Analysis

The superior articular facets (SAFs) of the axis vertebra (C2) are critical to atlantoaxial stability and cervical spine biomechanics. Variation in SAF angulation may influence joint congruency, load distribution, and surgical corridor orientation, with direct implications for imaging interpretation and operative planning. Population-specific morphometric data from South African osteological samples remain limited, constraining translational application. A cross-sectional osteological study was conducted on 200 adult axis vertebrae from the Raymond A. Dart Collection, South Africa. Bilateral SAF angulation was quantified using standardised digital image analysis. Specimens were stratified by age group, biological sex, and population affinity. Statistical analyses assessed bilateral asymmetry and between-group differences, with significance (p < 0.05). Mean SAF angulation measured 26.13° on the right and 25.98° on the left, demonstrating minimal bilateral asymmetry (p = 0.679). No significant differences were observed across age groups (right: p = 0.675; left: p = 0.239) or biological sex (right: p = 0.400; left: p = 0.154). An overall association with population affinity was identified (p = 0.027; p = 0.008); however, side-specific comparisons were not significant (right: p = 0.468; left: p = 0.298). Variability within subgroups was low. SAF angulation demonstrates relative morphological consistency across demographic subgroups in this South African sample. Although population affinity showed an overall association, this was not consistently observed in side-specific analyses. These findings provide clinically relevant, population-specific reference values that may support preoperative planning, implant trajectory considerations, and radiological assessment. Further work integrating 3D imaging and biomechanical modelling is required to strengthen translational applicability. • Superior articular facet of axis forms the plateau of atlanto-axial articulation. • SAF angulation is an important indicator of cervical vertebral functionality. • No significant differences in SAF angulation observed in SA population groups