Three-Dimensional Surface Topography for the Assessment of Spinal Alignment: A Cross-Sectional Study of Biomechanical Correlates

Background/Objectives: Spinal alignment is a key determinant of biomechanical function and postural stability, particularly during periods of growth and development. Three-dimensional (3D) surface topography offers a non-invasive method for assessing spinal posture. This study aimed to evaluate spinal alignment parameters in a mixed adolescent and adult population, to investigate sex-related differences, and to analyze biomechanical relationships between spinal components. Methods: A total of 98 participants (aged 11–45 years) underwent 3D spinal surface topography assessment. Descriptive statistics were calculated for sagittal, coronal, and rotational parameters. Group comparisons between sexes were performed using independent samples t-tests. Pearson correlation analysis and linear regression were used to assess the relationships between spinal parameters. Logistic regression analysis was conducted to identify predictors of clinically relevant rotational asymmetry (surface rotation RMS > 6°). Results: Most participants exhibited near-physiological sagittal alignment, with thoracic kyphosis and lumbar lordosis within normal ranges. However, approximately 20% demonstrated clinically relevant rotational asymmetry. Female participants showed significantly higher rotational asymmetry compared to males (p = 0.008), while sagittal parameters did not differ significantly. Strong correlations were observed between thoracic kyphosis and cervical sagittal displacement (r = 0.77). Rotational asymmetry was negatively correlated with sagittal parameters and significantly predicted coronal imbalance (β = 0.38, p < 0.01; R2 = 0.21). Conclusions: 3D surface topography provides a non-invasive method for assessing external postural alignment and surface-based asymmetries. Rotational asymmetry appears to represent a relevant component of spinal imbalance and is associated with coronal deviation within a multi-planar framework. These findings support the use of integrated biomechanical assessment in the evaluation of spinal alignment.