Association between thoracic hyperkyphosis and sagittal skeletal malocclusion patterns: a cross-sectional study

Interactions between spinal posture and craniofacial morphology have been suggested, yet the biomechanical relationship between thoracic sagittal alignment and skeletal malocclusion remains insufficiently quantified. This observational cross-sectional study investigated the association between thoracic hyperkyphosis and skeletal malocclusion patterns and evaluated whether thoracic curvature is statistically associated with sagittal craniofacial relationships. Lateral cephalometric and spinal radiographic measurements were obtained from 166 individuals. Thoracic kyphosis angles and craniofacial skeletal parameters determining by Python (version 3.13) were analyzed using multinomial regression models adjusted for demographic variables. Thoracic hyperkyphosis was significantly associated with sagittal skeletal discrepancies ( p < 0.05). In addition to the ANB-based analysis, individual assessments of SNA and SNB were performed to evaluate maxillary and mandibular contributions. No statistically significant differences were found in SNA ( p = 0.245), whereas SNB showed a small but significant difference ( p = 0.033) between hyperkyphotic and control groups. Path-based correlation decomposition showed that Cobb angle statistically accounted for approximately 33% of the age-ANB bivariate correlation (path coefficient β = 0.08, 95% bootstrap CI: 0.03–0.15). This is a descriptive decomposition of cross-sectional correlations and does not imply causation or temporal precedence. Receiver operating characteristic (ROC) analysis showed moderate discriminatory performance for identifying skeletal malocclusion groups (area under the curve [AUC] = 0.74). These findings demonstrate a cross-sectional statistical association between thoracic spinal alignment and craniofacial skeletal patterns. Due to the observational nature of the study design, causal relationships cannot be inferred. Postural assessment may be considered as a complementary component in orthodontic evaluations, but this recommendation requires confirmation in prospective longitudinal studies.