The Longitudinal Changes of Cervical Sagittal Alignment in a Non-surgical Cohort: A 12-Year Longitudinal Study

Study Design A retrospective longitudinal observational cohort study. Objective This study aimed to quantitatively evaluate the natural progression of cervical sagittal alignment parameters in non-surgical patients over a mean 12-year follow-up period, with a specific focus on age- and sex-related variations. Methods Radiographic data were analyzed from 198 non-surgical patients (mean age: 50.6 years) over a mean follow-up duration of 142 months (range: 96–203 months). Key parameters measured included C2-7 Cobb angle, range of motion (ROM), cervical sagittal vertical axis (SVA), T1 slope, C7 slope, thoracic inlet angle (TIA), and neck tilt. Longitudinal changes were evaluated alongside the influences of age and sex. Results The cohort exhibited significant, age-accelerated progression in cervical sagittal alignment. Overall cervical ROM decreased markedly from 50.10° to 41.14° (P<0.001). Concurrently, a progressive trend toward anterior sagittal imbalance was observed, characterized by significant increases in C7 slope, T1 slope (24.86° to 26.41°), TIA, and SVA (22.38 mm to 24.59 mm). In contrast, the C2-7 Cobb angle and neck tilt remained stable. Advanced age was a strong independent predictor of deterioration. Furthermore, males experienced significantly greater reductions in ROM and more pronounced increases in SVA compared to females. Conclusion The natural aging process of the cervical spine is characterized by progressive stiffening and a trajectory toward anterior sagittal malalignment, primarily mediated through a compensatory increase in T1 slope that is not matched by a reciprocal increase in lordosis. These data highlight the need to account for natural physiological drift when evaluating ultra-long-term iatrogenic surgical effects.