Abstract
STUDY DESIGN: Monocentric, retrospective, cross-sectional study. OBJECTIVE: To investigate the age-related normative values of sagittal parameters and establish their relationships in asymptomatic community-dwelling adults aged over 50. BACKGROUND CONTEXT: Degenerative changes in the spine with aging alter the sagittal balance, causing spine pathologies. However, there was a lack of comprehensive study on age-related normative values of sagittal alignment and their relationship during degenerative evolution. METHODS: Among a total of 1,370 volunteers, 701 asymptomatic volunteers were recruited. Participants underwent a lateral X-ray, and sagittal parameters were assessed using a customized computer application. RESULTS: Age showed a stronger correlation with upper arc of thoracic kyphosis (Upper_TK) (r=0.39) compared to sagittal vertical axis (SVA) (r=0.28) and T1_slope (r=0.29). Lumbar lordosis (LL) did not exhibit a significant decrease with age. The geometrical relationship revealed a significant correlation between TK and LL (r=0.52), and LL and pelvic incidence (PI) (r=0.63), as per the equations: TK=Upper_TK+Lower arc of TK (Lower_TK), LL=Upper arc of LL (Upper_arc)+sacral slope (SS), Lower_TK≈Upper_arc, and PI=SS+pelvic tilt (PT). However, after removing intermediate control variables of Lower_TK (Upper_arc) and SS, the correlation between TK, LL, and PI was statistically weak, due to the little to no correlation between Lower_TK (Upper_arc), SS, and PT. Upper_arc (Lower_TK) was a relatively stable parameter with an age-independent value of 15.93±5.61° in elderly adults. For adults aged 60, Upper_TK significantly increased with age, while individuals over 75 exhibited a significant increase in PT and a decrease in SS and LL. CONCLUSIONS: Our study provided a normative age-related value of spinal sagittal parameters. To assess the spinal sagittal alignment, it was suggested that LL and TK be divided into two tangential arches based on the location of the lordotic or kyphotic apex. This study offered insights for spine surgeons in preparing for surgical corrections.