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Study design: National cross-sectional study. Objective: Thoracic kyphosis (TK) is related to sagittal parameters as pelvic tilt (PT), lumbar lordosis (LL) and pelvic incidence (PI). The equation TK = 2 (PT+LL–PI) was validated for adolescents. The purpose of this study was to investigate if this equation correctly predicts TK regardless of age. Methods: Sagittal alignment parameters were assessed on full spine radiographs of 2599 individuals without spine pathology (1488 females, 1111 males). Calculated TK (CTK) = 2 (PT+LL–PI) and measured TK (MTK) were compared by calculating the gap and using a linear regression between both parameters. Subgroup analyses were performed for gender, age, TK groups (≤20°, 21°-40°, 41°-60°, >60°), and PI groups (<45°, 45°-60°, >60°). Results: Average values in the total population were: MTK 45.0°, CTK 36.9°. Average TK gap was 8.1°, 5.2° in females (intercept 11.7, slope.61) and 11.9° in males (intercept 7.1, slope.58). The mean gap was 3.6° for 15-34 years, 5.7° under 15 years and it increased progressively after 35 years with a maximum of 19.9° over 80 years. The gap also increased with the amount of MTK: -3.5° for TK<20° up to 17.3° for TK >60°. Differences in gaps were minor between PI groups. The intercept was smallest and slopes >.6 for PI <45° and TK ≤20°. Conclusion: The formula TK=2 (PT+LL-PI) yielded moderate accuracy for adolescents and young adults, but did not fit for over 35 years and under 15. The amount and variance in TK increased in elderly subjects, which made the formula less accurate. [ABSTRACT FROM AUTHOR]

Study design: Descriptive radiographic analysis of a prospective multi-center database. Objective: This study aims to provide normative values of spinopelvic parameters and their correlations according to age and pelvic incidence (PI) of subjects without spinal deformity. Methods: After Institutional Review Board (IRB) approval, 1540 full spine radiographs were analyzed. Subjects were divided into 3 groups of PI: low PI < 45°, intermediate PI 45–60°, high PI > 60°, and then stratified by age (20–34, 35–49, 50–64, > 65 Y.O). Pelvic and spinal parameters were measured. Statistical analysis between parameters was performed using Bayesian inference and correlation. Results: Mean age was 53.5 years (845 females, 695 males, range 20–93 years). In low PI group, lumbar lordosis (LL) decrease was mainly observed in the 2 younger age groups. In medium and high PI groups, loss of lordosis was linear during aging and occurred mainly on the distal arch of lordosis. Moderate PI group had a stable lordosis apex and thoracolumbar inflection point. High PI group had a stable thoracolumbar inflection point and a more distal lordosis apex in elderly subjects. For all subjects, kyphosis and pelvic tilt (PT) increased with age. There was a constant chain of correlation between PI and age groups. Proximal lumbar lordosis (PLL) was correlated with kyphosis and sagittal vertical axis (SVA C7), while the distal lumbar lordosis (DLL) was correlated with PI and PT. Conclusion: This study provides a detailed repository of sagittal spinopelvic parameters normative values with detailed analysis of segmental kyphosis and lordosis distribution according to gender, age, and PI. [ABSTRACT FROM AUTHOR]