Sagittal spino-pelvic alignment in adults: The Wakayama Spine Study

Objectives To establish the normal values of spino-pelvic alignment and to clarify the effect of age-related changes using large, community-based cohorts. Methods In this study, data from 1461 participants (466 men, 995 women) were analyzed. On lateral standing radiographs, the following parameters were measured: thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), and C7 sagittal vertical axis (SVA). All values are expressed as the mean +/- standard deviation. The Spearman rank correlation coefficient was used to examine correlations between variables of spino-pelvic parameters. Finally, we analyzed the relationship between age and spino-pelvic parameters. Therefore, we entered values for the body mass index (BMI), SVA, TK, and PI-LL into a multiple regression model to adjust for potential confounding factors. Results The SVA, TK, and PT increased with age, and LL decreased with age. Regarding sex differences, the TK was statistically significantly larger in men than in women, and LL, PT, and PI were statistically significantly smaller in men than in women. Correlation coefficients between the SVA and TK, between the SVA and PI-LL, and between TK and PI-LL were none, strong, and weak, respectively. Results of multiple regression analysis between age and spino-pelvic parameters showed that the standardized partial regression coefficients for the SVA, TK, and PI-LL were 0.17, 0.30, and 0.23, respectively, in men and 0.29, 0.32, and 0.23, respectively, in women. Conclusions We found that all parameters were significantly associated with age in men and women. The SVA, TK, and PT increased with age, and LL decreased with age. Results of multiple regression analysis also demonstrated that the SVA, TK, and PI-LL are related to age. Indeed, the PI-LL value increased with age. In this study, a more excessive PI-LL mismatch was shown, indicating an increased risk of spinal malalignment. Differences in the absolute values of spino-pelvic parameters in each sex were small yet statistically significant. Thus, further study should be performed to corroborate this finding.