The cohort study for the determination of reference values for spinopelvic parameters (T1 pelvic angle and global tilt) in elderly volunteers

T1 pelvic angle (TPA) and global tilt (GT) are spinopelvic parameters that account for trunk anteversion and pelvic retroversion. To investigate spinopelvic parameters, especially TPA and GT, in Japanese adults and determine norms for each parameter related to health-related quality of life (HRQOL). Six hundred and fifty-six volunteers (262 men and 394 women) aged 50-92 years (mean, 72.8 years) were enrolled in this study. The incidence of vertebral fracture, spondylolisthesis and coronal malalignment were measured. Five spinopelvic parameters (TPA, GT, sagittal vertical axis [SVA], pelvic tilt [PT], and pelvic incidence-lumbar lordosis [PI-LL]) were measured using whole spine standing radiographs. The mean values for each parameter were estimated by sex and decade of life. HRQOL measures, including the Oswestry Disability Index (ODI) and EuroQuol-5D (EQ-5D), were also obtained. Pearson's correlation coefficients were determined between each parameter and HRQOL measure. Moreover, the factors contributing to the QOL score were calculated using logistic regression with age, sex, the existence of vertebral fracture and spondylolisthesis, coronal malalignment (coronal curve > 30A degrees) and sagittal malalignment (SVA > 95 mm) as explanatory variables and the presence of disability (ODI > 40) as a free variable. The mean values for the spinopelvic parameters were as follows: TPA, 17.9A degrees; GT, 23.2A degrees; SVA, 50.2 mm; PT, 18.6A degrees; and PI-LL, 7.5A degrees. TPA and GT strongly correlated with each other (r = 0.990) and with the other spinopelvic parameters. TPA and GT correlated with ODI (r = 0.339, r = 0.348, respectively) and EQ-5D (r = -0.285, r = -0.288, respectively), similar to those for SVA. TPA, GT, PT, and PI-LL were significantly higher in women than in men. PT and PI-LL gradually increased with age, while TPA, GT, and SVA tended to deteriorate after the 7th decade. Based on a logistic regression analysis, the deterioration of ODI was mostly affected by the sagittal malalignment. The TPA and GT cut-off values for severe disability (ODI > 40) based on linear regression modeling were 26.0A degrees and 33.7A degrees, respectively. We determined reference values for spinopelvic parameters in elderly volunteers. Similar to SVA, TPA and GT correlated with HRQOL. TPA, GT, PT, and PI-LL were worse in women and progressed with age.