Normal values for sagittal spinal alignment: a study of Brazilian subjects.

Objectives: The purpose of this study is to investigate the normal values of and chain of correlations between spinopelvic parameters in a Brazilian population.

Methods: This is a prospective observational study including asymptomatic adult subjects who had full spinal radiographs performed. The subjects were stratified by age into 3 groups (18-39 years old, 40-59 years old, and >60 years old), and radiographic parameters were compared across age groups and gender using ANOVA and Student's t-test, respectively. The relationships between various radiographic parameters were evaluated with Pearson correlation coefficients.

Results: One hundred and thirty asymptomatic volunteers (mean age, 48 years) met the inclusion criteria. The mean sagittal parameters in a normal Brazilian population were as follows: lumbar lordosis (LL) of 56.8°, pelvic tilt (PT) of 12.4°, pelvic incidence (PI) of 49.4°, PI-LL of -7.4°, T1 pelvic angle (TPA) of 8°, sagittal vertical axis (SVA) of -0.54 cm and T1 slope of 25.2°. Subjects ≥60 years old had significantly higher values of SVA (p=0.024) and TPA (p=0.009) than the two younger age groups. The TPA was significantly correlated with the following spinopelvic parameters: LL (r=-0.172, p=0.005), PT (r=0.776, p<0.001), PI (r=0.508, p<0.001), PI-LL (r=0.717, p<0.001), SVA (r=0.409, p<0.001) and T1 slope (r=0.172, p=0.050).

Conclusion: This study demonstrated significant physiologic trunk inclination with increasing age. The TPA, an angular parameter of global spinal alignment, presented a chain of correlations with different spinal segments.