The Pelvic Incidence Stratified Sagittal Spinopelvic Alignment in Asymptomatic Chinese Population With Different Age Groups

Study Design: Cross-sectional study. Objective: To provide the age- and pelvic incidence-related variations of sagittal alignment in asymptomatic Chinese population. Methods: This study recruited asymptomatic adult subjects. All subjects undertook the standing whole spinal radiograph and the sagittal parameters were measured: sagittal vertical axis (SVA), T1 pelvic angle (TPA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic incidence (PI) and pelvic tilt (PT). All subjects were divided into young, middle aged and elderly groups, then each age group was further divided into 5 subgroups (very low, low, average, high and very high) based on PI values. The relations between PI, age and other parameters were evaluated. The differences in sagittal parameters of each PI subgroup were compared. Results: 546 subjects were included with an average age of 38.6 years (18 to 81). The number of subjects over 70 years and with very low PI was relatively small. The average of PI, TPA, PT and LL were 45.9 degrees +/- 8.4 degrees, 6.4 degrees +/- 6.2 degrees, 11.9 degrees +/- 6.6 degrees and 49.2 degrees +/- 10.1 degrees, respectively. SVA, TPA, TK and PT increased with age (P < 0.05), while SVA, TPA, PT, PI-LL also increased with PI (P < 0.05). LL, PT, TPA, PI-LL and LL-TK were different among the 5 PI subgroups (P < 0.05). However, the values of LL in elderly subjects with high and very high PI were similar. Conclusion: The age- and PI-related variations in sagittal alignment of Chinese population were provided. The sagittal parameters were significantly influenced by age and PI. The individual pelvic morphology should be carefully considered during the assessment and restoration of sagittal balance.