Normative Thoracic, Lumbar, Pelvic, and Global Sagittal Alignment Parameters for Asymptomatic Adults

STUDY DESIGN: Systematic review and meta-analysis. OBJECTIVE: To describe regional and global spinopelvic sagittal parameters in asymptomatic adults. SUMMARY OF BACKGROUND DATA: Understanding normal alignment is important for management of patients with spinal deformities and essential for patient well-being following corrective surgery. To our knowledge, there exists no meta-analyses on normative alignment. MATERIALS AND METHODS: We searched PubMed for primary studies on asymptomatic individuals with normal spinal anatomy and no prior spinal intervention. The collected variables included: age, gender percentage, global thoracic kyphosis (T1-3-T12 TK), regional TK (T4-5-T12), lumbar lordosis to L5 (T12-L1-L5, LL-L5), LL to S1 (T12-L1-S1, LL-S1), sacral slope (SS), pelvic incidence (PI), pelvic tilt (PT), PI-LL mismatch, sagittal vertical axis (SVA), T1 pelvic angle (TPA), and spinosacral angle (SSA). Data was analyzed according to sex, age (20-40 vs. 40-60 vs. greater than 60 yrs), ethnic group (Asian, Caucasian, Hispanic, and Middle Eastern), and Asian subgroup (Chinese, Japanese, and Korean). RESULTS: A total of 191 articles from 27 countries including 35,913 participants were reviewed: 16,125 men (44.9%), 18,222 women (50.7%), age range: 18 to 93 years were included. Regional TK and PT increased significantly in patients >60 compared with other groups. Globally, SVA, TPA, and changed with age in patients >60. CONCLUSION: LL-S1, PI and PT were all higher in women. Regional TK, PT, PI-LL, SVA, and TPA all increased with age, while LL-S1 and SSA decreased. Global TK, regional TK, LL-S1, PI, and PI-LL all had significant differences across broad ethnic groups, and LL-S1, PI, PT, and SVA showed differences within the Asian subgroup. Global alignment was largely equivalent across ethnic groups.