Sagittal spinopelvic alignment in healthy Turkish adults: establishing normative radiographic reference values

Sagittal alignment of the spine and pelvis is critical for maintaining posture, balance, and mobility. Spinopelvic parameters-including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), and thoracic kyphosis (TK)-are essential for the evaluation and management of spinal deformities. Despite extensive global research, normative data for the Turkish population are lacking. This study aimed to establish spinopelvic reference values in healthy Turkish adults and to explore population-specific alignment characteristics.

This retrospective case-control study included 400 healthy adults (202 females, 198 males; mean age 40.2 ± 14.7 years) selected from 1,200 scoliosis radiographs obtained between 2016 and 2024. Standardized standing lateral radiographs were used to measure PI, PT, SS, LL, and TK. Measurements were independently performed by two orthopedic surgeons using the PACS system, and interobserver reliability was assessed via intraclass correlation coefficient (ICC).

Interobserver agreement was excellent for all parameters (ICC 0.947-0.978). The mean values were: PI 48.8° ± 8.9, PT 11.0° ± 6.2, SS 38.2° ± 6.4, LL 58.5° ± 8.2, and TK 37.3° ± 9.7. PI values were comparable to literature norms (p = 0.48), whereas PT and SS were significantly lower, and LL and TK significantly higher, compared to international reference values (p < 0.001 for all). Gender analysis revealed a moderate negative correlation with PI (r = - 0.526), while correlations between age and spinopelvic parameters were weak and clinically insignificant.

The Turkish adult population exhibits a distinct sagittal alignment profile, with lower PT and SS and higher LL and TK compared to established international norms. These findings underscore the necessity of incorporating regional normative data into clinical assessments and surgical planning to optimize patient-specific outcomes.