Sagittal Spinopelvic Alignment in Asymptomatic Iranian Adults Aged 18 to 40 Years.

BACKGROUND Recent studies have revealed the increasing importance of sagittal spinopelvic alignment. Knowing the values of sagittal spinopelvic parameters, which are affected by ethnicity, is essential in the normal asymptomatic population. In the current study, these parameters were measured in a sample of asymptomatic Iranian population. METHODS Seventy asymptomatic participants without complaint of musculoskeletal problems were enrolled. They had no complaint about musculoskeletal problems. Lateral full-length spinal and pelvic x-rays were taken. The following parameters were measured on x-rays and presented as mean ± standard deviation: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), lumbar tilt (LT) and thoracic tilt (TT). RESULTS The population consisted of 37 males and 33 females aged 26.6 ± 4.27 years. The mean values of PI, SS, PT, LL, TK, LT, and TT were 44.5 ± 10.1, 35.4 ± 6.7, 9.1 ± 7.9, 41.9 ± 14.7, 28.8 ± 8.3, 11.9 ± 7.4 and -7.5 ± 5.7 (median: -10; 5th percentile: -14; 95th percentile: 4.4) degrees, respectively. The variables were similar between males and females except for LL which was significantly higher in females (37.8 ± 16.5 versus 46.5 ± 11; P = 0.013). In addition, the linear regression model revealed age to be independently related with PI (beta = 0.344; P = 0.004) and PT (beta = 0.366; P = 0.002). PI (r = 0.344, P = 0.004) and PT (r = 0.359, P = 0.002) were positively correlated with age. Additionally, PI was positively correlated to SS, PT and LL and negatively to TT. CONCLUSION These findings may be used as referential values for sagittal spinopelvic parameters in the Iranian population. The positive correlation of PI with age questions the constancy of PI throughout life. However, larger studies are required.