Pelvic Incidence Angle in Standing, Maximal Anterior and Maximal Posterior Pelvic Rotation in a Sample of Healthy Subjects

This study aimed to investigate the differences in pelvic incidence (PI) between three standing, maximal anterior and maximal posterior pelvic rotation. This cross-sectional study was done on 150 healthy subjects. Lateral spine radiography was taken in 3 different positions in the same standard radiographic protocol. Sacral slope (SS) pelvic tilt (PT), lumbar lordosis (LL) and lumbosacral junction angle were measured by two independent, experienced spine surgeons. PI was calculated as sum SS and PT. The mean of PI in standing positions was 52.6±5.1, in anterior position was 52.6±5.5 and in posterior position was 52.3±5.2 degree. The mean of PI, PT, and SS in total and between male and female subjects was not statistically significant in three different positions (P>0.05). PI in 136 subjects (90.7%) is changed when the position was changed from standing to the posterior position, by mean of 2.06 degree. When the position was changed from standing to an anterior position, the change in PI degree was observed in 126 subjects (84%) by mean of 2.12 degree. Despite the none, significant value of PI in three different positions, a large number of subjects with a change in their PI when the position was changed to anterior or posterior (90.1%) position, show that PI can be varied by pelvic rotation in healthy adult subjects.