Correlation between pelvic tilt and the sacro-femoral-pubic angle in patients with adolescent idiopathic scoliosis, patients with congenital scoliosis, and healthy individuals

Hassan Ghandhari, Daniel Fadaei Fouladi, Mir Bahram Safari, Ebrahim Ameri

To examine whether the sacro-femoral-pubic (SFP) angle could estimate pelvic tilt (PT) in scoliotic and normal subjects. One hundred nine subjects including 38 patients with adolescent idiopathic scoliosis (AIS), 35 patients with congenital scoliosis (CS), and 36 healthy individuals were studied. PT, as the angle between the lines connecting the midpoint of the sacral plate to the centroid of one acetabulum and the vertical plane, and the SFP angle, as the angle between the midpoint of the upper sacral endplate, the centroid of one acetabulum, and the upper midpoint of the pubic symphysis, were calculated on full-length lateral and anteroposterior radiographs, respectively. Correlations between PT and the SFP angle were investigated in each group. The three groups were comparable in terms of age, sex, and the mean SFP angle. The mean PT, however, was significantly lower in healthy subjects compared to that in patients with AIS and CS. Significant and reverse correlations were present between PT and the SFP angle in all three groups (AIS: r = -0.32, p = 0.04, PT = 82.5 - average SFP angle; CS: r = -0.48, p = 0.003, PT = 95.41 - average SFP angle; healthy: r = -0.33, p = 0.04, PT = 88.95 - average SFP angle). Unlike two previous reports, the SFP angle correlated poorly to PT in this study, limiting its use as a suitable surrogate for PT in scoliotic and healthy subjects.