Evaluation of demographic factors affecting predictability of the sacro-femoral-pubic angle in healthy adolescents

The objectives of the present study are to evaluate the correlation between pelvic tilt (PT) and the sacro-femoral-pubic (SFP) angle in Asian healthy adolescents, to provide the normal value of SFP angle as reference data in Asian adolescents, and to clarify whether the predictability of PT could be affected by gender and ontogenesis. In all, 100 girls with a mean age of 12.66years (range 8-18years) and 70 boys with a mean age of 13.35years (range 8-18years) were recruited in this retrospective study. SFP angles and PT were obtained on long-cassette standing upright radiographs. The subjects were grouped based on age. Independent-sample t-tests were performed to compare age, SFP angle, and PT between genders. In all age groups, the relationship between SFP angle and PT was analyzed by Pearson's correlation analysis and linear regression analysis, respectively. Reliability analysis showed high intra- and inter-observer agreements in PT and SFP, with an intra-class correlation coefficient (ICC) >0.8. SFP angle averaged 71.64 degrees +/- 4.91 in all the normal subjects, of which the mean PT was 72.03 degrees +/- 4.94 in the female group and 71.09 degrees +/- 4.83 in the male group. SFP and PT were strongly correlated in all the age groups according to Pearson's correlation analysis. The overall coefficient was 0.679 in girls and 0.584 in boys. The present study is the first to describe the normal value of SFP angle in healthy Asian adolescents to serve as a reference data. In all age groups, SFP angles can be used to predict PT when lateral radiographs do not permit assessment of PT. The predictability of SFP angle for PT was not affected by gender or maturation status.