Estimation of sagittal pelvic orientation from frontal standard radiograph using the sacral-femoral-pubic angle: feasibility study in the pediatric population.

PURPOSE: Pelvic tilt is usually measured on a full spine sagittal view. The sacral-femoral-pubic angle (SFP) has been previously described as a reproducible method to estimate pelvic tilt on a pelvis AP view. The aim of our study is to determine the reliability of the extrapolated pelvic tilt (ePT) using the SFP angle in the pediatric population.
METHODS: We selected 240 full spine X-rays in our pediatric imaging database. The cohort was equally distributed according gender and age. The following parameters were measured: SFP angle on the AP view, pelvic tilt (PT), pelvic incidence (PI) and sacral slope (SS) on the sagittal view. Concordance between the measured pelvic tilt (mPT) and the calculated (ePT) value of PT was tested by a correlation test. Intra- and inter-observer reliability was tested for each parameter using ANOVA.
RESULTS: Our cohort included 240 children aged from 1 to 20 years (mean age 10.7 years). Mean SFP angle was 68.98° ± 6.8, mPT was 6.67° ± 8.56, ePT was 6.04° ± 6.79. The mean PI (45.04° ± 11.09) and SS (38.63° ± 8.12) were comparable to previously published pediatric data according to age groups. Intra- and inter-observer reliability showed acceptable correlation. Concordance between mPT and ePT was higher in older children (patients >10 years).
CONCLUSIONS: Estimated value of pelvic tilt using the SFP angle showed acceptable correlation to the pelvic tilt measured on sagittal view of the pelvis in children over 10 years. However, correlation rates were lower than previous publication in adult population. This simple method could accurately estimate the pelvic orientation on a single frontal view of the pelvis, which may be of particular interest in understanding the relationship between pelvic orientation and hip pathology. LEVEL OF EVIDENCE: IV.