Three-dimensional morphologic study of the child's hip: which parameters are reproducible?

Three-dimensional evaluation of skeletal deformities of the pelvis and lower limbs in ambulant children with cerebral palsy

Skeletal abnormalities, affecting posture and walking pattern, increase with motor impairment in children with cerebral palsy (CP). However, it is not known whether these skeletal malalignments occur in children with slight motor impairment. Our aim was to evaluate skeletal malalignment at the level of the pelvis and lower limbs in ambulant children with CP, with slight motor impairment, using a low dose biplanar X-ray technique. Twenty-seven children with spastic CP (mean age: 10.9±4years, 7 Hemiplegia, 20 Diplegia, GMFCS levels I:17, II:10), with no previous treatments at the hips and knees, underwent EOS(®) biplanar X-rays. A control group consisting of 22 typically developing children was also included. Three-dimensional reconstructions of the pelvis and lower limbs were performed in order to calculate 11 radiological parameters related to the pelvis, acetabulum and lower limbs. Pelvic incidence and sacral slope were significantly increased in children with CP compared to TD children (48°±7° vs. 43°±8°, 42°±7° vs. 38°±5°, respectively, p=0.003). Acetabular parameters did not significantly differ between the two groups. Femoral anteversion and neck shaft angle were significantly increased in children with CP (25°±12° vs. 14°±7°, p<0.001; 134°±5° vs. 131°±5°, p=0.005 respectively). No difference was found for tibial torsion. This study showed that even slightly impaired children with CP have an anteverted and abducted femur and present positional and morphological changes of the pelvis in the sagittal plane. The orientation of the acetabulum in 3D seems to not be affected when children with CP present slight motor impairment.

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.