This study aimed to describe the three-dimensional lower limb bone morphology of ambulant children with CP according to the type of CP and to evaluate their relation to gait kinematics.

One hundred and five ambulant children with CP (3–17 years old) underwent a biplanar X-Rays (EOS system) from which was extracted a full 3D bone model of their lower limbs. Moreover each child underwent a quantitative gait analysis from which was extracted the Gait Deviation Index (GDI). The limbs were divided into 3 groups: the more impaired side of the bilateral CP children (Bilat-CP, n=48), the affected limb (Unilat-CP, n=57) and the non-affected limb of the unilateral CP children (Control, n=57). The statistical analysis included a 2-factor analysis of variance (bone parameters and population), Principal Component Analysis (PCA) and focused PCA (fPCA).

Growth parameters (length) were most prominent factors of bone morphology compared to other morphological characteristics. The Neck-Shaft Angle (NSA) was significantly greater (+3.6°) in the Unilat-CP group in comparison with the Control group and the Femoral Torsion (FT) was significantly greater in the Bilat-CP group (+10.4°) in comparison with the Control group. Other 3D parameters were not significantly different among the 3 groups. fPCA centered on GDI showed no strong correlation between GDI and lower limb bone parameters, regardless of CP Type.

These data suggest the existence of specific loading issue inducing specific bone deformities depending on the CP type. However at the group level, the most determinant factor of the bone morphology of ambulant children with CP is the bone size in relation to growth. The poor relation between bone morphology and GDI incites to explore the link between specific bone parameters and specific gait parameters.