Cranial deformation and deformational plagiocephaly (DP) in particular affect an important
percentage of infants. The assessment and diagnosis of the deformation are commonly carried by
manual measurements that provide low interuser accuracy. Another approach is the use of threedimensional
(3D) models. Nevertheless, in most cases, deformation measurements are carried out
manually on the 3D model. It is necessary to develop methodologies for the detection of DP that are
automatic, accurate and take profit on the high quantity of information of the 3D models. Spherical
harmonics are proposed as a new methodology to identify DP from head 3D models. The ideal
fitted ellipsoid for each head is computed and the orthogonal distances between head and ellipsoid
are obtained. Finally, the distances are modelled using spherical harmonics. Spherical harmonic
coefficients of degree 2 and order − 2 are identified as the correct ones to represent the asymmetry
characteristic of DP. The obtained coefficient is compared to other anthropometric deformation
indexes, such as Asymmetry Index, Oblique Cranial Length Ratio, Posterior Asymmetry Index and
Anterior Asymmetry Index. The coefficient of degree 2 and order − 2 with a maximum degree of 4 is
found to provide better results than the commonly computed anthropometric indexes in the detection
of DP.
