Evaluating fluctuating and directional asymmetry in postnatal petrous bone growth: a 3D morphometric study.

PURPOSE: The objective was to assess fluctuating asymmetry (FA) and directional asymmetry (DA) of the petrous bone (PB) and the petromastoid V (PMV) in children using 3D morphometric data.

METHODS

CT scans of normal children (0 to 30 months) were included. After segmentation, the geometric characteristics were calculated (volume, three inertial semi-axes (ISA), centroid, distance, angle). The FA and DA were studied according to stages of postural development and sex.

RESULTS

116 CT scans were studied (70 boys, 46 girls). The two sides of the PB and PMV were symmetric (FA between 1.87% and 3.01%). PB volumes showed FA along the stages of postural development (p = 0.034) and were sex-independent. No FA was found for the 3D shape of the PB, but there was a DA for the 3rd ISA of the right side (p = 0.017). The FA of the PMV was greater in boys. A DA of the PMV (p = 1.17 e−11) (distance from the CS = left > right) was present in boys regardless of the stages of postural development.

CONCLUSION

Changes in posture did not influence PB and PMV geometry and symmetry. However, a FA appeared in PB volume. Moreover, we highlighted a right DA for PB and PMV.