A scanographic study of asymmetry of the frontal process of zygoma in unilateral coronal synostosis.

INTRODUCTION: Unilateral coronal synostosis (UCS) is a complex craniosynostosis, combining malformations of the upper (frontal bone, orbito-naso-frontal bandeau (ONFB) ) and the middle thirds of the face. In our centre, the surgical correction consists in the repositioning of the ONFB in front of the zygomaticofrontal suture on the affected side. Defects in the corrections have been observed post-operatively for some patients with a persistent asymmetry in the side walls of the orbits. The purposes of our study were to perform an analysis of the frontal process of zygoma (FPZ) in children affected by UCS using preoperative CT-scans and to consider the modification of surgical techniques in order to achieve a better ONFB repositioning and thus, better symmetry.

MATERIAL AND METHOD: The preoperative CT-scans of 13 children with UCS who underwent corrective surgery in our department from 2005 to 2016, were analyzed. After the selection of 6 morphological points in 2 and 3 dimensions using planning software, the sutures constituting the coronal arch and the sagittal distances between the coronal plane and the zygomaticofrontal sutures were analyzed. We compared the measurements on the pathological side to the healthy side, the non-affected side being the reference side. The patients included were those for whom the lack of symmetry between the healthy side and the affected side was more than 2 mm. Statistical analyses were carried out using a Student t-test.

RESULTS: Of the 13 children, 10 (1 day to 42 months old) met the inclusion criteria. The mean sagittal distance between the coronal plane and the healthy zygomaticofrontal suture was 33.8 mm ± 5.43 mm [range: 25.9: 40.9] [median: 34.3]. On the pathological side, the distance was 28.75 mm ± 4.76 mm [range: 20.8: 36.3] [median: 29.55], (p = 0.04).

DISCUSSION: There is a significant asymmetry between the FPZ on the healthy and the pathological sides in children affected by UCS. This asymmetry is variable, therefore justifying a personalized surgical correction whichtakes into account not only the shape of the ONFB but also the degree of asymmetry of the FPZ. A prospective study with immediate preoperative CBCT image acquisition and long-term clinical and radiological follow-up, will be our next step.