Anterior synostotic plagiocephaly: a quantitative analysis of craniofacial features using computed tomography.

Abstract

Anterior synostotic plagiocephaly (ASP) is caused by the premature fusion of one coronal suture, which results in severe craniofacial asymmetry that can be challenging to correct. The various methods of the surgical procedures, as well as the distinctive facial characteristics of ASP, have been well documented. However, there is a paucity of literature pertaining to the quantitative analysis of the craniofacial features that are affected in ASP. This study used preoperative computed tomography (CT) scans to document and compare the morphometry of the anterior cranial fossa (ACF), orbit, and ear on the ipsilateral (synostotic) and contralateral (non-synostotic) sides in a select South African population of patients diagnosed with ASP. The dimensions of the ACF, orbit and the position of the ear on the ipsilateral and contralateral sides were measured using a set of anatomical landmarks on two-dimensional (2D) CT scans of 18 consecutive patients diagnosed with non-syndromic ASP. The differences between the ipsilateral and contralateral sides were computed and expressed as a percentage of the contralateral side. The findings of this study revealed that there was side-to-side asymmetry in the ACF, orbit, and ear. All ACF parameters decreased significantly (t-test; p<0.001) on the ipsilateral side when compared to the contralateral side, resulting in the volume of the ACF being the most affected (-27.7%). In terms of the orbit, on the ipsilateral side, the length-infraorbital rim (IOR), height, and surface area parameters increased significantly (t-test; p<0.001), with the height being the most affected (24.6%). The remaining orbital parameters (length-supraorbital rim (SOR), breadth and volume) decreased significantly (t-test; p<0.001), with the length-SOR parameter being the most affected (-10.8%). Furthermore, the ipsilateral SOR was noted to be displaced more cranially by an average of 3.89mm from the contralateral SOR. With regards to the position of the ipsilateral ear, it was found to be displaced anteriorly (9.33mm) and caudally (5.87mm) from the contralateral ear. This study augments the existing literature by providing actual values to corroborate the hallmark characteristics of ASP. These measures may help surgeons plan the technique and extent of surgical correction of the affected craniofacial structures during corrective surgery as it will provide them with an indication of the extent of the deformity on the ipsilateral side as compared to the contralateral side. The results of this study have the potential to propose a grading system in ASP patients according to severity of the condition if the sample size is increased.