Study on facial asymmetry in children under 16 years from the North West of England using three-dimensional images (3dMD)

• Main Author: Carty, Orla
• Other Authors: Flannigan, N. ; Burnside, G. ; Dominguez-Gonzalez, S.
• Published: University of Liverpool 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.762806

Objectives: The primary objective was to determine the extent of facial asymmetry in a standard population of children from the North West of England using a landmark based approach on 3-dimensional (3d) images. The secondary objectives were to investigate the direction and severity of nose and chin deviation and the correlation between them, to determine the relationship between gender and facial asymmetry and to investigate if asymmetry differs with age. Design/Setting: A retrospective cross-sectional cohort study undertaken at Alder Hey Children's Hospital. Subjects: Participants were children of either gender and under 16 years of age (mean 7.36 years) with all types of skeletal relationships who volunteered to have 3d images (using 3dMD software) of their head and face captured for research purposes. Methods: Images of 145 children were available. Following the application of exclusion criteria and a panel assessment including 2 Orthodontic Registrars, 2 Orthodontic Consultants and a Medical Illustration Technician, to determine adequate quality, 107 images were included in the study. Reference frame analysis was completed to orientate the images in a standardised manner. A landmark based approach was used by a single examiner positioning 8 mid and 7 bilateral facial landmarks and the analysis was applied using Vultus software (version 2.5.0.1). Intra and inter-reliability of landmark positioning were completed prior to data collection. Results: Fifty-seven males and 50 females were included with a mean age of 7.36 years (SD 3.74). The majority of the sample was White British (82.2%). The median asymmetry indices (AI) for midfacial landmarks were all < 1.10mm (25th and 75th IQR ranged from 0.24 to 1.75) and for bilateral facial landmarks were all < 2.60mm (25th and 75th IQR ranged from 0.63 to 3.65). Pogonion was the most asymmetric midfacial landmark (median AI 1.08mm, IQR 0.56, 1.75) and Cheilion was the most asymmetric bilateral facial landmark (median AI 2.56mm, IQR 1.69, 3.65). A statistically significant relationship between the side of nose and chin deviation (Chi-squared p=0.00) was detected and also a significant correlation between the severity of nose and chin deviation (Pearson's correlation 0.91). There was no significant difference in the asymmetry detected between males and females when the Mann-Whitney U test was applied. There was an association between increasing asymmetry and age for landmarks: Pronasale, Subnasale, Stomion, Pogonion and Christa philtri however this is potentially influenced by the size of the patient's head and thus should be interpreted with caution. Conclusions: In the standard population of children from the North West of England an element of facial asymmetry is present. The direction and magnitude of nose and chin deviation are highly correlated. Males and females exhibit equal levels of facial asymmetry.