Three-dimensional assessment of facial asymmetry in children with operated unicoronal synostosis

Abstract

Objectives: The primary objective was to quantitatively describe soft tissue middle and lower third facial asymmetry and facial rotation in children with Unicoronal synostosis (UCS) who have undergone surgical correction with Fronto-orbital Advancement and Remodelling (FOAR) in infancy using three-dimensional stereophotogrammetric imaging. The secondary objective was to assess if a correlation exists between facial asymmetry and age of imaging or age of surgical intervention. Design/ Setting: A retrospective cross-sectional study undertaken at Alder Hey Craniofacial Unit, Liverpool. Subjects: Children with nonsyndromic UCS who underwent Fronto-orbital Advancement and Remodelling in infancy and had post-operative 3D imaging with the static 3dMD head system. Methods: Participants with nonsyndromic UCS and who underwent FOAR at Alder Hey Craniofacial Unit in infancy were identified. The quality of their static 3dMDhead images were assessed for inclusion in the study. Twenty two anthropometric landmarks were identified (eight mid-facial and seven paired bilateral landmarks) for each participant on the static 3dMDhead images. The landmarks were remarked on a random sample of 24 images to assess intra-rater and inter-rater reliability by two investigators. An asymmetry index (AI) was calculated for each landmark and linear and surface measurements between each of the paired bilateral landmarks and the landmark Nasion were measured. Deviation of the nasal tip and chin were also measured to assess the direction of facial rotation. Results: Thirty six participants were included for analysis. The mean age of FOAR was 1yr 5 months and the average age of 3D imaging was 5yrs 6months. Intra-class correlation coefficients showed excellent agreement (ICC 0.96-0.99) for all landmarks with the exception of Nasion in the x direction which had good agreement (intra-rater ICC 0.66 and inter-rater ICC 0.77). The asymmetry index showed that facial asymmetry was evident in the middle and lower face and increased as you move superiorly to inferiorly away from the cranium. The AI was lowest for the landmark Nasion (0.49mm) and highest for Cheilion (7.11mm). The amount of asymmetry was generally greater in the medio-lateral direction. Average deviation of the nasal tip and Pogonion to the unfused side was 4.4 ± 3.9 degrees and 3.5 ± 2.7 degrees respectively. Significant facial rotation of the middle and lower face towards the unfused side was evident (Chi-square analysis, p < 0.001). Age of imaging and age of surgical intervention did not correlate with facial asymmetry. Conclusions: The findings of this study demonstrate that children with UCS who undergo FOAR in infancy show consistent soft tissue facial asymmetry post-operatively. FOAR does not change the direction of facial growth with continuation of the UCS phenotype of facial rotation towards the unfused side.