Identifying Three-Dimensional Facial Fluctuating Asymmetry in Normal Pediatric Individuals: A Panel Assessment Outcome Study of Clinicians and Observers.

Pang-Yun Chou,Rafael Denadai,Alex A Kane,Lun-Jou Lo,Rami Hallac,Hsiao-Jung Tseng,Chih-Kai Hsu,Sheng-Wei Wang,Shih-Heng Chen,Chih-Hao Chen

doi:10.3390/jcm8050648

Abstract

This study measured three-dimensional facial fluctuating asymmetry in 600 normal and healthy Taiwanese individuals (6 to 12 years old) and assessed the perceptions of increasing levels of facial fluctuating asymmetric severity by using a panel composed of 20 clinicians (surgical professionals), as well as 20 adult and 40 pre-adolescent observers. On average, this normal cohort presented a facial fluctuating asymmetry of 0.96 ± 0.52 mm, with 0.52 ± 0.05, 0.67 ± 0.09, 1.01 ± 0.10, and 1.71 ± 0.36 mm for levels I, II, III, and IV of severity, respectively. For all categories of raters, significant differences in the average symmetry–asymmetry scale values were observed, with level I < level II < level III = level IV (all p < 0.01, except for level III vs. IV comparisons with p > 0.05). For level I, pre-adolescent observers presented a significantly (p < 0.05) higher symmetry–asymmetry scale value than adult observers, with no significant (all p > 0.05) differences for other comparisons. For overall facial asymmetry and levels II, III, and IV, no significant (all p > 0.05) differences were observed. This study reveals that the normal pediatric face is asymmetric and the panel assessment of facial fluctuating asymmetry was influenced by the level of severity and the category of raters and contributes to the literature by revealing that pre-adolescent raters present a similar or higher perception of facial asymmetry than adult raters.

Highlights

From an ecology and evolutionary biology standpoint, perfect bilateral symmetry is defined as the optimal outcome of the development of bilateral traits in the absence of perturbations [1]
Since the restoration of symmetry is the main goal of facial asymmetric deformity reconstruction, establishing facial fluctuating asymmetry by specific ethnic and age groups is crucial as it may be adopted as a target of treatment as well as applied as normative data for genetics, orthodontics, and surgical disciplines [6,7,8,9,10,11]
Contrary to our initial hypothesis, plastic surgeons exhibited no significant differences for perceptions of facial symmetry–asymmetry in all levels of severity, compared with adults and pre-adolescent observers. These findings revealed that various levels of facial fluctuating asymmetry were identified or perceived by lay observers, who had no expertise in evaluating facial asymmetries

Summary

Introduction

From an ecology and evolutionary biology standpoint, perfect bilateral symmetry is defined as the optimal outcome of the development of bilateral traits in the absence of perturbations [1]. When facial asymmetry is clinically obvious (called facial asymmetric deformity, which is more commonly directional rather than fluctuating), surgical or nonsurgical treatment may be required [3,4,5]. Since the restoration of symmetry is the main goal of facial asymmetric deformity reconstruction, establishing facial fluctuating asymmetry by specific ethnic and age groups is crucial as it may be adopted as a target of treatment as well as applied as normative data for genetics, orthodontics, and surgical disciplines [6,7,8,9,10,11]. For human faces, which are complex structures, these 3D image capturing systems offer a number of distinct advantages, including minimal invasiveness; quick capture speed; the ability to archive images for subsequent analyses; high-quality images without distortion of spatial form, shape, and size, resulting in a lifelike rendering; a realistic facial view with images moving from one side to the other; and a high degree of reproducibility, reliability, and validity [12,13,14,15]

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