Observational Study of Facial Rotation Patterns

Abstract

Background:Facial asymmetry is commonly observed during visual facial assessment and significantly influences aesthetic perceptions and emotional expressions. Although minor asymmetries are often seen as contributing to individual uniqueness and can be addressed with cosmetic injectables, pronounced disparities can necessitate medical intervention, particularly in fields such as orthodontics, facial, and reconstructive surgery. Pitch, roll, and yaw rotations, limited to the maxilla-mandibular complex movements have been observed. Facial rotation, as part of the facial ageing process, was previously reported along the x-axis only. Asymmetries around the y-axis and z-axis are not isolated, but are part of specific patterns.Objectives:This study is an observational study of facial rotation and asymmetry, present from birth, around the z-axis and the y-axis, across a diverse population of 340 individuals, emphasizing the identification of dominant patterns and their implications for aesthetic and functional outcomes.Methods:As part of the study validation, 'theoretical clarity' was provided by first defining the construct of facial rotation around the xyz axes. This was followed by an 'operational definition' of facial rotation, allowing how facial rotation could be measured by identifying specific facial asymmetry components. Two independent, non-medical team members were trained on the assessment of facial rotation and specific facial rotation components. Study participants included 340 adults, free from prior facial surgery, facial trauma, or cosmetic treatments (skin level treatments, injectables, and threads) encompassing 83 males and 257 females. High-resolution digital photography in standardized lighting conditions provided the data for assessing facial asymmetry and rotation. Image analysis categorized facial orientations into clockwise and counterclockwise rotations (z-axis), right-to-left rotation and left-to-right rotation (y-axis), with additional observations for variations/mixed components and non-rotational symmetries. An initial analysis of the photos and categorization of facial rotation was completed by the principal investigator. This was followed by a further, independent analysis by one of the non-medical team members. Results were compared and any discrepancies were resolved through consensus. After completing the photography and assessment of the 340th patient, and before analyzing the study results and performing statistical analysis, a second and final independent review of the uncoded images was completed by both the principal investigator and one of the independent non-medical team members, allowing for a second comparison of the results with any discrepancies resolved through consensus. This represented 'test-retest reliability' and 'inter-related reliability' to provide a further foundation for our observational facial rotation study validation.Results:The observation revealed that the predominant facial rotation was clockwise and left to right, components of which occurring in 87% of participants. Counter-clockwise rotation was less common, seen in only 6%, and minimal participants exhibited mixed components (2%) or no observable rotation (5%). These findings were consistent across sex and ethnicity. Test-retest reliability and inter-related reliability were high, validating this observational study method.Conclusion:Understanding the nuances of facial asymmetry through detailed rotational analysis provides a foundation for enhancing aesthetic evaluations and (non-)surgical planning. The study underscores the importance of recognizing and addressing facial asymmetry, and more specifically facial rotation patterns, in medical practice, contributing to better patient education and ultimately more tailored and effective treatments.