Objective analysis of anthropometric parameters of the auricle in health and disease

Background: The auricle is a prominent anatomical feature of the face, and its distinct shape and symmetry make auricular deformities, such as microtia, highly noticeable. Microtia not only affects patients’ auditory function and facial aesthetics but can also have a profound impact on the psychological well-being of affected children. Due to the complex morphology of the auricle, our understanding of the underlying mechanisms of auricular malformations remains limited, and there is a lack of standardized methods for evaluating auricular shape, which hinders the objective assessment of treatment outcomes. Therefore, it is crucial to investigate the pathogenesis of auricular anomalies and to develop objective tools for quantifying auricular morphology to improve the diagnosis and management of these onditions.
Methods: In Part I, we explored the molecular mechanisms underlying MPA (mycophenolic acid)-induced microtia using bioinformatics analysis and human genetic databases. Part II involved a systematic review of classification systems and measurement methods for auricular deformities, summarizing objective measurement techniques used in microtia, auricular reconstruction, and prominent ear correction. In Part III, we developed a novel automated 3D surface-based auricle measurement algorithm, compared it with traditional manual methods, and validated its performance using a larger database of normal individuals to assess bilateral auricular differences.
Results: Our research revealed that MPA may induce auricular malformations by inhibiting MDM2, thereby increasing p53 activity, which leads to neural crest cell (NCC) apoptosis and subsequent ear development defects. The systematic review identified that current objective assessment techniques primarily focus on parameters such as auricular length, width, auriculocephalic angle, protrusion, and bilateral symmetry. These metrics play a critical role in the classification and evaluation of auricular deformities. Our developed automated measurement software demonstrated significantly higher precision than traditional manual methods, with improvements ranging from 5x to 54x across various parameters. Additionally, our automated measurement algorithm provided objective quantification of bilateral asymmetry and maintained high accuracy under both high- and low-radiation CT settings, revealing subtle asymmetries undetectable by manual measurements.
Conclusion: This study advances our understanding of the pathogenesis of auricular anomalies and introduces an innovative, high-precision automated auricular measurement algorithm for the objective assessment of auricular shape. Our findings underscore the urgent need for standardized classification systems and objective evaluation tools for treatment outcomes of auricular anomalies. The software developed in this study enables clinicians to assess auricular morphology with greater precision, providing a robust basis for clinical decision-making. Future research should focus on validating the software using 3D optical scanners to eliminate radiation exposure and achieve consistent measurement precision across different imaging modalities, ultimately establishing a new standard for the diagnosis and evaluation of auricular deformities.