Quantifying Normal Facial Form and Baseline Facial Asymmetry in the Pediatric Population
Min-Jeong Cho, M.D.1, Rami R. Hallac, Ph.D.1, Jananie Ramesh, B.S.1, James R. Seaward, M.D.1, Nuno V. Hermann, M.Sc., Ph.D.2, Tron A. Darvann, D.D.S., Ph.D.2, Angelo B. Lipira, M.D.3, Alex A. Kane, M.D.1.
1University of Texas Southwestern Medical Center, Dallas, TX, USA, 2University of Copenhagen, Copenhagen, Denmark, 3University of Washington, Seattle, WA, USA.
Restoring facial symmetry is an important objecttive in the treatment of many craniofacial conditions. Normal form has been measured using anthropometry, cephalometry, and conventional photography. In this study, we define normal facial form and baseline facial asymmetry using stereophotogrammetric images.
Stereophotogrammetric images (3dMD, Georgia, USA) of normal healthy children (n = 534) with no known cranial and facial abnormalities were recruited at well-child visits following IRB approval. The children ages ranged from 0 to 16 years old. A symmetric 3D template was registered and scaled to each individual scan using 25 manually placed landmarks. The template was deformed to each subject’s 3D scan using a thin-plate split algorithm and iterative closest point matching. Age based normal facial models were derived. Average facial asymmetry was calculated, with statistical characteristics of the population provided.
The mean facial asymmetry was 1.2 ± 0.6 % ranging from 0.4 to 5.4%. The mean asymmetry were equal between younger children (10 years), 1.2 ± 0.6% and 1.2 ± 0.6% respectively. In addition, similar asymmetry values were observed in African American and Caucasian children, 1.0 ± 0.5 % and 1.2 ± 0.7 %, respectively.
Understanding of the "normal" form and distribution of asymmetry in the normal condition is an important foundation in considering diagnosis and subsequent interventions in craniofacial conditions, which involve the face. In this study, we present a method to quantify facial normal form and baseline asymmetry in a large pediatric sample.
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