Three-dimensional facial morphometry: From anthropometry to digital morphology

Abstract

Several basic and clinical disciplines are interested in the quantitative assessment of the dimensions of human facial soft-tissue structures (eyes, nose, mouth and lips, chin, ears), and of their reciprocal spatial positions and relative proportions. Anatomical and anthropometric descriptions, medical evaluations (genetics; maxillo-facial, plastic and esthetic surgery; dentistry), forensic medicine, they all need reference three-dimensional data collected on healthy, normal individuals selected for sex, age, ethnic group, to be compared to those obtained on the single patient. Data collection should be made non-invasively, rapidly, simply, directly on the subjects using low-cost instruments. All data should be digital, thus entering computerized data bases that can be used to visualize and simulate treatment. Currently, in clinical investigations and research classic direct anthropometry is being replaced with various three-dimensional image analyzers. Optical, non-contact digitizers (mainly, laser scanners and stereophotogrammetric devices) perform a fast digitization of the face, providing a detailed analysis of the soft-tissue surface. Contact instruments (electromagnetic and electromechanic digitizers) digitize discrete soft-tissue facial landmarks. Subsequently, landmark coordinates are used into mathematical and geometric models of the face, and angles, distances and ratios similar to those measured in conventional anthropometry can be obtained. Additionally, multivariate methods of analysis, obtained either from geometric morphometry or from other analytical methods, could be used. Overall, computerized instruments seem sufficiently reliable, simple and fast to be used also within clinical contexts, thus providing useful quantitative information to allow a better patient care, without submitting the subjects to potentially harmful procedures.