A standardized nomenclature for craniofacial and facial anthropometry

Abstract

Standardized terms and methods have long been recognized as crucial to reduce measurement error and increase reliability in anthropometry. The successful prior use of craniometric landmarks makes extrapolation of these landmarks to the soft tissue context, as analogs, intuitive for forensic craniofacial analyses and facial photogrammetry. However, this extrapolation has not, so far, been systematic. Instead, varied nomenclature and definitions exist for facial landmarks, and photographic analyses are complicated by the generalization of 3D craniometric landmarks to the 2D face space where analogy is subsequently often lost, complicating anatomical assessments. For example, landmarks requiring palpation of the skull or the examination of the 3D surface typology are impossible to legitimately position; similar applies to median landmarks not visible in lateral photographs. To redress these issues without disposing of the craniometric framework that underpins many facial landmarks, we provide an updated and transparent nomenclature for facial description. This nomenclature maintains the original craniometric intent (and base abbreviations) but provides clear distinction of ill-defined (quasi) landmarks in photographic contexts, as produced when anatomical points are subjectively inferred from shape-from-shading information alone.

Comparative Assessment of a Novel Photo‐Anthropometric Landmark‐Positioning Approach for the Analysis of Facial Structures on Two‐Dimensional Images

“…Indeed, these four specific landmarks are involved in the establishment of some of the most characteristic facial measurements , such as the facial height (N ‐ Gn), facial width (Zy ‐ Zy), mandibular width (Go ‐ Go), facial length index (N ‐ Gn/Zy ‐ Zy), mandibulo‐facial index (Go ‐ Go/Zy ‐ Zy), and naso‐chelion angle (Ch ‐ N ‐ Ch). The same observation has, nonetheless, already been reported in a number of previous studies and may be explained by the fact that the traditional cephalometric descriptions for these four landmarks largely rely on physical and/or bone structures, which are particularly difficult to detect on frontal images. As a proof, the opposite trend could actually be seen for landmarks such as Ch and Sto, for which traditional cephalometric definitions rely more strongly on facial structures visible on images .…”

“…Traditional cephalometric definitions, however, merely describe a series of purely anatomical structures lying on the skin surface and/or the underlying bones and were primarily established for the purpose of directly mapping actual living subjects or their lateral‐view X‐ray image for medical purposes . Consequently, their adoption in FPA applications usually leads to a high positioning variability within and between examiners . The main reason for this arises from the fact that different examiners may have different interpretations of where a specific cephalometric landmark should be placed on a two‐dimensional, frontal view, facial image, without any three‐dimensional reference and/or the possibility to touch the subject's actual facial surface.…”

A geometric morphometric evaluation of the Belanglo ‘Angel’ facial approximation

“…The foreshortening and widening of the face may also be due to photographic distortion, which causes the lower face to recede and the upper face to expand when the skull is photographed at distances of less than 2.5 m [38,39]. It also the case that errors in assigning the landmarks onto a 2D image [59] may have contributed to the resulting facial shape, and in particular at the mid-ramus and gonion. Had the fSTDs been applied directly onto the skull and subsequently photographed, as is recommended [60], then this would have reduced, but not entirely removed, the problem of photographic distortion and facilitated a more accurate landmark placement.…”

Automatic cephalometric landmarks detection on frontal faces: An approach based on supervised learning techniques

“…As described in [3] and [4], one expert manually located 28 cephalometric landmarks in all the 1000 images following the instructions steps described in [12]. The whole list of the selected landmarks, according to Caple and Stephan standard nomenclature [32], is the following: Endocanthion (en'), Exocanthion [33]. Figure 2 shows all selected landmarks location on the face, meanwhile the Table 1 presents the craniometric and photo-anthropometric landmarks groups, reiterating those landmarks are collected using frontal facial photos resulting in different localization in vivo.…”