The influence of involuntary facial movements on craniofacial anthropometry: a survey using a three-dimensional photographic system

Abstract

PurposeIn the modern anthropometry of complex structures, such as the face, different technical approaches for three-dimensional (3D) data acquisition have become increasingly more common. Results of meticulous evaluations have demonstrated a high level of precision and accuracy under both ideal and clinical circumstances.However, the question remains regarding which level of accuracy is adequate to meet clinical needs. Aside from the measuring technique itself, potential sources of error need to be identified and addressed. Involuntary facial movements in the subjects potentially influence clinical reliability. Materials and Methods The 3dMDfaceTM system was used in a clinical setting to investigate the influence of involuntary facial movements. Other factors of influence were systematically excluded. The mean technical error of the system (0.09 mm) was investigated in a previous study and taken into account for interpretation of the data. ResultsThe handling of the system was unproblematic for both data acquisition and data analysis. Including technical error and the influence of involuntary facial movements, the mean global error was 0.41 mm, with a range from 0.00 mm to 3.30 mm. Taking into account the technical error of the system known from the previous study, involuntary facial movements account for a mean error of 0.32 mm. ConclusionsThis range of involuntary facial movements clearly exceeds the known technical error of the utilized 3D photographic system. Given this finding, future 2 research should shift its focus from the analysis of the technical aspects of such systems to other influencing factors.

Intraoperative navigation for single-splint two-jaw orthognathic surgery: From model to actual surgery

“…Using the landmark method, the mean differences from the simulation to surgical outcome were less than 1 mm in this study. The results from the experiment indicate that the system is accurate for navigation and transferring virtual planning to actual surgery, and could meet the requirements for clinical application (Lübbers et al, 2012). There was no clear minimum requirement of accuracy for orthognathic surgery navigation in the literature.…”

“…There was no clear minimum requirement of accuracy for orthognathic surgery navigation in the literature. A 1.5-mm difference was used as a clinically acceptable standard (Sun et al, 2013a), which was described as unnoticeable discrepancy by the naked eye (Lübbers et al, 2012). Compared with previous registration methods, Sun et al presented an in vitro study using six anatomical landmarks as registration points with 85 target points in different maxillofacial areas and had a mean TRE of 0.93 mm.…”

Evaluation of 3 Different Registration Techniques in Image-Guided Bimaxillary Surgery

“…Thereby the patient's facial profile might be modified between CBCT acquisition and the surgical procedure. In addition, CBCT scan is taken while the patient is awake and has (unaware) mimic activity, 27 whereas laser surface scan is taken with the patient under anesthesia. Such soft-tissue changes are always interfering with accurate registration.…”

“…Based on the fact that in most facial soft-tissue structures, facial discrepancies less than 1.5 mm cannot be seen by the naked eye. 27 Therefore, we considered the registration result clinically acceptable when the TREs remained within 1.5 mm.…”

3D digital surface imaging for quantification of facial development and asymmetry in juvenile idiopathic arthritis

“…Several studies show the use of surface imaging in a clinical context with convincing results. [6][7][8] Main sources of error that typically influence the measurement are (1) the imaging device itself (system accuracy and reproducibility), 9 (2) the process of landmarking (the capability of recognizing and marking particular anatomical landmarks on the surface, either directly (manually) by a human operator or by some automatic algorithm), 10,11 (3) deformation of the face due to facial expression, 12,13 (4) spatial orientation of the face, and (5) determination of detailed point correspondence (interpolation between landmark locations; necessary in order to obtain values of e.g., development and asymmetry at every spatial location across the face). Error sources (4) and (5) have been less studied but are very dependent on the application.…”