Both the Observer’s Expertise and the Subject’s Facial Symmetry Can Affect Anatomical Position of the Head

Publication date: Available online 11 October 2018

Source: Journal of Oral and Maxillofacial Surgery

Author(s): Peter H. Sutton, Jamie Gateno, Jeryl D. English, Jaya Paranilam, John F. Teichgraeber, James J. Xia

ABSTRACT

Purpose

It is easier for us to judge facial deformity when the patient's head is in anatomic position. The purposes of this study were to determine: 1) if a group of expert observers agree more than a group of non-experts on what is the correct anatomical position of the head, 2) whether there is more variation in the alignment of an asymmetrical face compared with a symmetrical one, and 3) whether the alignments of experts are more repeatable than those of non-experts.

Subjects

and Methods: Thirty-one orthodontists (experts) and 31 dental students (non-experts) were recruited in this mixed-model study. They were shown randomly oriented three-dimensional head photographs of a symmetrical adult and an asymmetrical adolescent. In a viewing software, the observers oriented the images into anatomical position. They repeated the orientations 4 weeks later. The data was analyzed using a Generalized Linear Model and Bland-Altman plots. The primary predictor variables were experience and symmetry status. The outcome variable was anatomical position of the head. The other variables of interest included time, and orientational direction.

Results

There was a statistically significant difference between the measurements completed by experts and non-experts [F(1,60)=14.83, P<0.01]. The interaction between expertise and symmetrical status showed that there was a statistically significant difference between symmetrical and asymmetrical faces in both expert and non-expert groups [F(1,60)=9.93, P=0.003]. The interaction between expertise and time showed a statistically significant difference in measurement over time in both the expert and non-expert groups [F(1,60)=4.66, P=0.03].

Conclusions

The study shows that experts can set a head into anatomical position better than non-experts. Besides, facial asymmetry has a profound effect on the ability of an observer to align a head in the correct anatomical position. Finally, observer-guided alignment is not reproducible.

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