Current methods of assessing the accuracy of three-dimensional soft tissue facial predictions: technical and clinical considerations

Abstract

Since the introduction of three-dimensional (3D) orthognathic planning software, studies have reported on their predictive ability. The aim of this study was to highlight the limitations of the current methods of analysis. The predicted 3D soft tissue image was compared to the postoperative soft tissue. For the full face, the maximum and 95th and 90th percentiles, the percentage of 3D mesh points ≤2mm, and the root mean square (RMS) error, were calculated. For specific anatomical regions, the percentage of 3D mesh points ≤2mm and the distance between the two meshes at 10 landmarks were determined. For the 95th and 90th percentiles, the maximum difference ranged from 7.7mm to 2.2mm and from 3.7mm to 1.5mm, respectively. The absolute mean distance ranged from 0.98mm to 0.56mm and from 0.91mm to 0.50mm, respectively. The percentage of mesh with ≤2mm for the full face was 94.4–85.2% and 100–31.3% for anatomical regions. The RMS error ranged from 2.49mm to 0.94mm. The majority of mean linear distances between the surfaces were ≤0.8mm, but increased for the mean absolute distance. At present the use of specific anatomical regions is more clinically meaningful than the full face. It is crucial to understand these and adopt a protocol for conducting such studies.