Application of a Novel Semi-Automatic Technique for Determining the Bilateral Symmetry Plane of the Facial Skeleton of Normal Adult Males

Abstract

The accurate assessment of symmetry in the craniofacial skeleton is important for cosmetic and reconstructive craniofacial surgery. Although there have been several published attempts to develop an accurate system for determining the correct plane of symmetry, all are inaccurate and time consuming. Here, the authors applied a novel semi-automatic method for the calculation of craniofacial symmetry, based on principal component analysis and iterative corrective point computation, to a large sample of normal adult male facial computerized tomography scans obtained clinically (n = 32). The authors hypothesized that this method would generate planes of symmetry that would result in less error when one side of the face was compared to the other than a symmetry plane generated using a plane defined by cephalometric landmarks. When a three-dimensional model of one side of the face was reflected across the semi-automatic plane of symmetry there was less error than when reflected across the cephalometric plane. The semi-automatic plane was also more accurate when the locations of bilateral cephalometric landmarks (eg, frontozygomatic sutures) were compared across the face. The authors conclude that this method allows for accurate and fast measurements of craniofacial symmetry. This has important implications for studying the development of the facial skeleton, and clinical application for reconstruction.

Methodology for Morphometric Analysis of Modern Human Contralateral Premolars

“…There are a multitude of algorithms used to perform these automated surface analyses that are applied in similarity estimation and matching of 3D objects [259,260]. Recent studies have demonstrated that landmarkindependent methods had higher degrees of validity and reproducibility in addition to offering a more comprehensive analysis (Figure 7) compared to the landmark-dependent methods [258,261,262].…”

Convolutional Neural Networks and Geometric Moments to Identify the Bilateral Symmetric Midplane in Facial Skeletons from CT Scans

“…Alternatively, [ 4 ] determines the midline symmetry plane by using boney landmarks to create a midline representing facial symmetry. For a stack of horizontal lines crossing bilaterally through the facial skeleton containing boney landmarks, this approach essentially measures the midline symmetry plane as a perpendicular midpoint.…”

Mirroring Procedures for the Assessment of Asymmetry of Different Anatomical Structures of the Cranium: A Protocol Based on 3D-3D Superimposition

“…Other more innovative techniques are based on the determination of a midsagittal 11-12 Oct. 2017 plane according to the registration between the 3D model of cranium and its "mirrored" version [6]. The collocation of a midsagittal plane involves relevant difficulties as there are no universally accepted midpoints to guide a comparison between the two sides of the skull and manual methods for collocating a symmetry plane are affected by low reliability [18]. The present procedure solves this problem as the mirroring procedure is automatically performed by the software, reducing the possible error due to manual localization of the midsagittal plane.…”