Three-Dimensional Cephalometric Landmarking and Frankfort Horizontal Plane Construction: Reproducibility of Conventional and Novel Landmarks.

Gauthier Dot,Philippe Rouch,Adeline Kerbrat,Laurent Gajny,Frédéric Rafflenbeul,Thomas Schouman

doi:10.3390/jcm10225303

Abstract

In some dentofacial deformity patients, especially patients undergoing surgical orthodontic treatments, Computed Tomography (CT) scans are useful to assess complex asymmetry or to plan orthognathic surgery. This assessment would be made easier for orthodontists and surgeons with a three-dimensional (3D) cephalometric analysis, which would require the localization of landmarks and the construction of reference planes. The objectives of this study were to assess manual landmarking repeatability and reproducibility (R&R) of a set of 3D landmarks and to evaluate R&R of vertical cephalometric measurements using two Frankfort Horizontal (FH) planes as references for horizontal 3D imaging reorientation. Thirty-three landmarks, divided into “conventional”, “foraminal” and “dental”, were manually located twice by three experienced operators on 20 randomly-selected CT scans of orthognathic surgery patients. R&R confidence intervals (CI) of each landmark in the -x, -y and -z directions were computed according to the ISO 5725 standard. These landmarks were then used to construct 2 FH planes: a conventional FH plane (orbitale left, porion right and left) and a newly proposed FH plane (midinternal acoustic foramen, orbitale right and left). R&R of vertical cephalometric measurements were computed using these 2 FH planes as horizontal references for CT reorientation. Landmarks showing a 95% CI of repeatability and/or reproducibility > 2 mm were found exclusively in the “conventional” landmarks group. Vertical measurements showed excellent R&R (95% CI < 1 mm) with either FH plane as horizontal reference. However, the 2 FH planes were not found to be parallel (absolute angular difference of 2.41°, SD 1.27°). Overall, “dental” and “foraminal” landmarks were more reliable than the “conventional” landmarks. Despite the poor reliability of the landmarks orbitale and porion, the construction of the conventional FH plane provided a reliable horizontal reference for 3D craniofacial CT scan reorientation.

Highlights

Diagnosis and planning of orthodontic and maxillofacial treatments rely heavily onX-ray imaging
3D imaging makes it possible to assess complex asymmetry and to obtain highly accurate orthognathic surgery planning that can subsequently be used for the manufacturing of surgical guides [1,2,3,4,5]
Exclusion criteria were refusal to participate in the research and lack of Computed Tomography (CT) scan segmentation

Summary

Introduction

Diagnosis and planning of orthodontic and maxillofacial treatments rely heavily on. Two-dimensional (2D) X-rays are routinely used but result in a flattening of three-dimensional (3D) craniofacial structures. In some clinical cases of dentofacial deformities—especially patients undergoing surgical orthodontic treatments (orthognathic surgery)—Computed Tomography (CT) or Cone Beam CT (CBCT) scans are useful [1]. 3D imaging makes it possible to assess complex asymmetry and to obtain highly accurate orthognathic surgery planning that can subsequently be used for the manufacturing of surgical guides [1,2,3,4,5]. The diagnostic value of these scans would increase if they could be used to perform 3D cephalometric analysis, which would require the localization of landmarks [8]. No set of 3D landmarks has been deemed sufficiently reproducible and repeatable for 3D cephalometry [8,9]

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Conclusion