Use of spherical coordinates to evaluate three-dimensional facial changes after orthognathic surgery

Abstract

PurposeThis study aimed to assess the three-dimensional (3D) facial changes after orthognathic surgery by evaluating the spherical coordinates of facial lines using 3D computed tomography (CT).Materials and MethodsA 19-year-old girl was diagnosed with class III malocclusion and facial asymmetry. Orthognathic surgery was performed after orthodontic treatment. Facial CT scans were taken before and after orthognathic surgery. The patient had a menton deviation of 12.72 mm before surgery and 0.83 mm after surgery. The spherical coordinates of four bilateral facial lines (ramal height, ramal lateral, ramal posterior and mandibular body) were estimated from CT scans before and after surgery on the deviated and opposite side.ResultsThe spherical coordinates of all facial lines changed after orthognathic surgery. Moreover, the bilateral differences of all facial lines changed after surgery, and no bilateral differences were zero.ConclusionThe spherical coordinate system was useful to compare differences between the presurgical and postsurgical changes to facial lines.

Amount of Facial Asymmetry in a Spherical Coordinate System: A Comparison Before and After Orthognathic Surgery

“…This result was consistent with previous reports that some level of asymmetry can remain even after orthognathic surgery [13,15,18,21]. Jung et al [18] reported that surgical results of facial asymmetry correction seemed to be clinically acceptable.…”

“…The skeletal asymmetry after surgery has been rarely studied. A case report showed that skeletal asymmetry remained after surgery in a different form from that before surgery [13]. This study aims to analyze the amount of asymmetry of facial lines before and after orthognathic surgery using spherical coordinate system on 3D CT.…”

“…The menton deviation was significantly reduced by surgery (preoperative 7.67mm±4.46mm, postoperative 2.17mm±1.58mm, p<.05). It showed that orthognathic surgery may recover facial symmetry by repositioning of the Me which is an index to classify facial asymmetry [13,19,20].…”

“…There have been many studies for developing the evaluation methods of facial asymmetry using 3D CT. However the evaluation method of facial asymmetry has not yet been established [8][9][10][11][12][13].…”

“…An alternative spherical coordinate system was developed from the geographic coordinate system for analyzing facial lines and asymmetry [12][13][14]. Three-dimensional analysis of facial asymmetry can be effectively achieved by using a spherical coordinate system(v,θ,ϕ) of 3D facial lines, where v is length, θ midsagittal inclination angle, and ϕ coronal inclination angle.…”