Long-term positional changes of the mandibular proximal segment after IVRO using 3-D CT in facial asymmetry patients

Abstract

Objective: This study was to evaluate the long-term positional changes of the mandibular proximal segment including condyle in skeletal Class III patients with facial asymmetry after two-jaw orthognathic surgery (Le Fort I osteotomy + intraoral vertical ramus osteotomy) using three-dimensional computed tomography.Subjects and Methods: The subjects were composed of 17 skeletal Class III patients with facial asymmetry. CT images were taken at T1 (before surgery), T2 (1 year after surgery), and T3 (4 years after surgery) and measurements from the reconstructed three-dimensional (3D) CT images were done. The horizontal condylar angle (HCA) at horizontal slice image, coronal condylar long axis angle (CCLA) and coronal condylar vertical axis angle (CCVA) at coronal slice image, and sagittal condylar angle (SCA) and temporomandibular joint space distance (A-B and C-D) at sagittal slice image were measured on both deviated and non-deviated sides. Results: When comparing the bilateral differences at T1, the horizontal, coronal, and sagittal condylar angle were significantly different (P < .05). At T2, there was no significant difference except the horizontal condylar angle and at T3, there was no significant difference except the horizontal condylar angle and the coronal condylar vertical axis angle (P > .05).The most of measurements were significantly different during T1-T2, but there was no significant difference during T2-T3 (P < .0167). The horizontal condylar angle increased significantly at both sides during T1-T2, that showed outward rotation of condyle after IVRO (P < .0167). The coronal condylar long axis angle at non-deviated side and the coronal condylar vertical axis angle at deviated side decreased significantly during T1-T2 (P < .0167). The sagittal condylar angle decreased significantly at both sides during T1-T2 and the temporomandibular joint space distance (A-B and C-D) increased significantly that showed anterior-inferior movement of condyle after IVRO (P < .0167).Conclusion: In skeletal Class III asymmetry patients, the mandibular asymmetry improved after IVRO, and the most of measurements of the mandibular proximal segment showed no significant difference during the 4-year follow up period. After IVRO, three-dimensional displacement of the proximal segment represented outward rotation of condyle, medial displacement of the tip of the proximal segment on the deviated side for improving skeletal symmetry, posterior displacement of the tip of the proximal segment and anterior-inferior movement of condyle in each horizontal, coronal, and sagittal slice image. And we could observe that the mandibular proximal segments move to the more stable position while the function of the mandible recovered after surgery.