Abstract：
The aims of this study were to analyze the morphological changes of the mandibular angle after orthognathic surgery for mandibular setback and investigate related factors. This retrospective study included patients from January 2017 to December 2021 diagnosed with skeletal class III deformity who underwent BSSRO (Group I) or bimaxillary surgery (Group II). Preoperative (T0), within 1 month postoperatively (T1), and 6 months postoperatively (T2) CT scans were collected from 61 patients to three-dimensionally analyze the proximal segment displacement, the linear and angular changes of the mandibular angle. The gonion points moved posteriorly and laterally (P < 0.001), while the inferior movement was not significant (P = 1.000, P = 0.274). The intergonial width increased by 3.32 ± 1.87 mm and 2.34 ± 1.77 mm as revealed by T2 CTs, respectively, in Group I and Group II. Mandibular angle decreased in both groups and by 1.41 ± 2.95° in Group I and 1.37 ± 3.41° in Group II. The increase in intergonial width between T1 and T0 was negatively correlated with the preoperative mandibular angle (P = 0.003) and positively correlated with the transverse outward movement of the proximal segment (P < 0.001). After surgery, the intergonial width increased and the inferior and posterior border of the proximal segment flared outward. The changes in intergonial width and mandibular angle were mainly related to the rotation of the proximal segment, which has a certain impact on the aesthetics of the lower face. Therefore, controlling the position of the proximal segment is of vital importance to lessen the changes in the mandibular angle area.Level of Evidence III. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .
摘要：
本研究旨在分析正颌手术后下颌角的形态学变化，并探讨相关因素。这项回顾性研究包括2017年1月至2021年12月诊断为骨骼III类畸形并接受BSSRO（I组）或双颌骨手术（II组）的患者。术前(T0),术后1个月内（T1），术后6个月（T2）的CT扫描收集了61例患者，以三维分析近端移位，下颌角的线性和角度变化。角点向后和横向移动(P<0.001)，而下位运动不显著(P=1.000,P=0.274)。T2CT显示，间隙宽度增加了3.32±1.87mm和2.34±1.77mm，分别,第一组和第二组。下颌角在两组中均减小，在I组中减小了1.41±2.95°，在II组中减小了1.37±3.41°。T1～T0间间隙宽度的增加与术前下颌角呈负相关(P=0.003),与近端节段横向向外移动呈正相关(P<0.001)。手术后,间隙宽度增加，近端段的下缘和后缘向外张开。间隙宽度和下颌角的变化主要与近端节段的旋转有关，这对下脸的美学有一定的影响。因此,控制近端节段的位置对于减少下颌角区域的变化至关重要。证据等级III。该期刊要求作者为每篇文章分配一定程度的证据。对于这些循证医学评级的完整描述，请参阅目录或在线作者说明www。springer.com/00266.
