Morphological Changes of the Mandibular Angle After Orthognathic Surgery with Class III Deformity in East Asia

The aims of this study were to analyze themorphological changes of the mandibular angle afterorthognathic surgery for mandibular setback and investi-gate related factors. This retrospective study includedpatients from January 2017 to December 2021 diagnosedwith skeletal class III deformity who underwent BSSRO(Group I) or bimaxillary surgery (Group II). Preoperative(T0), within 1 month postoperatively (T1), and 6 monthspostoperatively (T2) CT scans were collected from 61patients to three-dimensionally analyze the proximal seg-ment displacement, the linear and angular changes of themandibular angle. The gonion points moved posteriorlyand laterally (P\0.001), while the inferior movement wasnot significant (P= 1.000,P= 0.274). The intergonialwidth increased by 3.32 +/- 1.87 mm and 2.34 +/- 1.77 mmas revealed by T2 CTs, respectively, in Group I and GroupII. Mandibular angle decreased in both groups and by1.41 +/- 2.95 degrees in Group I and 1.37 +/- 3.41 degrees in Group II. Theincrease in intergonial width between T1 and T0 wasnegatively correlated with the preoperative mandibularangle (P= 0.003) and positively correlated with thetransverse outward movement of the proximal segment(P\0.001). After surgery, the intergonial width increasedand the inferior and posterior border of the proximal segment flared outward. The changes in intergonial widthand mandibular angle were mainly related to the rotation ofthe proximal segment, which has a certain impact on theaesthetics of the lower face. Therefore, controlling theposition of the proximal segment is of vital importance tolessen the changes in the mandibular angle area.Level of Evidence III. This journal requires that authorsassign a level of evidence to each article. For a fulldescription of these Evidence-Based Medicine ratings,please refer to the Table of Contents or the onlineInstructions to Authors