Influence of bone-cut position in intraoral vertical ramus osteotomy on skeletal stability after mandibular setback

Background/purposePostoperative skeletal stability is associated with osteotomy design of orthognathic surgery. The purpose of this study was to investigate osteotomy site-related factors of intraoral vertical ramus osteotomy (IVRO) related to skeletal relapse in a 2-year postoperative follow-up.Materials and methodsTwenty-seven patients with mandibular prognathism underwent surgical mandibular setback with IVRO. Cephalometric radiographs of the patients were collected after completing preoperative orthodontic treatment (T1), at the stage immediately after surgery (T2), and in the 2-year postoperative follow-up (T3). Pir was located at the posterior most and inferior most ramus point. Io was the inferior most osteotomy point of the mandible. Relapse was defined as forward movement of menton (Me) in the 2-year follow-up. Hierarchical modeling analyses were used to assess changes in the variables, including the amount of postoperative relapse (MeT32), the quantity of surgical setback (MeT21), the available setback horizontal distance (Pir–Io), and the available setback ratio (MeT21/Pir–Io).ResultsThe mean setback of Me was 12.6 mm, and the mean relapse was 0.9 mm (7.1% = 0.9/12.6). In the 1-by-1 and 1-by-2 models, there were no significant differences between the relapse and other variables. However, we found a significant difference in the 1-by-3 model. The MeT21 and MeT21/Pir–Io were significant factors in postoperative relapse.ConclusionWe found that multiple factors contributed to postoperative relapse of IVRO. Our study also confirmed the 2-year stability of IVRO in treating mandibular prognathism.