Remodeling of the Temporomandibular Joint After Mandibular Setback Surgery: A 3D Cephalometric Analysis

Background: Condylar adaptations following orthognathic surgery remain an area of interest. Prior studies do not use 3-dimensional imaging modalities and lack standardization in the choice of osteotomy and movement when assessing condylar changes. Purpose: The purpose of this study was to use 3-dimensional cephalometry to measure the association between osteotomy type (sagittal split osteotomy [SSO] vs vertical ramus osteotomy [VRO]) and changes in condylar volume and position. Study Design, Setting, and Sample: This is a retrospective cohort study from January 2021 through December 2022 of patients at Bellevue Hospital in New York City, New York who were treated with either SSO or VRO for the correction of Class III skeletal malocclusion. Predictor/Exposure/Independent Variable: The primary predictor was the type of mandibular osteotomy, sagittal split osteotomy, and vertical ramus osteotomy. Main Outcome Variables: The primary outcomes were changes in condylar volume (change measured in mm(3)) and relative position (anterior-posterior change utilizing the Pullinger and Hollinder method). Covariates: Covariates included patient age, sex, setback magnitude, temporomandibular joint symptoms, and fixation method for SSO patients. Analyses: Univariate comparisons were performed between independent variables and study outcomes. Volume changes were compared within each predictor using paired t-tests. Position changes were compared within each predictor using chi(2) tests. If there were multiple significant univariate predictors, multiple regression models were created to predict volume and position changes. AP < .05 value was considered statistically significant. Results: The final sample comprised 30 condyles derived from 30 subjects. Mean age was 22.7 years (SD = 5.7) and mean setback was 3.9 mm (SD = 0.9). Twenty two condyles (73.3%) were subject to SSO with fixation, while the remaining 8 (26.7%) condyles were subject to intraoral VRO without fixation. When compared to VRO, condyles manipulated with SSO had greater volume loss (177.2 vs 60.9 mm3; P = .03) and positional change (68.2 vs 12.5%; P < .01). Self-reported measures of postoperative pain, internal derangement, and myofascial symptoms were not significantly associated with either volume or positional changes. Conclusions and Relevance: The SSO resulted in greater postoperative condylar volume loss and positional changes. These volume and positional changes were not correlated with self-reported temporo-mandibular disorder symptoms.(c) 2023 American Association of Oral and Maxillofacial Surgeons