Changes in Facial Soft Tissues After Mandibular Angle Ostectomy Based on 3-Dimensional Measurement: A Clinical Study.

Purpose: A limited number of clinical studies have focused on the changing trends of facial soft tissue after mandibular angle ostectomy. We conducted this study to investigate the changes in facial muscles and facial soft tissue appearance before and after mandibular angle ostectomy.
Material and Methods: A single-center retrospective cohort study was conducted on female patients admitted to our hospital for mandibular angle ostectomy between 2019 and 2020. The primary predictor variable was time (preoperative vs 6 months postoperative). The primary outcome variables were surface area and total volume of the manually delineated region of interest (ROI) for the masseter and temporalis muscles. We utilized computed tomography data to reconstruct 3-dimensional models to delineate muscle ROI and then measure them computationally. Secondary outcome variables were indicators of mandible appearance in soft tissue including bilateral mandibular angle distance, mandibular ramus height, and mandibular angle value. Age, preoperative body mass index, and ostectomy volume were chosen as covariates for correlation analysis with outcome variables. Paired t tests and Pearson correlation analysis were conducted, and P values < .05 were considered statistically significant.
Results: A total of 29 female patients (mean age, 26 years; range, 18 to 37 years) who underwent mandibular angle ostectomy in our hospital were included. The surface area and total volume of the masseter muscle ROI were reduced by 2,541.2 ± 1,925.0 mm ² (12.8%; P < .05) and 16,242.4 ± 12,646.8 mm ³ (18.4%; P < .05), respectively, 6 months after surgery. In contrast, the surface area and total volume of the temporalis muscle ROI increased by 6,081.6 ± 6,169.4 mm ² (12.0%; P < .05) and 19,273.3 ± 21,666.2 mm ³ (10.7%; P < .05), respectively. The ostectomy volume showed a correlation coefficient of 0.59 with postoperative masseter ROI change (P < .05).
Conclusion: We observed statistically significant levels of atrophy of the masseter muscle ROI and expansion of the temporalis muscle ROI 6 months after mandibular angle ostectomy, which may account for appearance changes after surgery. Besides, ostectomy volume positively correlates with postoperative masseter ROI changes. In summary, our study provided empirical evidence illustrating soft tissue alterations in patients who have undergone mandibular angle ostectomy.
(Copyright © 2022 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)