Three-Dimensional Cephalometric Analysis Based on Cone-Beam Computed Tomography of Hard and Soft Tissue Changes in Microgenia Patients Undergoing Genioplasty.

BACKGROUND

Advancement sliding genioplasty effectively corrects convex facial profiles. Characterizing hard and soft tissue changes is critical to optimizing surgical results. Cone-beam computed tomography-based three-dimensional cephalometric analysis is widely adopted to assess craniofacial surgical outcomes.

PURPOSE: The purpose of this study was to measure the association of hard and soft tissues changes in patients with microgenia undergoing advancement sliding genioplasty.

STUDY DESIGN, SAMPLE, AND

SETTING

Patients with microgenia were enrolled in this retrospective cohort study from January 2024 to January 2025 at the Department of Oral and Maxillofacial Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine. Those with maxillofacial trauma, secondary jaw deformity, prior chin plasty, or incomplete medical notes were excluded.

PREDICTOR VARIABLE: The predictor variable was microgenia severity, dichotomized based on facial convexity angle (FCA): ≤25 ° and >25 °. An FCA > 25 ° indicated more severe deformity.

MAIN OUTCOME VARIABLES: The primary outcome variable was soft tissue displacement relative to hard tissue displacement, expressed as the soft-to-hard tissue movement ratio.

COVARIATES: Covariates included age, sex, body mass index, mandibular plane angle, and soft tissue thickness.

ANALYSES: Descriptive statistics were calculated. Student's t-test or nonparametric tests were used for appropriate group comparisons. Intraclass correlation coefficients assessed intrarater reliability. Spearman's correlation evaluated variable associations. Multivariable linear regression models examined associations between microgenia severity and soft-to-hard tissue movement ratios. A two-tailed P value of < 0.05 was considered statistically significant.

RESULTS

The sample comprised 113 subjects with a mean age of 26.7 (4.4); 95 (84.01%) were female. Sagittal soft-to-hard tissue movement ratios ranged from 0.92 (0.13)-0.96 (0.09) to 0.63 (0.11)-0.70 (0.08) for patients with FCA ≤25 °, versus 0.98 (0.12)-1.03 (0.07) to 0.65 (0.07)-0.81 (0.11) in those with FCA>25 °. Intergroup comparison showed a statistically significant sagittal direction difference only at the menton [0.96 (0.09) vs 1.03 (0.07), P < .001]. Multivariable linear regression revealed microgenia severity had no independent association with soft-to-hard tissue movement ratios (all P > .05).

CONCLUSIONS AND RELEVANCE: Analysis demonstrated stable soft-to-hard tissue movement ratios in both sagittal and vertical chin movements. The findings provide quantitative evidence facilitating more accurate models for predicting postoperative soft tissue outcomes.