Effect of Sagittal Maxillary Rotation on Inferior Scleral Exposure in Class III Maxillary Deficiency.

BACKGROUND

Inferior scleral exposure (ISE) is an important determinant of periorbital esthetics and overall facial harmony. While effects of linear maxillary movements are documented, influence of sagittal-plane maxillary rotational vectors on ISE remains insufficiently investigated.

PURPOSE: The purpose of this study was to measure the association between sagittal-plane maxillary rotational changes and ISE in subjects undergoing LeFort I osteotomy.

STUDY DESIGN, SETTING, AND SAMPLE: This retrospective cohort study was conducted at Medipol Mega University Hospital (Istanbul, Türkiye) and included subjects treated with LeFort I osteotomy for Class III maxillary deficiency between 2019 and 2022. Subjects were excluded if anterior vertical maxillary repositioning exceeded ±2.5 mm (impaction or inferior maxillary repositioning) or if they had craniofacial syndromes, prior midface surgery, or inadequate preoperative or postoperative photographic records.

PREDICTOR VARIABLE: Primary predictor was sagittal occlusal plane rotational change, measured in degrees (positive values indicating clockwise [CW] and negative values indicating counterclockwise [CCW] rotation).

MAIN OUTCOME VARIABLE: Primary outcome was the change in ISE between preoperative and postoperative assessments, evaluated using vertical distance from the pupil center to the lower eyelid margin and by pixel-based measurement of visible scleral area.

COVARIATES: Covariates included age and sex, sagittal maxillary advancement, and vertical maxillary repositioning.

STATISTICAL ANALYSIS: Preoperative and postoperative differences in ISE were assessed using paired t-tests. Between-group comparisons were performed using independent samples t-tests. Correlation analysis evaluated associations between sagittal rotation and changes in ISE. Statistical significance was set at P < .05.

RESULTS

The study included 42 subjects of whom 15 (35.7%) were male (mean age, 25 ± 7 years). Mean sagittal occlusal plane rotation was -2.2 ± 1.8° in CCW group and 3.2 ± 2.5° in CW group. ISE statistically significantly decreased postoperatively in CW group (P = .005-.041), whereas no statistically significant change was observed in CCW group. Sagittal rotational magnitude was not correlated with scleral change (r = -0.12 to -0.15; P = .5-.9). Vertical maxillary repositioning remained significantly associated with scleral reduction (P = .02), while sagittal rotation was not an independent predictor.

CONCLUSIONS

Although CW maxillary rotation was associated with reduced ISE in univariate analysis, vertical repositioning was a significant independent predictor. These findings emphasize importance of considering multiple vector components during virtual orthognathic surgical planning.