Influence of vertical skeletal patterns on cancellous bone volume in the mandibular ramus relevant to sagittal split ramus osteotomy in skeletal class III patients: A cone-beam computed tomography analysis.

OBJECTIVES

To determine whether the vertical skeletal pattern influences cancellous bone volume and related ratios in sagittal split ramus osteotomy (SSRO)-relevant regions of the mandibular ramus in skeletal Class III patients, and to quantify covariate effects.

MATERIALS AND

METHODS

This single-center retrospective study included 112 patients (224 rami). Cone-beam computed tomography-based 3D segmentations quantified cancellous volume (ROI.S), cortical volume (ROI.C), total bone (TB), and ratios S:C and S:TB within a standardized ramal ROI. Because each patient contributed bilateral rami, within-patient correlation was accounted for using mixed-effects models (random intercept) for ROI.S, ROI.C, TB, ln-transform for S:C, and generalized estimating equations with an appropriate link were used for the bounded proportion S:TB (0-1). All models adjusted for sex, age, BMI, and side. Omnibus pattern effects were tested, with Bonferroni-adjusted pairwise comparisons reported when applicable. Intra- and inter-observer intraclass correlation coefficients (ICCs) were assessed in a 10-patient subset.

RESULTS

Vertical skeletal pattern was not associated with ROI.S (P = 0.17). Omnibus effects were observed for ROI.C (P = 0.04) and TB (P = 0.03), but no pairwise contrast remained significant after Bonferroni adjustment. The ratios showed no pattern effect (ln[S:C], P = 0.69; S:TB, P = 0.64). Males had larger ROI.S, ROI.C, and TB and a higher cancellous proportion.

CONCLUSIONS

Vertical skeletal pattern does not materially influence cancellous volume or its ratios within SSRO-relevant ramal ROIs, whereas sex shows consistent volumetric and proportional differences.

CLINICAL RELEVANCE: Patient-specific CBCT volumetry provides reproducible quantitative information beyond skeletal pattern classification and may aid SSRO planning by identifying patients with relatively limited cancellous support.