Impact of Preoperative Condylar Volume on Postoperative Displacement in Asymmetric Mandibular Setback Surgery: A Retrospective Cohort Study

Abstract

Background

Predicting postoperative condylar displacement remains a significant challenge in bilateral sagittal split ramus osteotomy (BSSO). The influence of preoperative condylar volume on such displacements is not well understood. This study aims to investigate the association between preoperative condylar and ramal volumetric parameters and postoperative condylar displacement following BSSO.

Methods

We conducted a single-center, retrospective cohort study of patients with skeletal Class III malocclusion who underwent BSSO between January 2018 and December 2023. The primary predictor variables were the volumetric parameters of the mandibular condyle and ramus, while the primary outcome was condylar displacement, quantified using cone-beam computed tomography (CBCT) scans at three time points: T0 (preoperative), T1 (immediate postoperative) and T2 (≥ 6 months postoperative). Covariates included age, sex and the magnitude of mandibular asymmetry.

Results

The study cohort comprised 37 subjects: 17 in the symmetric group (SG, mean age: 24.5 ± 6.3 years, 47.1% female) and 20 in the asymmetric group (AG, mean age: 27.4 ± 6.7 years, 55.0% female). No statistically significant differences in intraoperative or postoperative condylar movements were observed between the groups. Key correlations identified included a negative association between ramus volume and transverse displacement during surgical correction in AG (r = − 0.345, P = 0.029), as well as a negative correlation with roll rotation in SG (r = − 0.340, P = 0.049). Postoperatively, in the AG, larger condylar volume was associated with reduced vertical translation (r = − 0.381, P = 0.015), and a higher condyle–ramus index (CRI) was associated with less roll rotation (r = − 0.406, P = 0.009). No significant correlations were identified in SG during the postoperative phase.

Conclusions

This study identified an association between preoperative condylar/ramus volume and postoperative displacement patterns in asymmetric mandibular setback surgery, involving both translational and rotational components. However, the correlations observed were weak-to-moderate, indicating that volumetric parameters alone are not sufficient for reliable prediction at individual patient level. Further research employing larger, prospective cohorts is needed to validate these associations and to investigate whether specific anatomical subunits of the condyle demonstrate stronger correlations with postoperative stability.

Level of Evidence IV

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