# Three-dimensional assessment of condylar head position in CBCT scans before and after orthognathic surgery

## TL;DR

This study uses 3D imaging to assess how condylar head position changes after orthognathic surgery and finds that surgeon handedness may affect the outcome.

## Contribution

The study introduces the use of Procrustes shape analysis to evaluate postoperative condylar head position and joint space deformation in orthognathic surgery.

## Key findings

- Postoperative condylar head position shifted caudally with significant cranial joint space widening on the right side.
- Procrustes analysis revealed measurable deformation in anterior and posterior TMJ compartments.
- Surgeon handedness appears to systematically influence condylar positioning during surgery.

## Abstract

Recent advances in orthognathic surgery—particularly the adoption of virtual 3D planning and patient-specific 3D-printed splints—have improved surgical precision, reduced operative time, and enhanced predictability of outcomes. Despite these developments, accurate intraoperative positioning of the mandibular condyle, especially the condylar head, during bilateral sagittal split osteotomy (BSSO), remains a major challenge. Although multiple techniques for condylar positioning have been proposed, their impact on postoperative condylar head position and joint space morphology has not been comprehensively assessed. This study aimed to evaluate postoperative changes in condylar head position and temporomandibular joint (TMJ) space using a Procrustes algorithm, and to investigate potential effects of surgeon handedness.

A retrospective cone beam computed tomography (CBCT) analysis was conducted on 40 patients (24 female, 16 male) who underwent orthognathic surgery. The cohort comprised 27 patients with Angle Class II and 13 with Angle Class III malocclusion. Eighteen patients underwent bimaxillary procedures, and 22 underwent monomaxillary osteotomies. Condylar position and joint space dimensions were measured, and Procrustes shape analysis was applied to quantify TMJ space deformation. Statistical tests assessed positional changes and correlations with skeletal class, displacement, and surgeon handedness.

Significant postoperative changes were observed, with a bilateral reduction in cranial distances, reflecting a more caudal condylar head position, and a significant widening of the cranial joint space on the right side. Procrustes analysis confirmed measurable deformation of anterior and posterior TMJ compartments. Condylar heads were frequently positioned dorsally during initial registration, and results suggest that surgeon handedness may systematically influence condylar positioning.

Postoperative condylar head position and TMJ space morphology are influenced by intraoperative handling, with surgeon handedness emerging as a potential contributor. Incorporating shape analysis methods such as Procrustes algorithms into future digital workflows may improve condylar positioning strategies and enhance surgical outcomes in BSSO.