Refining orthognathic outcomes: 3D accuracy with patient-specific implants for facial asymmetry correction

This study evaluated the three-dimensional accuracy of maxillary and chin repositioning using patient-specific implants (PSIs) in non-syndromic patients with facial asymmetry. A retrospective cohort study was conducted at the University Hospital of Geneva between 2018 and 2023. Three-dimensional pre-operative planning and post-operative CT or CBCT scans of 21 patients with facial asymmetry were analyzed. Using 3D Slicer, images were imported and segmented, and the anterior surfaces of the maxilla and chin were extracted via Meshmixer. CloudCompare software calculated the distance between post-operative and pre-operative surface models using one million sample points. Boxplots visualized the distribution of signed Euclidean distances, and accuracy was assessed based on the proportion of values within ±2 mm. The mean difference between planned and actual post-operative surfaces was -0.9 mm for the maxilla and -0.5 mm for the chin. The proportion of values within the accuracy threshold was for the maxilla >90 % in 13 patients (62 %), 80-90 % in 5 patients (23.8 %), 50-80 % in 2 patients (9.5 %), and <50 % in 1 patient (4.8 %). For the chin, >90 % accuracy was observed in 7 patients (58.4 %), 50-80 % in 4 patients (33.3 %), and <50 % in 1 patient (8.3 %). These findings suggest that PSIs provide accurate maxillary and chin repositioning, with higher precision in maxillary repositioning. This study highlights the potential of PSIs to improve surgical outcomes in orthognathic procedures for facial asymmetry cases.