Mandibular positioning using patient-specific guides and osteosynthesis implants in bimaxillary orthognathic surgery with maxilla-first approach. A 3D-analysis.

The aim of this study was to evaluate the accuracy of a fully 3D planned digital workflow for bimaxillary osteotomies, utilizing patient-specific osteotomy and drill guides (PSDOG) and osteosynthesis implants (PSOI), within a maxilla-first approach. Emphasis was placed on the accuracy of guided mandibular positioning. This retrospective study included 30 patients undergoing bimaxillary orthognathic surgery [bimaxillary PSDOG/PSOI (Group 1; n = 11) versus maxillary PSDOG/PSOI (Group 2; n = 19)]. 3D CT datasets were used for accuracy assessment. Primary outcome parameter was the accuracy of the intraoperative mandibular transfer evaluated on cephalometric landmarks. Secondary outcome parameter was the 3D accuracy of mandibular positioning. Cephalometric analysis revealed significant vertical undercorrections and lateral deviations in the positioning of proximal mandibular segments (adj. p < 0.05). 3D analysis revealed a trend towards lower maximal deviations at the left ascending ramus in Group 1 (p = 0.058). Moderate positional accuracy was observed, with the largest vector deviations occurring in the latero-inferior-anterior direction. Iatrogenic injuries and bad splits were lower in Group 1 (p ≥ 0.52). Duration of surgery did not differ significantly between groups (p = 0.21). Fully guided and patient-specific orthognathic procedures enable precise and reproducible mandibular repositioning and may contribute to a reduction in intraoperative complication rates. However, control of the proximal segments, particularly condylar positioning, remains limited.