Abstract
The lack of a standardized methodology complicates accuracy assessment in computer-assisted mandibular reconstruction. Existing landmark-based methods are susceptible to operator variability, while surface-based comparisons can mask local deviations. This study validates a novel, automated protocol, the Global Positioning Layout (GPL), to quantify the 3D discrepancy between the virtual surgical plan and the postoperative outcome, by comparing its performance and reliability against Methods A and B. A retrospective cohort of 17 patients was analysed, with three operators performing all measurements on two occasions. The GPL method demonstrated complete reproducibility, with no inter- or intra-operator variability, providing a detailed, spatially-oriented assessment of deviations. In contrast, the landmark-based method showed poor reproducibility and systematic bias and was often inapplicable due to the absence of landmarks after resection. The surface-based method, while objective for its mean error metric, was operator-dependent for initial alignment and its non-directional output masked significant localized deviations. This study validates GPL as a robust and fully reproducible tool that overcomes the critical limitations of established techniques. The GPL method provides a strong foundation for a standardized protocol, essential for the reliable comparison of surgical outcomes, refinement of surgical techniques, and improvement of long-term patient outcomes.
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References
Rodby, K. A. et al. Advances in oncologic head and neck reconstruction: Systematic review and future considerations of virtual surgical planning and computer aided design/computer aided modeling. Journal of Plastic, Reconstructive and Aesthetic Surgery 67 1171–1185 Preprint at https://doi.org/10.1016/j.bjps.2014.04.038 (2014).
Seruya, M., Fisher, M. & Rodriguez, E. D. Computer-Assisted versus conventional free fibula flap technique for craniofacial reconstruction. Plast. Reconstr. Surg. 132, 1219–1228 (2013).
van Baar, G. J. C., Forouzanfar, T., Liberton, N. P. T. J., Winters, H. A. H. & Leusink, F. K. J. Accuracy of computer-assisted surgery in mandibular reconstruction: A systematic review. Oral Oncol. 84, 52–60 (2018).
Mascha, F. et al. Accuracy of computer-assisted mandibular reconstructions using patient-specific implants in combination with CAD/CAM fabricated transfer keys. J. Cranio-Maxillofacial Surg. 45, 1884–1897 (2017).
van Baar, G. J. C., Liberton, N. P. T. J., Forouzanfar, T., Winters, H. A. H. & Leusink, F. K. J. Accuracy of computer-assisted surgery in mandibular reconstruction: A postoperative evaluation guideline. Oral Oncol. 88, 1–8 (2019).
Zhang, L. et al. Evaluation of computer-assisted mandibular reconstruction with vascularized fibular flap compared to conventional surgery. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. 121, 139–148 (2016).
Metzler, P., Geiger, E. J., Alcon, A., Ma, X. & Steinbacher, D. M. Three-Dimensional virtual surgery accuracy for free fibula mandibular reconstruction: planned versus actual results. J. Oral Maxillofac. Surg. 72, 2601–2612 (2014).
Wilde, F. et al. Multicenter study on the use of patient-specific CAD/CAM reconstruction plates for mandibular reconstruction. Int. J. Comput. Assist. Radiol. Surg. 10, 2035–2051 (2015).
Chernohorskyi, D. M., Chepurnyi, Y. V., Vasiliev, O. S., Voller, M. V. & Kopchak, A. V. Evaluation of the accuracy of surgical reconstruction of mandibular defects when using navigation templates and patient-specific titanium implants. J. Educ. Health Sport. 11, 117–132 (2021).
El-Mahallawy, Y., Abdelrahman, H. H. & Al-Mahalawy, H. Accuracy of virtual surgical planning in mandibular reconstruction: application of a standard and reliable postoperative evaluation methodology. BMC Oral Health 23, 119 (2023).
Annino, D. J. et al. Virtual planning and 3D-printed guides for mandibular reconstruction: factors impacting accuracy. Laryngoscope Investig Otolaryngol. 7, 1798–1807 (2022).
Zavattero, E. et al. Accuracy of fibula reconstruction using Patient-Specific Cad/Cam plates: A multicenter study on 47 patients. Laryngoscope 131, E2169–E2175 (2021).
Goormans, F. et al. Accuracy of computer-assisted mandibular reconstructions with free fibula flap: results of a single-center series. Oral Oncol. 97, 69–75 (2019).
Bao, T. et al. Reliabilities of three methods used to evaluate computer-assisted mandibular reconstructions using free fibula flaps. Heliyon 10, e37725 (2024).
Zhou, Z., Zhao, H., Zhang, S., Zheng, J. & Yang, C. Evaluation of accuracy and sensory outcomes of mandibular reconstruction using computer-assisted surgical simulation. J. Cranio-Maxillofacial Surg. 47, 6–14 (2019).
Tarsitano, A. et al. Accuracy of CAD/CAM mandibular reconstruction: A three-dimensional, fully virtual outcome evaluation method. J. Cranio-Maxillofacial Surg. 46, 1121–1125 (2018).
Bevini, M., Vitali, F., Ceccariglia, F., Badiali, G. & Tarsitano, A. Accuracy evaluation of an alternative approach for a CAD-AM mandibular reconstruction with a fibular free flap via a novel hybrid Roto-Translational and surface comparison analysis. J Clin. Med 12, 1938 (2023).
Vargiu, E. et al. Methodological Approach to Accuracy Assessment in CAD-CAM Mandibular Reconstruction. Preprint at https://doi.org/10.32388/CDHISR.2 (2025).
Bedogni, A. et al. Safety of boneless reconstruction of the mandible with a CAD/CAM designed titanium device: the replica cohort study. Oral Oncol 112, 105073 (2021).
Boyd, J. B., Gullane, P. J., Rotstein, L. E., Brown, D. H. & Irish, J. C. Classification of mandibular defects. Plast. Reconstr. Surg. 92, 1266–1275 (1993).
Roser, S. M. et al. The accuracy of virtual surgical planning in free fibula mandibular reconstruction: comparison of planned and final results. J. Oral Maxillofac. Surg. 68, 2824–2832 (2010).
Schepers, R. H. et al. Accuracy of fibula reconstruction using patient-specific CAD/CAM reconstruction plates and dental implants: A new modality for functional reconstruction of mandibular defects. J. Cranio-Maxillofacial Surg. 43, 649–657 (2015).
Hanken, H. et al. Virtual planning of complex head and neck reconstruction results in satisfactory match between real outcomes and virtual models. Clin. Oral Investig. 19, 647–656 (2015).
Lim, S. H., Kim, M. K. & Kang, S. H. Precision of fibula positioning guide in mandibular reconstruction with a fibula graft. Head Face Med. 12, 7 (2016).
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Conception, V.E., T.L., Bet.G., M.R., B.A. Methodology, V.E., Bed.G., M.R., B.A. Acquisition of data: M.G., T.L.,F.P., S.G., Bet.G. Analysis of data: V.E., Bed.G., M.R, B.A. Writing and original draft preparation: V.E., B.A.,M.R. Revision and critical editing: T.L., Bet.G., M.G.,F.P., S.G, Bed.G., M.R. All authors have read and approved the submitted version of the manuscript. All Authors have agreed both to be personally accountable for the author’s own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature.
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The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethical Committee of the University Hospital of Padova (protocol number 24435/AOP1814 April 2019); all patients gave their written informed consent.”
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Vargiu, E., Tognin, L., Bettini, G. et al. Automated Global Positioning Layout (GPL) for accuracy assessment in CAD-CAM mandibular reconstruction – Method validation. Sci Rep (2026). https://doi.org/10.1038/s41598-025-30516-1
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DOI: https://doi.org/10.1038/s41598-025-30516-1
