A Virtual Surgical Planning Algorithm for Delayed Maxillomandibular Reconstruction

Background: The absence of a tumor specimen, from which to obtain measurements at the time of delayed maxillo-mandible reconstruction, introduces degrees of uncertainty creating the need for substantial intraoperative guesswork by the surgeon. Using the virtual surgical planning(VSP) environment the size and shape of missing bony elements is determined, effectively "recreating the defect" in advance of the surgery. Three VSP techniques assist the reconstructive surgeon: patient-specific modeling, mirroring the normal contralateral side, and scaled normative data. To facilitate delayed reconstruction a hierarchical algorithm utilizing VSP techniques was developed. Methods: Delayed maxillo-mandible VSP reconstructions were identified from 2009-2016. Demographics, modeling techniques, and surgical characteristics were analyzed. Results: 16 reconstructions were performed for osteoradionecrosis with displacement(50.0%) or oncologic defects(37.5%). Most patients had prior surgery(81.3%) and preoperative radiation(81.3%); 4 had failed prior reconstructions. The following delayed VSP techniques were used: patient-specific modeling based on previous imaging(43.8%), mirroring normal contralateral anatomy(37.5%), and scaled normative data(18.8%). Normative and mirrored reconstructions were designed to restore normal anatomy; however, most patient-specific VSP designs(71.4%) required non-anatomic reconstructions to accommodate soft tissue limitations and to avoid the need for a second flap. One partial flap loss required a second free flap, and one total flap failure occurred. Hardware exposure was the most common minor complication, followed by infection, dehiscence, and sinus tract formation. Conclusion: VSP has inherent advantages in delayed reconstruction when compared to traditional flap shaping techniques. An algorithmic approach based on available imaging and remaining native anatomy enables accurate reconstructive planning followed by flap transfer without the need for intraoperative guesswork. * Both authors contributed equally to this manuscript and share first authorship. Presented at the American Associations of Plastic Surgeons, Austin, Texas 2017 Financial Disclosure: None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this manuscript. Acknowledgement: This research was funded in part through the NIH/NCI Cancer Center Support Grant P30 CA008748. Corresponding author: Dr. Evan Matros, 1275 York Avenue, New York NY 10065, Matrose@mskcc.org ©2019American Society of Plastic Surgeons

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