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Facial Transplantation in Six Degrees of Freedom: The Role of Computer Assisted Design and Manufacturing
Philip S. Brazio, MD, Amir H. Dorafshar, MD, Branko Bojovic, MD, Michael R. Christy, MD, Daniel E. Borsuk, MD, Emile N. Brown, MD, Eduardo D. Rodriguez, MD, DDS.
University of Maryland, Baltimore, MD, USA.
Full facial osteomyocutaneous transplantation requires the correct 3-Dimensional spatial alignment of osseous structures to a new cranial base. Traditional cephalometry addresses only 2-Dimensional movements. Novel methods using computer assisted design and manufacturing (CAD/CAM) can be devised to reliably and reproducibly plan and execute the proper alignment of the facial skeleton onto the new cranial base for optimum form and function.
Three-dimensional modeling software was used to plan Le Fort III-based facial segment allotransplantation in five cadaver pairs and one clinical pair using computed tomographic data. Donor and recipient virtual surgically planned osteotomies were performed and the donor facial osteomyocutaneous flap was superimposed onto the recipient cranial base. The virtually planned surgery was then translated to the cadaver using osteotomy cutting guides and surgical navigation. Computed tomographic images post transplantation were completed. The 3-Dimensional differences between preoperative donor and recipient, to planned and actual craniofacial skeletons following transplantation were compared.
CAD/CAM and intra-operative navigation enabled precise planning and execution of Le Fort III osteotomies. Three-dimensional visualization allowed quantitative analysis of midfacial alignment along all three translational axes (vertical, horizontal, and anteroposterior; Figure 1) and all three rotational axes (pitch, yaw, and roll; Figure 2). Postoperative CT results were quantitatively similar to the planned transplantation in all six degrees of freedom, without significant differences (p>0.05 for all). Both projected transplants and postoperative results tended to fall between donor and recipient values.
The nascent field of face transplantation requires maximum precision in planning and execution of midfacial osteotomies. We demonstrate a novel application of CAD/CAM that allows precise osteotomies to be performed according to a preplanned virtual surgical plan. Visualization of these movements in all six degrees of freedom assists the surgeon with craniofacial alignment in cases of complex facial transplantation where the bony segments have to be reattached to a new cranial base in 3 Dimensions.
Figure 1. Measurement of translation along the (a) anteroposterior axis using SNA angle; (b) vertical axis using nasion-ANS distance; and (c) horizontal axis using distances from first maxillary molars to cranial base midline plane.
Figure 2. Measurement of rotation about the (a) anteroposterior axis using distances from zygomatic-frontal suture to first maxillary molar (roll); (b) vertical axis using angular deviation of maxillary midline from cranial base midline plane (yaw); and (c) horizontal axis using SN-occlusal plane angle (pitch).
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