Mixed Reality and Maxillofacial Surgery: An Interactive Twofold-Modality Application

Using custom-made physical cutting guides in maxillofacial surgery presents several drawbacks, mainly related to design, time, and costs. Even if the literature provides several Augmented Reality (AR) solutions, they mostly display cutting planes and static assistance for repositioning. This work proposes a Mixed Reality (MR) application, deployed on MicrosoftHoloLens2, to guide the surgeon in maxillofacial osteotomies and repositioning through intuitive and interactive digital content. A holographic panel allows selecting between the osteotomy and repositioning modes. With the first one, the cutting lines and the drilling points for the fixation plates are overlaid on the patient's skull. With the second one, three different kinds of feedback simultaneously guide the surgeon toward the correct final bone placement, step-by-step, according to the real-time fragment displacement. The MR app was tested by seven inexperienced subjects using a 3D-printed skull. Satisfactory results were obtained for maxillary osteotomy (i.e., less than 1.5 mm deviations) and relocation (i.e., the accuracy is about 0.7 mm and 0.6 degrees).