Application of computer-aided design/computer-aided manufacturing and mixed reality technologies in a novel...

Mandibular reconstruction following oral and maxillofacial tumor resection is essential for restoring occlusion and facial appearance. Conventional methods require intraoperative bending of plates, increasing surgical time and risking metal fatigue and plate fracture. Patient-specific implants (PSIs), created via preoperative computed tomography (CT) data and three-dimensional (3D) metal printing, have improved surgical accuracy and reduced operation times. In Japan, Cosmofix^® is the only PSI system available, but it lacks osteotomy guides, complicating precise bone cuts and screw insertion angles. To address these gaps, we developed custom-designed osteotomy guides, using computer-aided design (CAD)/computer-aided manufacturing (CAM) and in-house 3D printing, and incorporated mixed reality (MR) technology to enhance preoperative and intraoperative planning and accuracy. Preoperative CT and 3D reconstruction were performed, and the resection range and Cosmofix^® plate were designed in consultation with the engineer. The plate was equipped with claw-like projections to prevent displacement. Based on the plate design data, an osteotomy guide was created and manufactured using a 3D printer. Screw holes were designed for fixation. Using STL data, we created an application enabling multiple surgeons to visualize anatomical structures and resection margins in 3D during preoperative conferences and intraoperatively. A 22-year-old male patient with mandibular ameloblastoma underwent segmental resection and reconstruction using Cosmofix^®, a custom osteotomy guide, and MR technology. Preoperative virtual planning allowed precise design of the reconstruction plate and osteotomy guides, and MR applications enabled shared surgical understanding and verification of resection range, jaw positioning, and implant angles during surgery. Postoperative accuracy assessment showed that bone surface error within 1 mm was achieved in 94.1% (right) and 92.9% (left) of the surgical area. At 1 year postop, functional and aesthetic outcomes were favorable, with no plate or bone abnormalities or signs of recurrence; furthermore, the patient showed recovering nerve function. The combination of PSIs, custom osteotomy guides, and MR technology enabled accurate, efficient mandibular reconstruction. This approach improved surgical precision and resulted in excellent functional and cosmetic outcomes.