Introduction: In this research 3D models of oral maxillofacial (OMF) oncologic surgery specimens were created and registered onto preoperative CTs in their correct anatomical position. Histopathology information regarding gross section slices and margin status was included to create a comprehensive 3D model. This model was subsequently evaluated on the radiotherapy department for potential use in assisting with radiotherapy treatment planning. As part of this research, several 3D scanners were evaluated to determine which was most suited for human tissue scanning.
Results: Visual inclusion of histopathology information into a 3D model of an oncologic OMF specimen was achieved. Radiotherapy team deemd it a valuable addition in radiation treatment planning. The EinScan SP was evaluated as the most suitable 3D scanner for the purpose of human tissue scanning based on literature and testing against three other 3D scanners,

Introduction
Augmented Reality (AR) and Mixed Reality (MR) can be used for surgical navigation to execute the pre-operative plan. HoloMA is a novel AR/MR application which can guide the user to place surgical instruments on the planned location within the patient. In this pilot study, the AR/MR-guidance of HoloMA was used to place personalized canine acetabular roof implants on the pre-planned location on the iliac bone.

Methods
Dedicated tools to perform the AR/MR patient registration and surgical guidance were developed. An in silico patient registration test was conducted to assess if the available bony surface during the acetabular roof surgery was suitable to perform the patient registration accurately. Pilot tests to place implants using the AR/MR-guidance of HoloMA were conducted on phantoms, a cadaver and in an in vivo dog patient. The translational and angulation error between the planned and the post-operative implant positions were determined. The aim was to achieve implant placement with a maximum translational error of 4.0 mm and a maximum angulation error of 5.0° relative to the pre-operative plan.

Results
The in silico patient registration test demonstrated a mean translational error of 0.94 ± 0.23 mm and a mean angulation error of 2.49 ± 0.34°. In the phantom tests, implants (n=6) were placed with a mean translational error of 1.94 ± 0.79 mm. The mean angulation errors in this test were: 2.87 ± 1.81° (transversal plane), 1.72 ± 1.64° (dorsal plane) and 3.10 ± 2.52° (sagittal plane). Two of the implants of the phantom test and both implants of the cadaveric test (n=2) were positioned with a translational error exceeding 4.0 mm and/or angulation error exceeding 5.0° from the planned positions. No implants were placed using AR/MR-guidance in the in vivo dog patient test.

Conclusion
The results of the in silico patient registration test hold promise for the use of AR/MR-guidance in positioning personalized acetabular roof implants. However, the moderate outcomes observed in the phantom and cadaveric test suggest the need for further testing and improvements before deploying this AR/MR technology in a clinical setting.

Purpose: Patient-specific implants (PSIs) and surgical guides are widely used nowadays for the reconstruction of craniofacial defects. In this research, we quantitatively compared the realised position of craniofacial PSIs with the planned position and we calculated the difference between the realised osteotomy and the planned osteotomy if a resection preceded the reconstruction. Methods: We retrospectively included patients who received a craniofacial polyetheretherketone (PEEK) PSI in the LUMC between February 2019 and January 2021 and had a postoperative CT scan available. Postoperative CT scans were aligned with preoperative CT scans, followed by segmentation of the postoperative PSI position and skull, on which the realised osteotomy was defined by an inner and outer curve. Translation and rotation between the realised PSI position and planned PSI position were calculated as well as the surface distance between the realised osteotomy curves and the planned osteotomy. Results: 19 patients were included, regarding cranial (n = 11) and orbital (n = 8) implants. The translation vector length ranged from 0.5 mm to 6.7 mm and rotational deviation ranged from 0.9° to 17.4°, both being higher for orbital implants than for cranial implants (U = 3.00, p = .000, U = 15.0, p = .016). 12 patients were included in the osteotomy analysis. Mean distance between realised and planned osteotomy was 1.4 mm (SD 1.6) for outer curves and 0.5 mm (SD 1.7) for inner curves. Absolute mean distances over the two curves ranged from 0.6 mm (SD 0.5) to 4.1 mm (SD 2.6), accurately reproducing the planned osteotomy in most cases. Conclusion: In this study, there was a large variation in positioning accuracy for craniofacial PSIs. Cranial implants, being in good agreement with the planned PSI positions, were positioned with higher accuracy than orbital implants. In general, realised osteotomies were larger than planned. Better use and positioning of surgical guides could increase the PSI positioning accuracy. Clinical and aesthetical outcomes need to be included in future studies.