Background: Augmented reality (AR) allows the overlapping and integration of virtual information with the real environment. The camera of the AR device reads the object and integrates the virtual data. It has been widely applied to medical and surgical sciences in recent years and has the potential to enhance intraoperative navigation. Materials and methods: In this study, the authors aim to assess the accuracy of AR guidance when using the commercial HoloLens 2 head-mounted display (HMD) in pediatric craniofacial surgery. The Authors selected fronto-orbital remodeling (FOR) as the procedure to test (specifically, frontal osteotomy and nasal osteotomy were considered). Six people (three surgeons and three engineers) were recruited to perform the osteotomies on a 3D printed stereolithographic model under the guidance of AR. By means of calibrated CAD/CAM cutting guides with different grooves, the authors measured the accuracy of the osteotomies that were performed. We tested accuracy levels of ±1.5 mm, ±1 mm, and ±0.5 mm. Results: With the HoloLens 2, the majority of the individuals involved were able to successfully trace the trajectories of the frontal and nasal osteotomies with an accuracy level of ±1.5 mm. Additionally, 80% were able to achieve an accuracy level of ±1 mm when performing a nasal osteotomy, and 52% were able to achieve an accuracy level of ±1 mm when performing a frontal osteotomy, while 61% were able to achieve an accuracy level of ±0.5 mm when performing a nasal osteotomy, and 33% were able to achieve an accuracy level of ±0.5 mm when performing a frontal osteotomy. Conclusions: despite this being an in vitro study, the authors reported encouraging results for the prospective use of AR on actual patients.

Material Jetting (MJ) 3D printing technology is promising for the fabrication of highly realistic surgical simulators, however, the changes in the mechanical properties of MJ materials after post-printing treatments and over time remain quite unknown. In this study, we investigate the effect of different post-printing processes and aging on the mechanical properties of a white opaque and rigid MJ photopolymer, a white flexible MJ photopolymer and on a combination of them. Tensile and Shore hardness tests were conducted on homogeneous 3D-printed specimens: two different post-printing procedures for support removal (dry and water) and further surface treatment (with glycerol solution) were compared. The specimens were tested within 48 h from printing and after aging (30-180 days) in a controlled environment. All groups of specimens treated with different post-printing processes (dry, water, glycerol) exhibited a statistically significant difference in mechanical properties (i.e. elongation at break, elastic modulus, ultimate tensile strength). Particularly, the treatment with glycerol makes the flexible photopolymer more rigid, but then with aging the initial elongation of the material tends to be restored. For the rigid photopolymer, an increase in deformability was observed as a major effect of aging. The hardness tests on the printed specimens highlighted a significant overestimation of the Shore values declared by the manufacturer. The study findings are useful for guiding the material selection and post-printing processing techniques to manufacture realistic and durable models for surgical training.

Augmented Reality (AR) is an increasingly prominent technology with diverse applications across various surgical disciplines. This study aims to develop and assess the feasibility of a novel AR application intended to aid surgeons in the clinical assessment of temporomandibular joint (TMJ) alterations necessitating surgical intervention. The application employs a multi-modality tracking approach, combining both marker-less and marker-based tracking techniques to concurrently track the fixed portion of the joint and the movable mandible involved in TMJ. For the marker-based tracking both a planar marker with a binary QR-code pattern and a cuboid marker that contains a unique QR-code pattern on each face were tested and compared. The AR application was implemented for the HoloLens 2 head-mounted display and validated on a healthy volunteer performing the TMJ task, i.e. the opening and closing of the mouth. During the task, video recordings from the HoloLens cameras captured the horizontal and vertical excursions of the jaw movements (TMJ movements) using virtual markers anchored to the AR-displayed virtual anatomies. For validation, the video-recorded TMJ movements during AR viewing were compared with standard kinesiographic acquisitions. The findings demonstrated the consistency between the AR-derived trajectories and the kinesiography curves, especially when using the cubic Multi Target tracker to follow the moving mandible. Finally, the AR application was experienced on a patient and it was extremely useful for the surgeon to diagnose alterations in the normal kinematics of the TMJ. Future efforts should be addressed to minimize the bulkiness of the tracker and provide additional visual cues for surgeons.

This case report aims to describe novel steps in the digital design/manufacturing of facial prostheses for cancer patients with wide inoperable residual defects, with a focus on a case of a mid-facial defect. A facial scanner was used to make an impression of the post-surgical residual defect and to digitalize it. The daughter’s face scan was used for reconstructing the missing anatomy. Using 3D printing technologies, try-in prototypes were produced in silicone material. The substructure was laser melted. The final prosthesis was relined directly onto the patient’s defect. The prosthesis resulted in a very low weight and a high elasticity of the external margins. The laser-melted substructure ensured the necessary rigidity with minimum thickness.

Subclinical valve thrombosis in heart valve prostheses is characterized by the progressive reduction in leaflet motion detectable with advanced imaging diagnostics. However, without routine imaging surveillance, this subclinical thrombosis may be underdiagnosed. We recently proposed the novel concept of a sensorized heart valve prosthesis based on electrical impedance measurement (IntraValvular Impedance, IVI) using miniaturized electrodes embedded in the valve structure to generate a local electric field that is altered by the cyclic movement of the leaflets. In this study, we investigated the feasibility of the novel IVI-sensing concept applied to biological heart valves (BHVs). Three proof-of-concept prototypes of sensorized BHVs were assembled with different size, geometry and positioning of the electrodes to identify the optimal IVI-measurement configuration. Each prototype was tested in vitro on a hydrodynamic heart valve assessment platform. IVI signal was closely related to the electrodes’ positioning in the valve structure and showed greater sensitivity in the prototype with small electrodes embedded in the valve commissures. The novel concept of IVI sensing is feasible on BHVs and has great potential for monitoring the valve condition after implant, allowing for early detection of subclinical valve thrombosis and timely selection of an appropriate anticoagulation therapy.

Ossiculoplasty (OPL) aims to restore ossicular chain continuity to improve hearing in patients with conductive or mixed hearing loss, often performed during tympanoplasty. The current training methods, including cadaveric temporal bone models, face challenges such as limited availability, high costs, and biological risks, prompting the exploration of alternative models. This study introduces a novel training platform for OPL using 3D-printed temporal bones and incudes, including a magnified (3:1) model to enhance skill acquisition. Sixty medical students were divided into two groups: one trained on magnified models before transitioning to real-sized ones, and the other used only real-sized models. Training performance was quantitatively assessed using post-remodeling cone-beam CT imaging and mesh distance analysis. The results showed a significant improvement in performance for students with preliminary training on magnified models (87% acceptable results vs. 37%, p = 0.001). Qualitative feedback indicated higher confidence and skill ratings in the magnified model group. This study highlights the effectiveness of scalable, anatomically accurate synthetic models for complex surgical training. While further validation is required with experienced trainees and broader scenarios, the findings support the integration of 3D printing technologies into otologic education, offering a cost-effective, reproducible, and innovative approach to enhancing surgical preparedness.