Post-printing processing and aging effects on Polyjet materials intended for the fabrication of advanced surgical simulators.

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.

Preclinical Application of Augmented Reality in Pediatric Craniofacial Surgery: An Accuracy Study.

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.

Assessment of a novel patient-specific 3D printed multi-material simulator for endoscopic sinus surgery.

Background: Three-dimensional (3D) printing is an emerging tool in the creation of anatomical models for surgical training. Its use in endoscopic sinus surgery (ESS) has been limited because of the difficulty in replicating the anatomical details. Aim: To describe the development of a patient-specific 3D printed multi-material simulator for use in ESS, and to validate it as a training tool among a group of residents and experts in ear-nose-throat (ENT) surgery. Methods: Advanced material jetting 3D printing technology was used to produce both soft tissues and bony structures of the simulator to increase anatomical realism and tactile feedback of the model. A total of 3 ENT residents and 9 ENT specialists were recruited to perform both non-destructive tasks and ESS steps on the model. The anatomical fidelity and the usefulness of the simulator in ESS training were evaluated through specific questionnaires. Results: The tasks were accomplished by 100% of participants and the survey showed overall high scores both for anatomy fidelity and usefulness in training. Dacryocystorhinostomy, medial antrostomy, and turbinectomy were rated as accurately replicable on the simulator by 75% of participants. Positive scores were obtained also for ethmoidectomy and DRAF procedures, while the replication of sphenoidotomy received neutral ratings by half of the participants. Conclusion: This study demonstrates that a 3D printed multi-material model of the sino-nasal anatomy can be generated with a high level of anatomical accuracy and haptic response. This technology has the potential to be useful in surgical training as an alternative or complementary tool to cadaveric dissection.

Innovative IntraValvular Impedance Sensing Applied to Biological Heart Valve Prostheses: Design and In Vitro Evaluation.

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.