Methods for medical applications

This article presents a methodology for the design and production of custom prostheses for complex surgical interventions on long bones due to oncological surgical treatment. This type of intervention considers the complete or partial removal of bone tissue that might be affected by bone tumors. In this scenario it is important to limit the loss of functionality of the patients' joints. Accordingly, it is important to salvage, whenever possible, the original articulation surfaces of the joints; nevertheless, a complete evaluation of the tumor extension and of the state of bone tissue might be difficult to be performed in the preparation phase. The article presents an approach for geometrical modelling of a modular prosthesis for long bones, that leaves the surgeon free to tailor the resection according to their feedback in the operating theatre. Specifically, the devised methodology allows to salvage part of the original bone by switching modules of the prosthesis. The dissertation is tackled from a technical perspective, taking into account the constraints and key features that need to be considered in the design and production of a long bone prosthesis via additive manufacturing technologies. The methodology is presented with reference to a complex custom prosthesis design that was carried out with the support of T3Ddy's - Personalized pediatrics by inTegrating 3D aDvanced technologies research laboratory.

Keywords: Additive Manufacturing , Custom prosthesis , Design for Additive Manufacturing

Patients with spinal problems have difficulty when performing activities of daily living due to weakness or paralysis in the joints and muscular system, and this is a serious problem for people of all ages because it negatively affects their socio, physio, and economic lives. Traditional orthopedic corsets are a valuable support for these patients because these devices enable them to perform specific activities that require motor control, such as sitting, walking and other physical activities. However, they are often bulky, poorly ventilated and manufactured with non-biocompatible materials. This research focuses on the design and manufacturing of bespoke orthopedic corsets through a new organic bioplastic compound, optimizing the aspects of functionality, light weight, and small footprint. The developed orthosis offers design flexibility and improved porosity control, performing the functions of an exoskeleton, assisting patients with spinal problems who cannot be operated on because they have high risks during surgery, e.g., herniated disc, osteoporosis, injury, osteoarthritis, etc. It allows pain relief and the continuation of even the simplest activities of daily living making patients more independent. The most suitable materials, such as polymers and their composites, were evaluated to manufacture a customized and biodegradable orthosis. Future goals include automating the process of designing and printing the customized orthosis from a real-time scan of the patient's torso.

Keywords: Custom-made orthosis , Daily living activities , Orthopedic corset , Rehabilitation field , Wearable device

In the realm of cardiac health research, accurate fluid dynamics simulations are vital for comprehending the heart function and diagnosing conditions. Central to these simulations is the precision of ventricular wall meshes used to model heart geometry. However, segmenting the wetted surface, particularly in the right ventricle (RV) with its significantly thinner parietal thickness compared to the left ventricle, presents challenges. This study focuses on qualitatively evaluating an automated reconstruction model for the RV's outer wall using Radial Basis function (RBF) morphing. Two procedural criteria were compared, a random selection of control points and a curvature-based approach, which differ in terms of the identification of the control points of the RBF function. From these considerations, it emerges that a controlled use of the RBF function on the basis of the curvatures guarantees the greater controllability of the shape evolutions of the parietal structure of the RV, but it is more sensitive to any anomalies in the distribution of the vertices, as can be seen from the number of outliers, and its controllability is a function of the percentage of points chosen, exerting a greater impact on the required computational capacity. The definition of a strategic criterion for the selection of control points could represent a crucial aspect in the definition of an automatic reconstruction procedure of anatomical elements, which guarantees a morphological variability in line with the need to expand the pathological sample to be used for statistical formulations in the clinical field.

Keywords: morphing , radial basis functions , right ventricle

Background: Joint-sparing resection of juxta-articular knee tumors is challenging. With the development of 3D printing technology, custom-made cutting guides were introduced with the aim to improve the accuracy of tumor resection margins and to shape the allograft for adequate matching in biological reconstruction. Materials and Methods: Between December 2017 and July 2023, 13 patients underwent joint-sparing juxta-articular resection of the knee for a primary bone tumor at our institution. Resection was performed using a custom-made 3D-printed titanium alloy cutting guide and reconstruction was performed using a custom-shaped allograft. The mean follow up was 50 months (min 14–max 81). The study of cutting accuracy was performed by digital examination of CT images of the resection specimen in eight patients. Results: The average cutting error was 2.3 mm. Surgical margins were wide in all patients. Four patients developed postoperative complications that led to the removal of the allograft in one case. The average functional result according to the Musculoskeletal Tumor Society Score was 26 (min 14–max 30), and according to the Oxford Knee Score it was 44 (min 22–max 48). Conclusions: Custom-made titanium cutting guides resulted effective in improving the accuracy of joint-sparing juxta-articular resection of the knee and allograft matching.

Keywords: 3D printing , bone tumors , custom made , cutting guides , juxta-articular tumors

Conducting thoracoscopic surgery necessitates a high level of skill and specialized training. In addition to practicing on actual patients, surgeons utilize various safer training methods. A widely used training apparatus is the laparoscopic box, which contains multiple compartments fitted with training modules to replicate diverse surgical scenarios accurately. Unfortunately, the cost of these devices can be prohibitively high, making it challenging for individual students to acquire their own. Virtual Reality has emerged as a promising solution, especially due to the decreasing costs of VR equipment, which makes it more accessible. This study details our progress in enhancing training for lung surgeries by leveraging cost-effective VR technologies with head-mounted displays. In particular, simulations of thoracoscopic surgery scenarios within a VR environment have been developed, aiming to create training exercises that serve as an initial step before advancing to laparoscopic simulation boxes and, ultimately, actual surgical procedures on patients. For reproducing the behaviour of the soft lung tissues, we used a recent version of the Extended Position-Based Dynamics (XPBD) model, which solves some of the known problems encountered in the traditional PBD system, thereby enhancing the realism of the simulation.

Keywords: Position-based Dynamics , Training , Virtual Reality

Markerless systems and inertial sensors, such as inertial measurement units, offer significant advantages over traditional marker-based methods by eliminating the need for laboratory conditions or markers placement. Virtual reality is an innovative technology used in rehabilitation, recently investigated for obtaining kinematic motion data. This research aims to validate a markerless system using a MediaPipe-based algorithm to reconstruct joint kinematics during exercises with the Nirvana virtual reality rehabilitation system. In the first phase, the markerless system was evaluated against the Xsens inertial measurement unit system, analyzing knee, hip, elbow and shoulder movements of 7 healthy participants at the Politecnico di Milano. The MediaPipe algorithm showed high performance in tracking lower limb movements but was less accurate for upper limbs, as indicated by RMSE and %RMSE values. However, it accurately replicated the time course of all angles based on ICC and Spearman's coefficient, suggesting virtual reality's feasibility in rehabilitation and movement analysis. In the second phase, a pilot study was carried out at the Fondazione TOG on 2 participants with left hemiparesis to assess the efficacy of the system in a pathological context. The results provide a basis for evaluating the potential clinical applicability of the system.

Keywords: Inertial Measurement Units , Markerless , MediaPipe algorithm , Rehabilitation , Virtual reality

Objective: The paper proposes a non-invasive original methodology to directly and automatically identify the spine line from the external position of vertebral apophyses, which are key anatomical landmarks. Methods: Apophyses are detected directly on discrete high-density geometric models of human backs acquired by a 3D scanner. The methodology is inspired by the posturologist's approach that detects the spine line through the identification, by manual palpation, of the spinal apophyses. For this purpose, an appropriate shape index is used to identify vertebral positions. The shape index estimates the local differential geometric properties of the back surface. This index is very discriminating in locating both pronounced and blurred apophyses. To validate the method, the research involved the analysis of 21 healthy human backs acquired in both standing and asymmetric postures. For each of them, a skilled operator detected the spinal apophyses by tactile investigation and located them through cutaneous marking. Markers have been used as the reference for spinal apophyses' positions. Results: A comparison of the proposed approach with state-of-the-art methods has been conducted. This study evidences the high accuracy of the methodology proposed here and the capability to recognize also blurred apophyses. Conclusion: The method automatically performs the spine line identification and accurately locates apophyses along both vertical and coronal directions. Significance: The proposed inexpensive and easy-to-use approach significantly advances over other non-invasive methods. Its ability to detect the apophyses' location potentially offers new capabilities in detecting, diagnosing, and monitoring spinal disorders.

Keywords: optical methods in medicine , shape index , Spinal apophyses recognition , spine line , symmetry line

Functional evaluation plays an important role in determining suitable training programs for elite athletes. For athletes with Intellectual Impairment, it may represent an even more powerful tool as it allows to obtain quantitative feedbacks (when qualitative ones are hard to collect). This study presents practical examples in the context of strength assessment tests carried out in the functional evaluation project of the Italian Sport Federation for athletes with Intellectual Impairment (FISDIR). In particular, a useful customized tool for the assessment of explosive strength in sprinters, based on biomechanical indices, is presented. The proposed approach starts with the definition of key biomechanical parameters in terms of spatiotemporal, kinematic, kinetics, energetic and joint angles related to each main phase of the test. According to the literature and technical recommendations, reference target values for each parameter are defined and normalized. In addition, a quick graphical visualization was designed. Finally, two synthetic indices related to the performance and execution are developed. Practical implications in squat jump test are presented. The proposed methodology represents a useful customized tool for improving training in athletes with Intellectual Impairment.

Keywords: biomechanics , Functional evaluation , intellectual impairment , strength assessment

—Mixed Reality (MR) is proven in the literature to support precise spatial dental drill positioning by superimposing 3D widgets. Despite this, the related knowledge about widget's visual design and interactive user feedback is still limited. Therefore, this study is contributed to by co-designed MR drill tool positioning widgets with two expert dentists and three MR experts. The results of co-design are two static widgets (SWs): a simple entry point, a target axis, and two dynamic widgets (DWs), variants of dynamic error visualization with and without a target axis (DWTA and DWEP). We evaluated the co-designed widgets in a virtual reality simulation supported by a realistic setup with a tracked phantom patient, a virtual magnifying loupe, and a dentist's foot pedal. The user study involved 35 dentists with various backgrounds and years of experience. The findings demonstrated significant results; DWs outperform SWs in positional and rotational precision, especially with younger generations and subjects with gaming experiences. The user preference remains for DWs (19) instead of SWs (16). However, findings indicated that the precision positively correlates with the time trade-off. The post-experience questionnaire (NASA-TLX) showed that DWs increase mental and physical demand, effort, and frustration more than SWs. Comparisons between DWEP and DWTA show that the DW's complexity level influences time, physical and mental demands. The DWs are extensible to diverse medical and industrial scenarios that demand precision.

Keywords: co-design , dentistry , Dynamic widgets , mixed reality , precise tool positioning , usability testing

The incorporation of immersive technologies such as virtual reality into medical settings, particularly in the context of preoperative planning, has the potential to enhance the accuracy and efficiency of surgical procedures. This preliminary study aims to develop an application specifically focused on the surgical intervention of tibial osteotomy. More precisely, this research integrates virtual reality to enhance preoperative planning, affording surgeons direct interaction with patient anatomical structures within a virtual environment, thereby facilitating precise decision-making. The manipulation of virtual three-dimensional reconstructions derived from medical imaging modalities such as computed tomography and magnetic resonance imaging is achievable through the integration of advanced modelling software and a virtual environment mimicking the operation room. This enables user navigation, object interaction, and outcome preservation. The study provides a detailed account of the design and implementation of a virtual reality application to simulate the surgical planning phase. This enables surgeons to visualise and execute the procedure intuitively. Despite promising progress toward virtual planning, further enhancements are necessary to fully supplant conventional methods. This includes the emulation of soft tissue interactions and the refinement of graft design processes within the virtual environment. Notwithstanding these challenges, this investigation demonstrates the potential of virtual reality to revolutionise preoperative planning paradigms, heralding a new era of immersive and efficacious surgical practices.

Keywords: Paediatric Orthopaedics , Surgical Planning , Virtual Reality

Purpose: This study aims to integrate design methods and additive manufacturing with the use of a thermoplastic elastomer certified for medical use and reverse engineering towards a new concept of a customized buttress model with optimized features for the reconstruction of the osteo-dural opening after endoscopic endonasal transtuberculum-transplanum approach. Design/methodology/approach: Additive manufacturing allows making of cost-effective and useable devices with tailored properties for biomedical applications. The endoscopic endonasal approach to the suprasellar area enables the management of different intradural tumours, and the craniectomy at the skull base is generally wide and irregular. Defining an optimal strategy for osteodural defect closure at the preoperative stage represents a significant challenge. Findings: Using the results obtained from a computed tomography analysis, skull base defects were designed to plan the surgical approach. Several concepts of customized buttress models were first built up, initially focusing on thin, flexible edges characterized by different thicknesses. Finite element analyses and design optimization allowed us to achieve the optimal design solution with improved compliance/flexibility for easy intranasal manoeuvrability, maintaining an adequate mechanical stability. As the thickness of the edges decreased, an increase of strain energy values was found (i.e. 1.2 mJ – Model A, 1.7 mJ – Model B, 2.3 mJ – Model C, 4.3 mJ – Model D). However, a further optimization (Model E) led to a significant increase of the compliance (strain energy of 14.1 mJ). Originality/value: The results obtained from clinical evaluations demonstrated the feasibility of the proposed technical solutions, improving surgery effectiveness.

Keywords: Design for additive manufacturing , Endoscopic endonasal approach , Finite element analysis , Mechanical measurements , Pituitary surgery , Reverse engineering

Recent technological advances in the field of Additive Manufacturing (AM) and the increasing need in Regenerative Medicine (RM) for devices that better and better mimic native tissue architecture are showing limitations in the current scaffolds fabrication techniques. A switch from the typical layer-by-layer approach is needed to achieve precise control on fibres orientation and pores dimension and morphology. In this work a new AM apparatus, the RAVEN (Robot-Assisted Volumetric ExtrusioN) system, is presented. RAVEN is based on a 7-DOF robotic arm and an extruder and allows for volumetric extrusion of polymeric filaments. The development process, namely the robotic motion optimisation, the optimisation towards small-scale trajectories, the custom-made hardware/software interfaces, and the different printing capabilities are hereby presented. The successful results are promising towards future advanced applications in which the ability of the robot to change its configuration while printing will be crucial.

Keywords: Design for additive manufacturing , measurements , regenerative medicine , robot-assisted volumetric extrusion , robotic arm , small-scale manufacturing

Meniscal tears may adversely impair knee function and biomechanics, with effects varying based on tear type and location. There are several methods for studying meniscal injuries, including human cadavers, and computational models, such as Finite Element Analysis (FEA). Previous studies have used the FEA technique to examine the effects of artificially replicating meniscal tears. The aim of this study is to investigate the effect of meniscal injury on knee biomechanics, by means of FEA, starting with real meniscal tears. Based on Magnetic Resonance (MR) images of 12 patients, 3D models of the distal femur, proximal tibia, cartilage, and menisci were obtained for each patient through the segmentation process. A preprocessing phase was then necessary to prepare the models for FEA. Finally, simulations were conducted to study the effects of lesions on stress, contact pressure, and meniscal extrusion. The simulation results showed that meniscal lesions, especially radial tears, increase the pressure between menisci and tibial cartilage, increase the maximum shear stress on menisci, and lead to meniscal extrusion. The integration of FEA with clinical data may provide surgeons with detailed insight, enabling them to decide whether surgical intervention is necessary.

Keywords: ACL Injury , Finite Element Analysis , Knee Biomechanics , Meniscal Tears

Over the years, patients with partial hand loss have relied on expensive prosthetics to recover some of the hand functionality. Fortunately, advancements in additive manufacturing desktop solutions allow transitional prosthetics prices to decrease. Therefore, the present work focused on providing a basic overview of the field and available low-cost 3D-printed upper-limb prosthetic devices. The aim was to develop a basic frame of reference on the field of transitional partial hand prosthetics. Concomitantly, this study also highlights additive manufacturing techniques on which further research can be done whilst helping to provide a new variant for an upper limb prosthetic device. The initial stages, current practices, and future possibilities were considered. Researchers and industry can utilize these findings to develop additional variants for the benefit of patients suffering from partial hand loss.

Keywords: amputation , machine learning , minor upper-limb loss , partial hand prosthetics , prostheses , transitional prosthesis

Injuries to the anterior cruciate ligament (ACL) are common among active populations. The shape and anatomical variations of the bones are directly related to the function of the ACL, and therefore are considered to be risk factors for injury. This research aims to delineate the key patterns of shape variation in femurs affected by ACL injuries through the application of Statistical Shape Modelling (SSM). SSM is applied to 50 distal femur models and their modes of variations are described. Ten morphologically significant parameters of the distal femur bone are selected and measured on a 3D model of the mean femur, as well as the -3SD and +3SD shapes of the first three principal components (PCs). The first principal component reflects the variation in size of the femur. The second principal component is mainly related to the width of the notch. A variation in the height of the medial posterior condyle is observed in the third principal component. Nevertheless, it is not as significant as with the first two PCs. The study presents a statistical shape model for characterizing the fundamental modes of geometric variation in femoral bones following an ACL injury. Knowing the bony morphological features associated with ACL injuries is crucial to tailoring treatment plans to each individual.

Keywords: ACL Injury , Anatomical Variation , Morphological parameters , Principal Component Analysis , Statistical Shape Modelling

Mechanical properties of human dentin have been the subject of numerous experimental studies. This paper collects the main results reported in literature, obtained by using different experimental techniques. Elastic, anelastic and plastic characteristics of dentin are examined including Young's modulus, shear modulus, Poisson's ratio, damping, yield and ultimate stress, hardness, fatigue, fracture toughness, creep and stress relaxation.

Keywords: dentin , FIMEC test , mechanical properties , mechanical tests , Scanning Electron Microscopy (SEM)

In recent years, nanomaterials based on Layered Double Hydroxides (LDHs) have received great attention from biomedical research owing to their physicochemical properties, high biocompatibility, as well as cellular absorption and environmental sensitivity. This work briefly presents various growth techniques of LDHs, focusing the attention on how they can be modified and functionalized for biomedical applications, in particular bone generation, therapy, targeted and controlled release of drugs, gene release, ophthalmic activities, and bio-imaging.

Keywords: Bio-imaging , Biomedical Applications , Drug release , Layered Double Hydroxides , LDH , Therapy

The human skeleton is the frame of the human body and is made up of bones of different shapes and characteristics. Some of the bones in the human body must have high resistance to static and dynamic forces. These forces are also exerted on bone replacement implants, which must have a high level of robustness. Some of the most important properties of bone material, although different in various regions of the body, are tensile and compressive strength. These properties could be tuned for prosthetic applications by using lattice structures that can be varied in shape, unit cell size, and strut thickness. One technique that could be used to fabricate such structures is selective laser melting (SLM), which builds a three-dimensional object layer by layer from a metal powder. Another major advantage of this technology is the ability to create many different shapes, as there is a high degree of design freedom. In addition, various metal powders can be used in SLM, including those that could be used for implants such as titanium. Another major advantage of this manufacturing process is the ability to easily customize the process to the size, shape, and other characteristics of the patient's bone structure. This work demonstrates the potential to adjust the tensile properties of objects with specific external dimensions by incorporating lattice structures and tailor them. This can impact both the ultimate tensile strength and maximum elongation, providing an opportunity for future research to more accurately replicate the properties of bone material and thereby establish an additively manufacturable bone replica for stress analysis in medical and sports research. Additionally, the surface roughness Ra, which measures approximately 10 to 15 µm, did not appear to have any significant effect on the tensile strength.

Keywords: Lattice structures , Medical Prosthetics , Selective Laser Melting

This paper examines the capabilities of injection moulding in the production of medical devices, with a particular focus on the potential of additive manufacturing in the construction of cooling channels. Conventionally, cooling channels in injection moulds have been limited to linear configurations. However, the size, integration and structure of the cooling channels have a massive impact on cooling efficiency, part quality, cycle time and overall process efficiency. This leads to the need for new structural manufacturing methods. The introduction of additive manufacturing offers freedom of design and the ability to create cooling channels that conform to the tool's geometry. With the new advantages introduced by additive manufacturing come new difficulties and innovations in the development of conformal cooling channels. Examined through a case study of a medical component in this paper. Producing cooling channels that conform to the complex contours of the mould requires complex design processes. This paper investigates the challenges of designing these channels to ensure precision and efficiency in the development of conformal cooling channels. A key focus is the comparative analysis between optimised cooling channels, crafted through additive manufacturing, and their conventionally machined counterparts. Using simulation techniques, the study examines the reduced temperatures achieved by the conformal channels compared to their conventional counterparts. The implications of integrating additive manufacturing into the injection moulding tool for medical devices are also discussed. By incorporating additive manufacturing into the process of creating the cooling channels, increased efficiency and reduced temperature are achieved, as demonstrated by the simulation results. Within the scope of this study, emphasis is placed on investigating the potential impact on part quality, manufacturing speed, and overall process efficiency, beyond the immediate benefits observed in cooling channel design.

Keywords: Additive Manufacturing , Conformal Cooling Channels , Metall-3D-Prinitng

In modern society, it is increasingly important to pay attention to healthy and aesthetic appearance. Orthodontic treatment can improve the position of teeth and jaw. A distinction was made between functional orthodontic and dentoalveolar therapies. Currently, various materials are used to produce brackets. In addition to conventional metal brackets made of steel, titanium, or gold, tooth-colored plastic brackets made of polycarbonate and ceramic brackets made of aluminum or zirconium oxide are used. [1, 2] The progressive development of CAD/CAM technology in recent years has opened new possibilities for computer-assisted orthodontic diagnostics and planning for dentoalveolar therapy. [3, 4] The aim of this study was to manufacture plastic brackets for fixed braces using simple additive production. For this purpose, a bracket sample was designed and produced with a filament printer (FDM-Fused Deposition Modelling) Ultimaker S3 (Ultimaker B.V., Watermolenweg 24191 PN Gel-dermalsen). The construction and design were created using CAD software (SolidWorks2021) and transferred to 3D printer's proprietary slicing software (Cura Version 4.12.0, Ultimaking ltd.). By adjusting the parameters (printing speed, temperature, etc.), it is possible to adapt the printed components. The printed miniature components were then optically and physically tested and analyzed.

Keywords: 3 D Printing , dentistry , fixed orthodontic treatment , synthetic brackets