Methods for medical applications

Virtual reality (VR) applications for surgical planning and mentoring are currently becoming more widespread. Within these fields of applications, haptic systems are crucial to help the understanding of the feedback provided by the tissue during the interaction with the surgical tool. The accuracy of the VR scenario is related to many aspects, among them the ability of the haptic device to provide the force feedback and thus the adoption of proper characterization and modeling of the soft tissue behavior during deformation. This paper presents the current development concerning a VR environment to be equipped with a force feedback haptic device to simulate and experience clamping in colorectal surgery. The reaction at the clamp handle is provided starting from a FEA of the contact between the surgical tool and the tissue, coupled with the kinematic analysis of the mechanism. Connecting the virtual scenario to a microcontroller board, the reaction force is applied to the the haptic device, shaped as a clamping tool handle, so that the user may experience the tissue impedence during clamping. By simulations made through Simscape, a concept is evaluated according to some simulation paths that involve common scenarios of the virtual reality experience (such as collision, partial or total clamping operation). The novelty of the research regards the system design oriented to increase the accuracy of the soft tissue material behaviour through a preliminary off-line dedicated FEA investigation. Through Simulink simulations, the system design is verified so that the VR system set-up may be carried out. The results highlighted: (a) a good correspondence among the theoretical study of the reference kinematism that the haptic device must reproduce; (b) the implementation of a bilinear material model, derived off-line from FEA, is suitable to capture hyperelastic and geometric non-linearities of the soft tissue; (c) the feasibility of the open loop haptic control in accordance to the explored kinematism. The final goal of the research is to propose a system design approach able to tune the VR experince for teaching and mentoring through a in-house set-up easy to be tailored.

Keywords: FEA , Force feedback , Metamodeling , Surgical simulation , Virtual prototyping

Approximately 50% of the adult global population is projected to suffer from some form of metabolic disease by 2050, including metabolic syndrome and diabetes mellitus. At the same time, this trend indicates a potential increase in the number of patients who will be in need of implant-supported reconstructions of specific bone regions subjected to inflammatory states. Moreover, physiological conditions associated with dysmetabolic subjects have been suggested to contribute to the severity of bone loss after bone implant insertion. However, there is a perspective evidence strengthening the hypothesis that custom-fabricated bioengineered scaffolds may produce favorable bone healing effects in case of altered endocrine or metabolic conditions. This perspective review aims to share a comprehensive knowledge of the mechanisms implicated in bone resorption and remodelling processes, which have driven researchers to develop metallic implants as the cobalt-chromium (Co-Cr) bioscaffolds, presenting optimized geometries that interact in an effective way with the osteogenetic precursor cells, especially in the cases of perturbed endocrine or metabolic conditions.

Keywords: 3D-printed scaffolds , cobalt-chromium (Co-Cr) bioscaffolds , customized medicine , endocrine metabolic and immune disorders , regenerative medicine , tissue engineering , translational medicine

In this work, a procedure for modelling and simulating conformal biomimetic scaffolds for bone tissue engineering is presented. Starting from a three-dimensional biomedical model of a real human mandible presenting a severe damage, a conformal shape was modelled and filled with an irregular beam network mimicking human trabecular bone. The material considered for the realization of the scaffold was hydroxyapatite derived from fish industry by-products, a material that is highly biocompatible to human bone. Several simulations were conducted on a beam-based wireframe model by varying the radius of the trabeculae, until reaching a stiffness of the scaffold equal to that of human bone. This represents a good design practice to avoid the stress shielding effect on growing bone tissue and functionality losses during bone regeneration. The resulting porosity and the average pore size, which are fundamental properties to ensure a proper vascularization of the growing tissue, were measured and compared to literature data, showing an acceptable agreement. The proposed beam-based approach for modelling and simulating conformal irregular scaffolds appeared as an interactive, fast, and versatile procedure that can be applied in the design stage of conformal biomimetic scaffolds for bone tissue regeneration.

Keywords: Bone Tissue Engineering , CAD Modelling , Mechanical Simulation

Cell adhesion is a phenomenon characterizing cell-environment interactions and affects cellular behavior. Cell-substrate adhesion is ensured by focal adhesions (FAs), which are multilayer protein complexes. External mechanical stimulus perceived by FAs is rapidly transmitted first to cytoskeleton load-bearing structures and finally to the nucleus thanks to an interlinked cellular architecture, thus inducing transcription mechanisms and changes in cell functionality. Prestress of cytoskeletal filaments allows mechanical information to be transferred along these stiffer transportation channels with respect to neighboring cell regions, thus avoiding the energy dissipation typical of soft matter. Peculiar items concerning adhesion mechanisms, i.e., stiffness inhomogeneity in cell architecture, and auto-supporting tension-based cell structure, can be effectively handled thanks to modeling strategies provided by finite element method (FEM), which represents a valid tool for simulating cell adhesion. With the aim of replicating experimental results and predicting cell behavior, useful guidelines for simulating cellular adhesion will be outlined in the proposed work.

Keywords: Cell Adhesion , Finite Element Method , Mechanotransduction

The growing cooperation between physicians and engineers have been producing increasingly sophisticated anatomical phantoms for the training and planning of Structural Heart Surgery. Trans-Septal Puncture (TP) is a percutaneous, non-invasive cardio chirurgical procedure used to access the heart Left Atrium from the Right Atrium through the Fossa Ovalis (FO), a region of the Inter Atrial Septum with reduced thickness. TP is technically challenging and requires dedicated teaching and a skillful operator; as a result, application of phantoms to TP training have been gaining increasing interest. The aim of the present work is to investigate the current state of the art in TP simulators. The Scopus and PubMed databases were analyzed and the bibliography of the most impacting articles was reviewed. The results can be summarized as follows: i) mold casting and additive manufacturing (AM) are the only technologies documented for phantoms creation; ii) silicone rubbers and Polyvinyl Alcohol Cryogel are the most used materials for mold casting while Polyjet polymers are the most used material for AM; iii) quantitative data on force and haptic feedback from IAS and FO simulacra is scarcely documented; iv) procedure image guidance can be simulated during the training.

Keywords: Additive Manufacturing , Material Characterization , Medical Phantoms , Silicone Casting , Trans-Septal Puncture

The use of customized surgical guides for the removal of bone tumors is an increasingly common practice in advanced hospitals. These devices are modeled directly on the 3D model of the patient's anatomy and produced using additive techniques; therefore, they have the ability to perfectly anchor to the bone anatomy and allow the tissue of the tumor mass to be removed according to cutting paths predetermined by the physician during preoperative planning. This work proposes a semi-automatic framework for modeling custom surgical guides composed of two main modules: 1) a web application, called Precise, that allows the surgeon to visualize and manipulate 3D anatomical models and enter a set of cutting planes that determine the correct tumor resection paths and other useful information for modeling the surgical guide; 2) a fully automatic procedure that based on this information creates the guide's STL model. The entire procedure aims to create a specific type of cutting guide designed to guide an oscillating saw in a series of planar cuts, thus isolating the tumor. The cutting guides produced are composed of three main elements: a base, the blade slot, and pin's holes.

Keywords: Medical 3D Model , Medical Application , Rapid Prototyping , Surgical Planning

Autologous ear reconstruction is a surgical procedure which aims to restore the anatomy of the outer ear whenever there are malformations due to congenital defects (microtia) or as a result of trauma and burns. Reconstruction involves the cutting, carving, and modeling of a portion of costal cartilage harvested from the patient. The aesthetic results of the surgery are highly dependent on the manual skill of the surgeon, which therefore needs a wide range of surgical experience. Appropriate simulation and training tools are essential to acquire adequate familiarity with the procedure without compromising the patient's aesthetic appearance. In such a context, the present work aims to create replicas of the costal cartilage that allow a realistic simulation of the surgery, thus taking into account important characteristics of the cartilage tissue such as the behavior to cut and suture, hardness, etc. The problem is approached with well-established Additive Manufacturing and Reverse Engineering techniques, which are increasingly being used in the medical field, addressing both the problem of identifying the most suitable materials and the possibility of providing medical personnel with simple interactive procedures for the fabrication of multilayer replicas, without the need to turn to expert CAD modelers.

Keywords: CAD modeling , Costal cartilage mold , Ear reconstruction , Medical simulation

Rheumatoid arthritis (RA), a chronic autoimmune disease, affects a significant portion of the elderly population and often poses challenges in performing essential activities of daily living. Simple tasks such as grasping an apple or holding cutlery can become arduous and painful for individuals with this condition. Consequently, many of them require rehabilitative procedures to re-establish the functionality of their hands. In this context, the implementation of a glove-based solution that incorporates pneumatic technology holds promising potential. By harnessing the power of pneumatic action, this innovative glove can provide valuable assistance in facilitating the squeezing movement of the hand. This assistance can prove immensely beneficial for individuals struggling with the debilitating effects of (RA). The primary objective of this project is twofold. Firstly, it aims to directly support patients in their daily activities by alleviating the challenges associated with hand movements affected by rheumatoid arthritis. The glove, through its pneumatic action, can enhance grip strength and provide the necessary support to perform tasks that were previously difficult or impossible. Moreover, the project strives to help patients regain lost mobility and independence. By actively assisting hand motions, the glove encourages engagement in rehabilitative exercises, contributing to the gradual restoration of dexterity and motor function. The dual purpose of this innovative glove is to not only offer immediate relief and assistance but also serve as a rehabilitative tool, fostering the long-term recovery of patients.

Keywords: CAD modeling , hand exoskeleton , rehabilitation , rheumatoid arthritis

In the last decades, the adoption of assistive devices has been spreading among different application fields, starting from the rehabilitative medicine to the industrial field. In particular, exoskeletons aimed to ease the operations performed by workers have been developed in order to reduce the entity of work-related musculoskeletal disorders, limiting the inconvenience caused to the workers and reducing therapy-related costs faced by the employer or the healthcare system. However, commercial full-body exoskeletons equipped with efficient, low-weight actuation systems require a huge investment (both for purchase and maintenance), which only a few companies are willing to pay. In order to achieve high performance while limiting costs and complexity, a custom cycloidal reduction was designed: because of its back-drivability and scalability, it represents a low-cost solution capable of maximizing the overall performances of the assistive device. In this paper, the methodology to define a custom low-cost yet efficient cycloidal drive actuation is hence proposed, as well as its implementation in the design of a low-back exoskeleton based on backbone kinematics.

Keywords: additive manufacturing , back-drivable reduction , cycloidal transmission , fast pro-totyping , FEM , low-back exoskeleton

Additive manufacturing (AM) of load-bearing metal implants allows sustainable production of personalized implants with complex shapes and inner architectures. Implants must meet strict requirements to not harm patients, and production technique must certify their performance. Available materials, many production parameters and implant personalization on patient's needs represent limits of AM. Layer-by-layer material deposition and repeated thermal cycles typical of AM may also cause discontinuities between layers affecting implant mechanical features, and its match to the host body. In this paper the mechanical challenges that AM must overcome to replace traditional manufacturing techniques are discussed, in order to better understand whether AM has to be limited to implant personalization for exceptional cases.

Keywords: Additive manufacturing , Conventional manufacturing , Geometric accuracy , Implants , Mechanical properties

Additive manufacturing (AM) permits sustainable production of personalized load-bearing metal implants with complex structures. Regulations prescribe that implants have to meet strict requirements to not harm patients, and production technique should allow the certification of their performance. Process, materials, operating parameters, and customization to patient's needs could limit AM. Layer-by-layer material deposition and repeated thermal cycles may make outer surface of AM implants chemically and physically uneven and rough, eliciting biological response of host tissue and hindering therapeutic success. In this paper, we discuss the clinical challenges that AM must overcome to replace traditional techniques in implant and prostheses design.

Keywords: Additive manufacturing , Clinical performance , Conventional manufacturing , Implants , Surface properties

Introduction: We report the development and preliminary evaluation of a novel dynamic bioreactor to culture ovarian cortical tissue strips that leverages tissue response to enhanced oxygen transport and adequate mechanical stimulation. In vitro multistep ovarian tissue static culture followed by mature oocyte generation, fertilization, and embryo transfer promises to use the reserve of dormant follicles. Unfortunately, static in vitro culture of ovarian tissue does not promote development of primordial to secondary follicles or sustain follicle viability and thereby limits the number of obtainable mature oocytes. Enhancing oxygen transport to and exerting mechanical stimulation on ovarian tissue in a dynamic bioreactor may more closely mimic the physiological microenvironment and thus promote follicle activation, development, and viability. Materials and Methods: The most transport-effective dynamic bioreactor design was modified using 3D models of medium and oxygen transport to maximize strip perifusion and apply tissue fluid dynamic shear stresses and direct compressive strains to elicit tissue response. Prototypes of the final bioreactor design were manufactured with materials of varying cytocompatibility and assessed by testing the effect of leachables on sperm motility. Effectiveness of the bioreactor culture was characterized against static controls by culturing fresh bovine ovarian tissue strips for 7 days at 4.8 × 10−5 m/s medium filtration flux in air at −15% maximal total compressive strain and by assessing follicle development, health, and viability. Results and Conclusions: Culture in dynamic bioreactors promoted effective oxygen transport to tissues and stimulated tissues with strains and fluid dynamic shear stresses that, although non-uniform, significantly influenced tissue metabolism. Tissue strip culture in bioreactors made of cytocompatible polypropylene preserved follicle viability and promoted follicle development better than static culture, less so in bioreactors made of cytotoxic ABS-like resin.

Keywords: bioreactor , dynamic culture , fluid dynamic stimulation , mechanical stimulation , ovarian tissue , oxygen transport

Background & objective: Human vertebrae are analysed and measured for various purposes, including to study anatomy, to diagnose illness, and to evaluate therapies. Achieving an accurate morphological and dimensional characterisation of three-dimensional (3D) vertebrae relies on the precise recognition of their features. Traditionally, these features, lacking defined edges, have been identified manually through a time-consuming, poorly repeatable, and poorly reproducible process. To the authors' knowledge, there is only one method published in the literature able to automatically recognise all the most important vertebral features: the algorithmic feature recognition method (AFRM). It requires a high-density point cloud as input, the presence of all morphological features, even if incomplete, and incurs high computational costs. This research aims to propose an improved version of the AFRM to overcome its limitations. Methods: The proposed approach combines the robustness of AFRM to provide the semantic segmentation of a 3D healthy human vertebra with the ability of the enhanced statistical shape model (eSSM) to transfer information among different models. Specifically, AFRM provides the semantic segmentation of the mean shape of the eSSM, while the latter transfers this information to target shapes. Results: The eSSM was developed using 20 training samples of healthy adult male L2 vertebrae. The test samples included five healthy vertebrae and four vertebras with large missing parts. None of the test shapes were included in the training set. The novel approach could accurately recognise morphological features without the constraints that affect the AFRM. Conclusion: The proposed method guarantees reliable and automated segmentation through AFRM, exploiting the eSSM's ability to provide results even when dealing with sparsely populated or partially incomplete target models, significantly reducing the computational load.

Keywords: 3D medical image analysis , Bio-informatics , Computer methods for vertebra analysis , Shape segmentation , Statistical Shape Analysis

Additive manufacturing presents unique opportunities for developing patient-specific medical devices and tools in orthognathic surgery. Devices used in maxillofacial surgery present several constraints which refer to the specific characteristics of the patient and the stress conditions that are in place during the surgery. This paper describes an integrated workflow used for the identification, design, optimization, and production of patient-specific devices while promoting synergy among specialists of vastly different backgrounds. Medical specialist interprets Computed Tomography scans with three-dimensional reconstruction of the patient and, supported by a CAD specialist design the required tools to restore the patient functionality. Preliminary tooling designs are checked for strength and stiffness by a structural engineer considering the mechanical properties of the perspective AM materials and passed in digital form to the AM technologist who will be responsible of the 3D printing. The medical specialist uses the devices through physical prototypes to assess effectiveness and usability. The integrated workflow allows to increase accuracy while reducing surgical time and costs.

Keywords: additive manufacturing , orthognathic surgery , reverse engineering , topology optimization

The paper focuses on the application of 3D printing technology in the medical field, particularly in cardiac surgery. Unlike traditional imaging techniques such as CT, MRI, and ultrasound, 3D printing offers a more detailed understanding and analysis of clinical cases. By using 3D printing, it becomes possible to study a patient's specific cardiac anatomy, manipulate objects before surgery, and accurately determine the surgical site. This reduces both the time required for the operation and the patient's recovery period. This study presents a methodology for creating 3D-printed models of aortic arch sections affected by aortic dissection. The aim is to produce anatomical models with varying levels of quality and accuracy. The research goal is to assess the differences in 3D printing materials and technologies for creating complex anatomical models like the aorta. The process involves segmenting medical images obtained from Computed Tomographic Angiography (CTA) and then 3D printing digital models using different materials (such as PLA, TPU, and resin) and technologies (like FDM and SLA). The resulting 3D printed models are low-cost and demonstrate good accuracy in reproducing human anatomy.

Keywords: 3D Printing , CAD , Cardiac surgery , Engineering method

Lung cancer is the second neoplasia for incidence and the leading cause of death from neoplasia in the world. A consolidated practice for lung cancer early diagnosis and staging is EBUS TBNA (EndoBronchial UltraSound-guided TransBronchial Needle Aspiration). Despite being a low-risk procedure, its success highly depends on the medical staff's skills, who therefore require appropriate training. With the future aim of developing a novel realistic EBUS TBNA simulator that also allows tissue sampling, in this paper, the authors propose a simplified representation of the mediastinum to define a suitable layout. As far as the authors know, the physical commercially-available simulators have poor echogenic properties, do not allow tissue sampling, and can be quite expensive. The project was carried out within Custom3D, a joint laboratory between Careggi Hospital of Florence and the Department of Industrial Engineering of the University of Florence, under the request of the interventional pneumology ward. The model was validated by an expert medical doctor who assessed its anatomical accuracy and the suitability of its mechanical and acoustic properties. Moreover, the possibility of performing lymph node needle aspiration is an added value that promises to bring the EBUS TBNA simulation to a new level of realism.

Keywords: EBUS TBNA , echogenic , mannequin , simulation

Background: Reports on hand dysfunction and rehabilitation in SSc are quite scarce in the literature and mainly focus on functional assessment tools, such as the Duruoz Hand Index and the HAMIS test for evaluating hand mobility by simulating specific grasps with nine different objects. Purpose of the study: This study aimed to provide an adequate assessment methodology for hand grasp dysfunctions in patients suffering from systemic sclerosis (SSc) through the 16-grasp test. Study design: Case-control study. Methods: Ninety-seven consecutive SSc patients were recruited at our Scleroderma Unit, where a 16-grasp test was performed by all patients and supervised by an experienced hand therapist. Sixteen different patterns of grasp have been divided into power grasps and precision pinch and two more modalities: static and dynamic prehension evaluation on scale from 0 to 4. We also compared previous evaluations on 19 of patients recruited. Results: The majority of SSc patients (84 females and 13 males; mean age 56.0±12.0 years; mean disease duration 8.0±6.0 years) displayed grasp dysfunctions; in particular 48% and 54% reported slight difficulty in the right and left grasps respectively, 6% medium difficulty in both hands, and only 3% and 1% experienced severe difficulty respectively, while 31.5% had no issues in either hand. Our results showed that the limited cutaneous subset (lcSSc) scored a lower deficit for either grasp compared to diffuse form (dcSSc). No statistically significant differences in total grasp deficit had been noticed when comparing patients having a disease duration < 5 years or longer. In the retrospective study on 19 of these patients, 8 out of 10 lcSSc patients showed no significant changes, while in 2 out of 10, slight improvements were observed in both hands. However, in the dcSSc group, 4 out of 9 worsened bilaterally while the grasp scores for 5 of them remained unchanged. Conclusion: Our study reported hand involvement in both lcSSc and dcSSc forms, more significantly in dcSSc patients. This test is intended to be a more objective means of assessing grasp alterations linked to scleroderma hand deformities. Furthermore, thanks to its intuitiveness, the test may be useful for engineers designing personalized ergonomic assistive devices.

Keywords: 16-grasp test , Connective tissue diseases , Digital skin , Hand rehabilitation , Scleroderma , Systemic sclerosis , Three-dimensional printing , Ulcers

The design of advanced devices is a paramount goal in the biomedical field. Current challenges include the development of customized devices with improved and tailored properties according to the specific application. Accordingly, the aim of the study was to report some recent efforts in the design of advanced biomedical devices, especially focusing on dental implants and hybrid structures for cranioplasty.

Keywords: Additive Manufacturing , Biomedical Applications , Design for Additive Manufacturing

Postpartum haemorrhage (PPH) is an obstetric emergency causing nearly one-quarter of maternal deaths worldwide, 99% of these in low-resource settings (LRSs). Uterine balloon tamponade (UBT) devices are a non-surgical treatment to stop PPH. In LRSs, low-cost versions of UBT devices are based on the condom balloon tamponade (CBT) technique, but their effectiveness is limited. This paper discusses the experimental study to assess the usability and performance of a medical device, BAMBI, designed as an alternative to current CBT devices. The testing phase involved medical and non-medical personnel and was focused on testing BAMBI's usability and effectiveness compared to a standard CBT solution. We collected measures of the execution time and the procedure outcome. Different training procedures were also compared. Results show a significant preference for the BAMBI device. Besides, medical and non-medical subjects reached comparable outcomes. This aspect is highly relevant in LRSs where the availability of medical personnel could be limited

Keywords: Maternal mortality , Medical device , Patient safety , Sustainable development goals , Usability , User-centered design , Uterine balloon tamponade device

Manipulating patient data acquired by Computer tomography (CT), e.g., anatomical shape and geometry, as well as studying the biomedical devices used in patient care, is certainly of remarkable importance. Here, Medical Re- verse Engineering (MRE) and Rapid Prototyping (RP) play a key role in the 3D models reconstruction of patient anatomy, that can be exploit to make patient- specific, custom-made devices. The inherent variability of the human anatomy can be a problem, which is why the concept of custom-made devices is men- tioned. In this field, MRE exploits the computational tools provided by Statistical Shape Modelling (SSM) and Principal Component Analysis (PCA) to achieve computer modelling of 3D data from real models. The PCA is a statistical tool for reducing the number of variables in a population, while the SSM enables the development of an infinite digital population of a given anatomy. This paper aims to show the potential of SSM in the field of the MRE. The study will focus on the pathological lumbar spine. Here, SSM provides new pathological geometries of the lumbar spine, which can be extrapolated and used to produce customized biomedical devices for that given pathological deformation, as well as to perform Finite Element (FE) simulations. Therefore, utilising SSM can bring an addi- tional edge to MRE, due to the infinite population of CAD models of patient anatomy, which can be useful in the medical industry, as already pointed out.

Keywords: Lumbar spine , Medical Reverse Engineering , Patient-specific , Statistical Shape Modelling