Methods for medical applications

Finite Element Analysis (FEA) has gained an extensive application in the medical field, such as soft tissues simulations. In particular, colorectal simulations can be used to understand the interaction with the surrounding tissues, or with instruments used in surgical procedures. Although several works have been introduced considering small displacements, as a result of the forces exerted on adjacent tissues, FEA applied to colorectal surgical scenarios is still a challenge. Therefore, this work aims to provide a sensitivity analysis on three geometric models, taking in mind different bioengineering tasks. In this way, a set of simulations has been performed using three mechanical models named Linear Elastic, Hyper-Elastic with a Mooney-Rivlin material model, and Hyper-Elastic with a YEOH material model.

Keywords: Computer assisted surgical planning , Finite element analysis , Soft tissues simulation , Surface modeling

Enhancing the performance of scaffolds for bone regeneration requires a multidisciplinary approach involving competences in the fields of Biology, Medicine and Engineering. A number of studies have been conducted to investigate the influence of scaffolds design parameters on their mechanical and biological response. The possibilities offered by the additive manufacturing techniques to fabricate sophisticated and very complex microgeometries that until few years ago were just a geometrical abstraction, led many researchers to design scaffolds made from different unit cell geometries. The aim of this work is to find, based on mechanobiological criteria and for different load regimes, the optimal geometrical parameters of scaffolds made from beam-based repeating unit cells, namely, truncated cuboctahedron, truncated cube, rhombic dodecahedron and diamond. The performance, -expressed in terms of percentage of the scaffold volume occupied by bone-, of the scaffolds based on these unit cells was compared with that of scaffolds based on other unit cell geometries such as: hexahedron and rhombicuboctahedron. A very intriguing behavior was predicted for the truncated cube unit cell that allows the formation of large amounts of bone for low load values and of very small amounts for the medium-high ones. For high values of load, scaffolds made from hexahedron unit cells were predicted to favor the formation of the largest amounts of bone. In a clinical context where medical solutions become more and more customized, this study offers a support to the surgeon in the choice of the best scaffold to be implanted in a patient-specific anatomic region.

Keywords: Beam-based scaffolds , Bone tissue engineering , Diamond , Mechanobiology , Rhombic dodecahedron , Truncated cube , Truncated cuboctahedron , Unit cell

In a context more and more oriented towards customized medical solutions, we propose a mechanobiology-driven algorithm to determine the optimal geometry of scaffolds for bone regeneration that is the most suited to specific boundary and loading conditions. In spite of the huge number of articles investigating different unit cells for porous biomaterials, no studies are reported in the literature that optimize the geometric parameters of such unit cells based on mechanobiological criteria. Parametric finite element models of scaffolds with rhombicuboctahedron unit cell were developed and incorporated into an optimization algorithm that combines them with a computational mechanobiological model. The algorithm perturbs iteratively the geometry of the unit cell until the best scaffold geometry is identified, i.e. the geometry that allows to maximize the formation of bone. Performances of scaffolds with rhombicuboctahedron unit cell were compared with those of other scaffolds with hexahedron unit cells. We found that scaffolds with rhombicuboctahedron unit cell are particularly suited for supporting medium-low loads, while, for higher loads, scaffolds with hexahedron unit cells are preferable. The proposed algorithm can guide the orthopaedic/surgeon in the choice of the best scaffold to be implanted in a patient-specific anatomic region.

Keywords: Computational mechanobiology , Morphology optimization , Rhombicuboctahedron , Scaffold unit cell

Design of scaffolds for tissue engineering entails multi-disciplinary and multi-scale aspects. Since in vivo analysis of the tissue regeneration process is quite difficult in terms of selecting experimental protocols and requires considerable amount of time, a variety of numerical models have been developed to simulate mechanisms of tissue differentiation. The tremendous enhancement in computing power led researchers to develop more and more sophisticated models mostly based on finite element techniques and mechano-regulation computational models. In this article, we present an algorithm that combines the finite element model of an open-porous scaffold, a numerical optimization routine and a mechanobiological model. This algorithm has been utilized to determine both, the best scaffold geometry and the best load value (to apply on the scaffold) that allow the bone formation to be maximized.

Keywords: Bone tissue scaffold , Computational mechanobiology , Geometry optimization , Scaffold micro-architecture

Background: New sources of stem cells in adult organisms are constantly emerging. Postnatal Mesenchymal Stem Cells (MSCs), are the most promising support to perform an effective regenerative medicine: such cells have the ability to differentiate into several lineages, such as osteoblasts and chondroblasts, providing novel strategies to improve different complex treatments, during bone regeneration. 3D-printed biomaterials can be designed with geometry aimed to induce stem cells to differentiate towards specific lineage. Objective: The interaction between stem cells easy to isolate and engineered 3D-printed scaffolds can translate the tissue bio-engineering into bone regenerative surgery. For those reasons, to better identify the complexity represented by the activities and responses of MSCs requires the advance of new target therapies which are not current in endocrine, metabolic and immune disorders and yet to be developed. Method: This topical review briefly focuses on the new approaches of translational medicine with the use of MSCs and scaffolds engineered with the aid of 3D-printing technology, highlights the osteogenic functions and addresses their applications across the breadth of regenerative medicine. Results: The application of bone constructs consisting of the engineered scaffold and MSCs as well as the aspects related to the optimal scaffold geometry that favours the best MSCs differentiation and the improvement of concepts as “sensing surface” were also discussed. Conclusion: Regenerative surgery is largely growing in the field of translational medicine. The use of new sources of MSCs and the improvement of new concepts of bio-engineered scaffolds will certainly be the next step of customized medicine.

Keywords: 3D-printed scaffolds , Customized medicine , Mesenchymal stem cells , Regenerative medicine , Tissue engineering , Translational medicine

Thanks to the recent advances of three-dimensional printing technologies the design and the fabrication of a large variety of scaffold geometries was made possible. The surgeon has the availability of a wide number of scaffold micro-architectures thus needing adequate guidelines for the choice of the best one to be implanted in a patient-specific anatomic region. We propose a mechanobiology-based optimization algorithm capable of determining, for bone tissue scaffolds with an assigned geometry, the optimal value Lopt of the compression load to which they should be subjected, i.e. the load value for which the formation of the largest amounts of bone is favoured and hence the successful outcome of the scaffold implantation procedure is guaranteed. Scaffolds based on hexahedron unit cells were investigated including pores differently dimensioned and with different shapes such as elliptic or rectangular. The algorithm predicted decreasing values of the optimal load for scaffolds with pores with increasing dimensions. The optimal values predicted for the scaffolds with elliptic pores were found higher than those with rectangular ones. The proposed algorithm can be utilized to properly guide the surgeon in the choice of the best scaffold type/geometry that better satisfies the specific patient requirements.

Keywords: Computational Mechanobiology , Hexahedron Unit Cell , Numerical Optimization Algorithms , Printing of Biomaterials , Scaffolds for Bone Tissue Engineering

Patients suffering from Spinal Cord Injury (SCI) can partially restore their walking function over ground and reduce of the secondary pathologies thanks to a frequent use of powered exoskeletons for robot-assisted gait. However, many of these devices require crutches to stabilize the body or to initiate the step. This could induce high loads on the shoulder joints, leading to shoulder pain and pathologies in SCI patients. This study presents a methodology to evaluate shoulder joints loads during robotic assisted gait, which was applied to an expert user of a Rewalk® exoskeleton. A pair of wireless instrumented crutches, designed by the authors[1], measure the crutches' forces and movements. A simplified mechanical model of the patient is then simulated in OpenSim to perform both inverse kinematic and inverse dynamic analysis. Such a system could be applied during the initial training of new users, to help guide both patient and therapist towards an optimal usage of the exoskeleton.

Keywords: Measurements , Rewalk , Robotic assisted gait , Upper limbs

The growing potential of virtual reality (VR) systems presents an immense opportunity for amputee patients who are suffering from the medical condition which causes sensation of pain at the location of the missing limb called Phantom Limb Pain (PLP). The occurrence rate of PLP is reported 60–80% [1] among amputee patients and treatment methods vary between physical therapy, surgery and medication. One of the proven treatment methods is “Mirror Therapy” [3] and it is applied by visually projecting a healthy limb on the amputated part with the help of a mirror to create the perception of presence. Similar approach can also be represented in a virtual environment and immersion of VR can enhance the rehabilitation experience. Therefore, we aimed to improve the mirror therapy treatment by a VR application and to overcome the physical limitations by presenting potentially engaging activities with a way to treat double-limb amputees.

Keywords: Mirror therapy , Phantom Limb Pain , Tele-rehabilitation

The optimization of loading protocols following dental implant insertion requires setting up patient-specific protocols, customized according to the actual implant osseointegration, measured through quantitative, objective methods. Various devices for the assessment of implant stability as an indirect measure of implant osseointegration have been developed. They are analyzed here, introducing the respective physical models, outlining major advantages and critical aspects, and reporting their clinical performance. A careful discussion of underlying hypotheses is finally reported, as is a suggestion for further development of instrumentation and signal analysis.

Keywords: Damping , Early loading , Functional loading , Implant stability , Modal analysis , Osseointegration , Resonance frequency , Reverse torque , Ultrasound

OBJECTIVE The aim of this study is the evaluation of the temporomandibular joint stress distribution during the use of a Mandibular Advancement Device. MATERIALS AND METHODS This study is made using Finite Element Method (FEM). Dental casts, advancement bite, CBCT and MRI were taken in a 27-year-old woman. A Somnodent device was scanned and associated with a three-dimensional cranium. FEM analysis was made using ANSYS software with 1 and 2 mm of advancement. RESULTS The articular disc showed values range between 0.099-6.39 and 0.5-2.02 MPa for an advancement of 1 and 2 mm respectively. The condyle load distribution showed values range between 0.0037-7.50 and 0.0020-10.0 MPa for an advancement of 1 and 2 mm respectively. CONCLUSIONS Values obtained are significantly lower than limit values of the condyle and articular disc. Slight mandibular advancement can be consider a safe procedure even for the long period and should not cause permanent side effects.

Keywords: CBCT , Finite Element Method , Mandibular advancement device , OSAS , Temporomandibular joint

The paper aims to evaluate the effects caused by a Mandibular Advancement Device (MAD) for Obstructive Sleep Apnoea Syndrome (OSAS) treatment. This study is based on Finite Element Method (FEM) for evaluating the load distribution on temporomandibular joint, especially on the mandibular condyle and disc, and on periodontal ligaments. The stress values on condyle and periodontal ligaments lead authors to consider MAD a safe procedure even for a long period. The obtained results also show the relationship between MAD material and load distribution at the periodontal ligaments. The paper is a step toward future analyses for studying and comparing the effects of MAD features, such as material, shape and dimensions, in order to allow the clinician prescribing the most fitting device.

Keywords: Finite element method , mandibular advancement device , obstruction sleep apnea syndrome , periodontal ligament , temporomandibular joint

This paper presents a knowledge-based method and relative multi-user web platform to prescribe Custom Made Insoles (CMI) involving the various stakeholders (patients/customers, practitioners, manufacturers and controllers) in an integrated approach that covers the entire process. The CMI prescription and design are carried out by using configuration rules, which combine foot parameters with insoles features. The platform also offers functionalities to collect and monitor the patients feedbacks, to control the clinician work and to obtain an electronic insole order used by manufactures.

Keywords: Co-design , Custom-made insole , Design knowledge , Healthcare design , Knowledge-based process

Wrist injuries are one of the most common fractures, specifically around 25% of fractures among the pediatric population and up to 18% in the elderly age group are distal radius fractures. To date, the standard treatment entails the use of a tailor-made plaster of Paris cast. Although it is a simple and reliable treatment, it presents several disadvantages: its weight generally causes discomfort, it cannot be taken off without breaking it, it can cause skin rashes and prevents ventilation of the treated area. To overcome the limitations of the above mentioned treatment, 3D printed orthopaedic casts based on reverse engineering (RE) and additive manufacturing (AM) techniques have been proposed in literature. Despite these solutions prove to be a valid alternative to the standard treatment, the clinical use of AM-based devices is not trivial due to the need of expert CAD modelers to design the 3D model of the orthosis starting from the patient's anatomy 3D acquisition. In this work, the authors identify a systematic procedure to create an orthosis model, compliant with medical guidelines, using common CAD tools. The systematic procedure, even still manually performed, envisages a set of tasks, grouped into five main blocks, that will be easy to be automatized in the future, thus eliminating the necessity of designing expertise to model the orthosis. The proposed procedure allows to design a device composed of two halves, to ease the application, locked through a zip tie-based mechanism. A preliminary ventilation pattern is proposed and tested with a FEM analysis to ensure structural resistance. The procedure has been tested on six case studies: all the orthoses models were correctly generated without major complications and positive user feedbacks were generally obtained throughout the tests.

Keywords: Cad , Cast modeling , Orthosis modelling , Personalized medicine , Reverse engineering

The surgical process adopted to repair cranial defects using an implant, typically called Cranioplasty, has seen an abrupt increase in recent years due to the introduction of Reverse Engineering (RE) and Additive Manufacturing (AM) techniques. By adopting these techniques, CT/MRI data can be used to reconstruct, in a pre-operative stage, the 3D anatomy of the defective skull in order to design a patient-specific digital model of the prosthesis. The so-designed cranial plate can be then fabricated via AM, in a suitable metal alloy, and implanted. This allows for a perfect fit of the implant during the actual surgery, reducing the risks for the patient and increasing the efficacy of the treatment. This paper reviews existing approaches for the virtual reconstruction of defective skulls, and a basic classification, proposing four different classes of strategies (Mirroring, Surface Interpolation, Template-Based and Slice-based techniques) is provided. The findings of the study suggest that the reconstruction of skull defects is still an open problem, due to the complexities imposed by surface that needs to be retrieved (i.e. the human anatomy). All the presented approaches share weaknesses and limits, which are discussed in the article. Finally, possible directions to improve the existing techniques are briefly presented.

Keywords: Biomedical engineering , Cranioplasty , Reverse engineering , Skull reconstruction

This paper analyse and compare the methods to detect and represent the human symmetry line. In the last years, the development of 3D scanners has allowed to replace the traditional techniques (marking based methods) with modern methodologies that, starting from a 3D valid discrete geometric model of the back, perform the posture and vertebral column detection based on a complex processing of the acquired data. The purpose of the paper is a critical discussion of the state of the art in order to highlight real potentialities and limitations of the most important methodologies proposed for human symmetry line detection.

Keywords: Anatomical landmarks , Back shape analysis , Posture prediction , Rasterstereography , Symmetry line

BACKGROU ND: The aim of this paper was to develop a scoring system to grade the risk of rupture of an abdominal aortic aneurysm (AAA ) in individual patients. METHODS: Computed tomography angiography of an AAA were coupled with computational fluid dynamics (CFD) evaluation performed using open source software (ElmerSolver, Institute of Technology, Espoo, Finland). CFD criteria studied were: Oscillatory Shear Index (OSI ), time averaged wall shear stress (TAWSS ) and residence relative time (RR T) on both two-dimensional (2D) and three-dimensional (3D) models. AAA rupture predictors were analyzed and a scoring system was generated using Arabic numerals for all significant variables in order to grade the individual patient risk of rupture. RESUL TS: There were 143 patients examined. Ninety-one AAA s (18 ruptured AAA s), and 52 had a non-aneurysmal aorta. The 2D OSI was the best CFD criterion following multivariate analysis and RO C curves evaluation. An AAA was deemed respectively at low, moderate, or high risk of rupture, according to whether the risk score was defined as AAA I (total score <2.3), AAA II (2.3-6.5) or AAA III (>6.5). The only protective factor was found in diabetes (OR =0.775; CI: 0.665-0.902). CONCLUSIO NS: The Florence Risk Score for AAA rupture based on this report may be a useful tool to predict AAA rupture. A prospective multicenter registry will need to confirm its validity.

Keywords: Aortic aneurysm abdominal , Rupture , Surgical procedure operative

The present paper aims at discussing the current manufacturing processes of chest orthoses, considering patients affected by Osteogenesis Imperfecta (OI) and a possible future scenario. OI is a genetic disease caused primarily by the genes responsible for collagen production. One of the most common symptoms among the groups of living subjects affected by OI is scoliosis, the abnormal deformation of the spine curvature. The non-invasive treatments for realigning the spine consist of both physical exercise and use of chest braces. The latter are strongly patient-dependent devices; thus, the level of customization is high. The production processes can be classified in: traditional, modern and research process. The first one consists of a sequence of manual operations on plaster casts and final orthoses. The modern process integrates CAD/CAM systems for the first phases of virtual 3D modeling and the automation of the cast production using milling robot, but maintaining the second part of the process. The research process considers the introduction of polymer Additive Manufacturing (AM) in substitution to the thermoforming. Advantages and disadvantages related to each process are discussed in relation to the OI problem.

The aim of this ex vivo study was to test a novel three-dimensional (3D) automated computer-aided design (CAD) method (aCAD) for the computation of femoral angles in dogs from 3D reconstructions of computed tomography (CT) images. The repeatability and reproducibility of three manual radiography, manual CT reconstructions and the aCAD method for the measurement of three femoral angles were evaluated: (1) anatomical lateral distal femoral angle (aLDFA); (2) femoral neck angle (FNA); and (3) femoral torsion angle (FTA). Femoral angles of 22 femurs obtained from 16 cadavers were measured by three blinded observers. Measurements were repeated three times by each observer for each diagnostic technique. Femoral angle measurements were analysed using a mixed effects linear model for repeated measures to determine the levels of intra-observer agreement (repeatability) and inter-observer agreement (reproducibility). Repeatability and reproducibility of measurements using the aCAD method were excellent (intra-class coefficients, ICCs ≥ 0.98) for all three angles assessed. Manual radiography and CT exhibited excellent agreement for the aLDFA measurement (ICCs ≥ 0.90). However, FNA repeatability and reproducibility were poor (ICCs < 0.8), whereas FTA measurement showed slightly higher ICCs values, except for the radiographic reproducibility, which was poor (ICCs < 0.8). The computation of the 3D aCAD method provided the highest repeatability and reproducibility among the tested methodologies.

Keywords: Canine , Computed tomography , Femur , Repeatability , Reproducibility , Three-dimensional constructions

Advances in additive manufacturing technologies facilitate the fabrication of cellular materials that have tailored functional characteristics. The application of solid freeform fabrication techniques is especially exploited in designing scaffolds for tissue engineering. In this review, firstly, a classification of cellular materials from a geometric point of view is proposed; then, the main approaches on geometric modeling of cellular materials are discussed. Finally, an investigation on porous scaffolds fabricated by additive manufacturing technologies is pointed out. Perspectives in geometric modeling of scaffolds for tissue engineering are also proposed.

The impairment of finger movements after a stroke results in a significant deficit in hands everyday performances. To face this kind of problems different rehabilitation techniques have been developed, nevertheless, they require the presence of a therapist to be executed. To overcome this issue have been designed several apparatuses that allow the patient to perform the training by itself. Thus, an easy to use and effective device is needed to provide the right training and complete the rehabilitation techniques in the best way. In this paper, a review of state of the art in this field is provided, along with an introduction to the problems caused by a stroke and the consequences for the mobility of the hand. Then follows a complete review of the low cost home based exoskeleton project design. The objective is to design a device that can be used at home, with a lightweight and affordable structure and a fast mounting system. For implementing all these features, many aspects have been analysed, starting from the rehabilitation requirements and the ergonomic issues. This device should be able to reproduce the training movements on an injured hand without the need for assistance by an external tutor.

Keywords: Hand rehabilitation , Post stroke , Tele-Rehabilitation