Methods for medical applications

By definition, osseointegration means close contact between bone and implant. Bone response is related to implant surface properties. Various surfaces have been studied and applied to improve the biological properties of the implant and thereby favor the mechanism of osseointegration. This strategy aims to promote osseointegration by means of a faster and stronger bone formation, improving stability during the healing process, and thus allowing for earlier loading of the implant. Dental implant osseointegration has so far been studied in various animal models. The development of a method based on tissue engineering for assessing the osseointegration process in vitro could prove a valid biomimetic alternative to sacrificing animals. In this study, flat cylindrical dental implants with moderately rough surfaces and machined implants were set in bovine bone blocks. Then, adipose-derived stem cells (ADSCs) were three dimensionally cultured onto these blocks in osteo-endothelial medium for up to 30 days to mimic the osseointegration process in vitro. Scanning electron microscopy (SEM) and gene expression were used to examine stem cell commitment. Mechanical pull-out tests were also performed. SEM analysis identified cells with an osteoblast morphology adhering to the surface of the implants after their removal. Gene expression analysis showed that ADSCs seeded onto the bone blocks were able to express osteoblast and endothelial markers. The implants with the moderately rough surface generated higher pull-out strengths when compared with the machined implants. Nevertheless, the pull-out test values were higher for implants placed in bone blocks with ADSCs than for those set in scaffolds without stem cells. Our results demonstrate the validity of the method adopted and its potential for use in the in vitro assessment of the biological behavior of dental implant surfaces.

Many systems have been developed to facilitate upper limb rehabilitation procedures in human subjects affected by trauma or pathologies and to retrieve information about patient performance. The Microsoft Kinect sensor can be used in this context to track body motion and detect objects. In order to evaluate the usability of this device in the upper limb rehabilitation field, a comparison with a marker-based system is presented in this paper. The upper limb motion is specifically considered and the performance on its detection and tracking is evaluated. The effect of the relative location between the Kinect and the observed subject is also investigated through experimental tests performed in different configurations.

Keywords: Kinect V2 , Upper limb joints tracking , Upper limb rehabilitation

In this work an hypothesis of modeling nanofibers network of Poly-L-lactide (PLLA) scaffolds loaded with hydroxyapatite (HA) nanoparticles, suitable for tissue engineering applications, is presented to investigate the mechanical properties by FEM analysis. Scaffolds were produced by Supercritical CO2 drying of polymeric gels. FEM modeling of nanoporous biomaterials involves computational problems such as: the reproduction of the nano-morphology by means of different techniques, such as molecular dynamics simulations that hardly lead to results adherent to the experimental evidence; the reverse engineering to extrapolate geometric information; the identification of a periodic representative volume element (RVE) to reach more coherent results and to reduce the simulation computational effort. Basic modeling assumptions are: a) polymer particles are small enough to exhibit Brownian motion; b) scaffold SEM images show that the porous structure consists of curved fibers that depart from punctiform nuclei realizing a space frame; c) scaffold experimental compressive tests show that the porous material behaves as a soft isotropic material. On the basis of these assumptions, a parametric algorithm that creates a cubic RVE, showing a nanofibers network and having the same porosity of the real material, has been written; RVE size has been optimized on the bases of its material isotropic degree measured by an ad hoc created iterative algorithm for generating a rod spaceframe; RVE mechanical behavior has been optimized by curving appropriately each fiber according to the experimental data and on the basis of SEM imaging diagnostic. Linear FEM simulations on mechanical behavior have given qualitatively and quantitative satisfactory results when compared to the experimental ones.

Pier Paolo Valentini, PhD in Design of Mechanical Systems, is Associate Professor of Applied Mechanics. He is research fellow of the National Laboratories of Frascati (Rome) of the Italian Institute for the Nuclear Physics and member of the Steering Committee of the Italian Association of Machine Design. He teaches Virtual Prototyping and Simulation of Mechanical Systems and Bio-prosthesis. He has been advisor of more than 130 master and PhD dissertations. He has been principal investigator of more than 40 research projects funded by institutions and industrial partners. He has authored more than 130 papers in international journals and conference proceedings. Eugenio Pezzuti is Associate Professor of Machine Drawing. He is member of the advisory board of the Italian Ministry for Education, University and Research. He has been the principal investigator of three projects funded by national institutions. His fields of interests are the design of machine components, study on optimal tolerance allocations, reverse engineering methodologies and biomechanics. He has authored more than 80 papers in international journals and conference proceedings. The allocation of the right tolerances is one of the most important phases in the design process of mechanical devices and systems. In general, the choice has to take into account the manufacturing costs and limitations, looking at the specific functionality of the device and the assemblability of parts. In the case of flexible components, the designer has to include the evaluation of the compliance effects and the structural resistance. The paper discusses a numerical methodology for addressing the problem of the geometrical tolerance allocation for the compliant ortho-planar spring. The methodology is based on the definition of the functionality and resistance objective functions by means of finite element models. Numerical constrained optimisation is then applied to find the suitable combination of tolerance parameters acting on the main dimensions.

Keywords: Compliant mechanism , Flexible component , Ortho-planar spring , Tolerance allocation

Purpose: The purpose of this study was to characterize the biomechanical effect of two grasping suture techniques used during ligament reconstruction: the modified rolling-hitch (MRH) and the modified finger-trap (MFT). Methods: Flexor profundus tendons were harvested from fresh pig hind-leg trotters. Each specimen was mounted on an electro-mechanic universal testing machine (Instron 3367). In half of all tendons (15 specimens), the suture was passed around the tendon following the MRH knot (Group 1). In the remaining half of all tendons (15 specimens), the suture was passed over a distance of 30 mm according to the MFT suture technique (Group 2). As per standard intra-operative technique, a 1 cm residual tendon stub was left free from suture in all samples. All specimens were preconditioned to a load of 50 N for 10 min, followed by three cycles loading between 50 and 120 N. At this point, each sample was cyclically tensioned between 35 and 240 N, at 1 Hz for 200 cycles. Load-to-failure test was then carried out at a rate of 200 mm/min. Results: Rupture of the suture material at the knot was the mode of failure in all specimens during the loaded to failure test. Significant difference was found between Group 1 vs Group 2 for the elongation between the 0th cycle and 10th cycle, the elongation between the 10th cycle and 200th cycle, the mean stiffness at the 10th cycle, and the mean stiffness at the 190th cycle. No significant differences were noted between Group 1 and Group 2 concerning the ultimate load-to-failure. Conclusion: This study showed that both suture methods appear to be biomechanically effective in a porcine tendon model. However, the single-knot grasping technique (MRH) provided superior biomechanical properties compared with the MFT technique.

Keywords: Biomechanics grasping suture , FiberWire suture , Grasping suture , Modified finger-trap , Rolling-hitch , Suture ligament

Human acellular dermal matrices (HADMs) are used in reconstructive surgery as scaffolds promoting autologous tissue regeneration. Critical to the HADM ability to remodel and integrate into the host tissue is the removal of cells while maintaining an intact extracellular architecture. The objective of this work is to develop a methodology to analyse the mechanical properties of HADMs after decellularization to identify its ideal form of treatment and its duration. Two different decellularization techniques were used as a benchmark: the first is a well-established technique (incubation in NaOH for 1–7 weeks), and the second is an innovative technique developed by this research group (incubation in DMEM (Dulbecco's modified Eagle medium) for 1–7 weeks). After decellularization, the specimens underwent uniaxial tensile tests, and experimental data were represented with stress strain curves, calculating both engineering and true values. Mechanical tests have led to the identification of the optimal method (NaOH or DMEM) and duration for the decellularization treatment; differences between engineering and true values can reach 84%, but the engineering values remain useful to make comparisons, providing reliable indications with a simpler experimental set up and data processing.

Keywords: Decellularization treatment , Human dermis , Static mechanical tests , Ultimate strain , Ultimate stress , Young's modulus

Background: The dermis is a commonly used source tissue for biologic scaffolds; all cellular and nuclear materials need to be removed to limit the inflammatory immune response by the host organism. The decellularization is critical because it must preserve the structural integrity of the extracellular matrix. This work has analyzed a decellularization procedure commonly followed for the dermal tissue that is a chemical treatment with sodium hydroxide. The goal of this work is to identify the optimal treatment length on the basis of structural properties. Methods: Tensile tests have been performed on the native tissue and on tissues decellularized for 1-7 weeks in sodium hydroxide. The collected data have been analyzed through Tukey-Kramer test to assess if the mechanical properties (ultimate tensile stress and elastic modulus) of decellularized tissues were significantly different from the properties of the native tissue. These tests have been performed on specimens cut along two orthogonal directions (parallel and perpendicular to Langer's lines). Results: The decellularization treatment performed with sodium hydroxide in general weakens the tissue: both the ultimate stress and the elastic modulus get lower. The structural properties along Langer lines orientation are more strongly impacted, while the structural properties orthogonal to Langer lines can be preserved with an optimal duration of the decellularization treatment that is 5-6 weeks. Conclusion: The duration of the decellularization treatment is critical not only to reach a complete decellularization, but also to preserve the mechanical properties of the tissue; 5-6 week treatment performed with sodium hydroxide allows preserving the mechanical properties of the native tissue perpendicularly to Langer lines orientation, and minimizing the impact of the decellularization process on the mechanical properties along the Langer lines orientation.

Keywords: Acellularized dermis , Allografts , Decellularization treatment , Elastic modulus , Extracellular matrix , Human dermis , Tensile tests , Ultimate stress

Objectives: The purpose of this study was to describe the force generated by two different removal devices used to retrieve cemented crowns on implant abutments. The influence of six different operators was evaluated. Material and methods: Three replicated Coronaflex® (Kaltenbach & Voigt GmbH, KaVo Dental GmbH) and reverse hammer setups were tested. The experimental setup has employed a screw bearing a diametral hole through which a loop holder passed. The screw was attached to a force transducer (Brüel & Kjær, type 8201), and the loop holder arm was kept perpendicular to the transducer axis. The results were statistically evaluated with ANOVA. Results: The operator has resulted to play significant influence with reference to reverse hammer (coefficient of variation 43.3%) rather than with Coronaflex® (9.8%). Evaluating every single operator, more variation can still be found by considering each reverse hammer (37.5%) rather than each Coronaflex® (8.8%). Conclusion: Coronaflex® device was found to systematically reach a more repeatable and higher peak amplitude of forces compared with reverse hammer, both by experienced and inexperienced operators.

Keywords: Coronaflex® , FDP , Force transducer , Implant prosthesis , Reverse hammer

In this paper a new automatic approach to determine the accurate measure of human vertebrae is proposed. The aim is to speed up the measurement process and to reduce the uncertainties that typically affect the measurement carried out by traditional approaches. The proposed method uses a 3D model of the vertebra obtained from CT-scans or 3D scanning, from which some characteristic dimensions are detected. For this purpose, specific rules to identify morphological features, from which to detect dimensional features unambiguously and accurately, are put forward and implemented in original software. The automatic method which is here proposed is verified by analysing real vertebrae and is then compared with the state-of-the-art methods for vertebra measurement.

Keywords: 3D medical-image analysis , Computer methods for vertebra analysis , Measurement accuracy , Measurement protocols in biomedicine , Shape segmentation , Vertebral dimensions

Custom-fit products, such as artificial prostheses, often require the development of hoc modeling tools and procedures. In such a context, this paper describes an open source library, named Simply NURBS, developed for NURBS modeling in medical and health-care domains. This new suite makes available a development kit that integrates the key features of existing open source libraries and new ones to fulfill the requirements of the considered domain. First, the paper introduces the library requirements with particular attention to the prosthetic field as well as pros and cons of current NURBS modeling libraries (both commercial and open sources). Then, the software architecture of Simply NURBS and the basic libraries (e.g., OPENCASCADE and NURBS++) used for its implementation are illustrated enhancing differences and improvements. Finally, a socket modeling tool, named Virtual Socket Laboratory (VSL) developed using SimplyNURBS is described as well as results of tests carried out to evaluate the new system performances.

Keywords: Nurbs , Open source libraries , Prosthetic socket

The diffusion of depth sensors to sense people and objects constitutes an outstanding opportunity in those fields in which the benefits of optical marker-less solutions for scanning or tracking are requested. This paper shows how two different applications based on MS Kinect device can be accomplished in the domain of lower limb prosthesis design and test. The first one refers to the use of a depth camera as a three-dimensional scanner to acquire the geometry of residual limbs or of custom-fit components. The second application is related to the motion capture of patients' gait with the prosthesis. In both cases, the technology resulted to be better than many traditional ones mainly for its limited invasivity, interesting performance, portability and low cost.

Keywords: 3D scanner , Digital human modelling , Lower limb prosthesis , Motion capture , RGB-D cameras

The diffusion of depth sensors to sense people and objects constitutes an outstanding opportunity in those fields in which the benefits of optical marker-less solutions for scanning or tracking are requested. This paper shows how two different applications based on MS Kinect device can be accomplished in the domain of lower limb prosthesis design and test. The first one refers to the use of a depth camera as a three-dimensional scanner to acquire the geometry of residual limbs or of custom-fit components. The second application is related to the motion capture of patients' gait with the prosthesis. In both cases, the technology resulted to be better than many traditional ones mainly for its limited invasivity, interesting performance, portability and low cost.

Keywords: 3D scanner , Digital human modelling , Lower limb prosthesis , Motion capture , RGB-D cameras

This paper presents a software module, named tracking plug-in, developed to automatically generate the source code of software interfaces for managing the interaction with low cost hand-tracking devices (e.g., Leap Motion and Intel Gesture Camera) and replicate/emulate manual operations usually performed to design custom-fit products, such medical devices and garments. The proposed solution is based on the Eclipse platform, a free integrated development environment (IDE), that allow us to manage the automatic code generation in a simple way after having defined the target application using a meta-model language, in our case the UML class diagram. First, we describe the background as well as the main problem, then, the software solution and adopted tools (i.e., Eclipse and Acceleo). Finally, the preliminary tests carried out for two applicative contexts (prosthetic and textile/clothing) are presented.

The present paper describes the research done to empirically validate the use of RGB-D cameras for orthopedic rehabilitation purposes. In order to assess the outcome of optical sensors a set of new generation inertial sensors have been adopted as well. Both kind of sensors have been used to track the same scene simultaneously in order to have comparable results. The aim of the work is provide evidence of performances of the newly introduced sensors (optical and inertial) and to automate acquisition and data elaboration in the medical field. The extraction of the only meaningful data from a gait, for instance, gives the change to perform an automatic preliminary analysis on normal people as well as on patients with known pathologies or disorders. In particular, this could allow determining without human intervention any standard disorders, according to literature classifications, eventually affecting the gait. The automatic procedure from acquisition to diagnosis constitutes a challenging topic of research and a success in terms of reliability, usability and physiological acceptance by technicians would radically impact medical practices in orthopedic rehabilitation centers.

This paper concerns the development of a Natural User Interface (NUI) for lower limb prosthesis design. The proposed solution exploits the Leap Motion device to emulate traditional design tasks manually performed by the prosthetist. We first illustrate why hand-tracking devices can be adopted to design socket of lower limb prosthesis using virtual prototyping tools. Then, we introduce the developed NUI and its features mainly with regards to ergonomics and ease of use. Finally, preliminary tests are illustrated as well as results reached so far.

Keywords: Augmented interaction , Hand-tracking devices , SMA

The research work presented in this paper is part of an innovative framework that deals with the design process of lower limb prostheses. The quality of the whole prosthesis depends on the comfort of the socket, which realizes the interface between the patient body and the mechanical parts. We developed a CAD system, named Socket Modelling Assistant that guides the user during the design of the socket, exploiting domain knowledge and design rules. In this work we present a preliminary study that describes the implementation of a software module able to automatically identify the critical areas of the residuum to adequately modify the socket model and reach the optimal shape. Once the critical areas have been identified, the Socket Modelling Assistant can apply proper geometry modifications, in order to create the load and off-load zones for a good pressure distribution over the residual limb.

Keywords: CAD , Lower limb prosthesis , Neural network , Prostheses socket

The paper concerns the use of integrated methodologies and tools to perform innovative human centered development of products. Digital simulation of ergonomics by means of DHM is shown together with advanced tools for design, taking into account Knowledge-based systems, Design Automation and design of highly customized goods. Two different applications of the proposed approach are described, the first refers to an industrial product, the second to the medical domain. Both applications, even if belonging to completely different fields benefit from putting the human at the center of the developing paradigm from the very first step of product development. Some results and discussion highlight benefits and limitation of the approach and of the adopted tools.

Keywords: Design Automation , Digital human modelling , Ergonomics , Human centered design , Knowledge-based systems , Lower limb prosthesis

In the field of orthodontic planning, the creation of a complete digital dental model to simulate and predict treatments is of utmost importance. Nowadays, orthodontists use panoramic radiographs (PAN) and dental crown representations obtained by optical scanning. However, these data do not contain any 3D information regarding tooth root geometries. A reliable orthodontic treatment should instead take into account entire geometrical models of dental shapes in order to better predict tooth movements.This paper presents a methodology to create complete 3D patient dental anatomies by combining digital mouth models and panoramic radiographs. The modeling process is based on using crown surfaces, reconstructed by optical scanning, and root geometries, obtained by adapting anatomical CAD templates over patient specific information extracted from radiographic data. The radiographic process is virtually replicated on crown digital geometries through the Discrete Radon Transform (DRT). The resulting virtual PAN image is used to integrate the actual radiographic data and the digital mouth model. This procedure provides the root references on the 3D digital crown models, which guide a shape adjustment of the dental CAD templates. The entire geometrical models are finally created by merging dental crowns, captured by optical scanning, and root geometries, obtained from the CAD templates.

The reconstruction of tooth anatomies is of utmost importance when dental implant surgeries and/or orthodontic corrections must be planned. In the last few years, cone beam CT (CBCT) has gained popularity in dentistry for 3D imaging of jawbones and teeth. However, within CBCT data sets, each tooth is defined by a region, which cannot be easily separated from surrounding tissues (i.e., bone tissue) by only considering pixel's grey-intensity values. For this reason, some enhancement is usually necessary in order to properly segment tooth geometries. In this paper, a semi-automatic approach to reconstruct individual 3D tooth anatomies by processing CBCT-scan data is presented. The methodology is based on the creation of a minimal number of 2D "local ray-sum" images by adding the absorption values of adjacent voxels along the most significant views for each tooth. The knowledge of the specific anatomical patient morphology drives the selection of these significant projection directions. The reconstructed "ray-sum" images greatly enhance the clearness of the root contours, which can then be interactively traced by dentists. A set of meaningful 2D tooth contours is consequently obtained and used to automatically extract a cubic spline curve for each transverse slice, thus approximating the overall 3D tooth profile. The effectiveness of the methodology has been evaluated by comparing the results obtained for the reconstruction of anterior teeth with those obtained by using classical segmentation tools provided within commercial software.

Within the orthodontic field, malocclusion problems are usually treated by using different types of appliances. In particular, Eruption Guidance Appliances (EGAs) are recommended for early orthodontic treatment or prevention of malocclusion problems. The traditional approach with EGAs is based on the use of standard prefabricated appliances. Experts in the orthodontic field believe that the customization of the EGAs would strongly enhance the results of malocclusion treatments. This paper presents an innovative methodology for the design and manufacturing of fully customized EGAs. The methodology is based on an extensive integration between traditional orthodontic procedures with advanced computer aided design processes. The methodology moves from the digitalization of the plaster models obtained by optical scanning techniques. The patient morphology is then exploited, under dental practitioner supervision, for the design of the appliance geometry through CAD modeling tools. Medical guided assessment is required throughout the most of the data elaboration processes, in order to design the EGAs accordingly to the patient's clinical conditions. Low-pressure injection molds for the physical manufacturing of the appliances are then 3D printed by using rapid prototyping techniques. The proposed methodology allows the production of patient customized appliances guaranteeing low cost manufacturing and high quality standards, similar to those typically obtained by in series productions. Moreover, the presented approach offers a high integration level with numerical and finite element methods, which can be used for evaluating the stress applied on the EGA, thus allowing the reinforcement of the appliance prior its manufacturing.