Arturo N Natali

University of Padova, Padua, Veneto, Italy

Are you Arturo N Natali?

Claim your profile

Publications (92)177.58 Total impact

  • Silvia Todros · Piero G. Pavan · Paola Pachera · Arturo N. Natali
    [Show abstract] [Hide abstract]
    ABSTRACT: This work reports the second part of a review on synthetic surgical meshes used for abdominal hernia repair. While material and structural characteristics, together with mesh–tissue interaction, were considered in a previous article (Part I), biomechanical behavior is described here in more detail. The role of the prosthesis is to strengthen the impaired abdominal wall, mimicking autologous tissue without reducing its compliance. Consequently, mesh mechanical properties play a crucial role in a successful surgical repair. The main available techniques for mechanical testing, such as uniaxial and biaxial tensile testing, ball burst, suture retention strength, and tear resistance testing, are described in depth. Among these methods, the biaxial tensile test is the one that can more faithfully reproduce the physiological loading condition. An outline of the most significant results documented in the literature is reported, showing the variety of data on mesh mechanical properties. Synthetic surgical meshes generally follow a non-linear stress–strain behavior, with mechanical characteristics dependant on test direction due to mesh anisotropy. Ex-vivo tests revealed an increased stiffness in mesh explants due to the gradual ingrowth of the host tissue after implant. In general, the absence of standardization in test methods and terminology makes it difficult to compare results from different studies. Numerical models of the abdominal wall interacting with surgical meshes were also discussed representing a potential tool for the selection of suitable prostheses.
    No preview · Article · Dec 2015 · Journal of Biomedical Materials Research Part B Applied Biomaterials
  • Silvia Todros · Piero G. Pavan · Arturo N. Natali
    [Show abstract] [Hide abstract]
    ABSTRACT: Surgical implants are commonly used in abdominal wall surgery for hernia repair. Many different prostheses are currently offered to surgeons, comprising permanent synthetic polymer meshes and biologic scaffolds. There is a wide range of synthetic meshes currently available on the market with differing chemical compositions, fiber conformations, and mesh textures. These chemical and structural characteristics determine a specific biochemical and mechanical behavior and play a crucial role in guaranteeing a successful post-operative outcome. Although an increasing number of studies report on the structural and mechanical properties of synthetic surgical meshes, nowadays there are no consistent guidelines for the evaluation of mechanical biocompatibility or common criteria for the selection of prostheses. The aim of this work is to review synthetic meshes by considering the extensive bibliography documentation of their use in abdominal wall surgery, taking into account their material and structural properties, in Part I, and their mechanical behavior, in Part II. The main materials available for the manufacture of polymeric meshes are described, including references to their chemical composition, fiber conformation, and textile structural properties. These characteristics are decisive for the evaluation of mesh-tissue interaction process, including foreign body response, mesh encapsulation, infection, and adhesion formation.
    No preview · Article · Dec 2015 · Journal of Biomedical Materials Research Part B Applied Biomaterials
  • Silvia Todros · Piero Pavan · Arturo N. Natali
    [Show abstract] [Hide abstract]
    ABSTRACT: Synthetic meshes are widely used for surgical repair of different kind of prolapses. In the light of the experience of abdominal wall repair, similar prostheses are currently used in the pelvic region, to restore physiological anatomy after organ prolapse into the vaginal wall, that represent a recurrent dysfunction. At this purpose, synthetic meshes are surgically positioned in contact with the anterior and/or posterior vaginal wall, to inferiorly support prolapsed organs. Nonetheless, while mesh implantation restores physiological anatomy, it is often associated with different complications in the vaginal region. These potentially dangerous effects induce the surgical community to reconsider the safety and efficacy of mesh transvaginal placement. At this purpose, the evaluation of state-of-the-art research may provide the basis for a comprehensive analysis of mesh compatibility and functionality. The aim of this work is to review synthetic surgical meshes for pelvic organs prolapse repair, taking into account the mechanics of mesh material and structure, and to relate them with pelvic and vaginal tissue biomechanics. Synthetic meshes are currently available in different chemical composition, fiber and textile conformations. Material and structural properties are key factors in determining mesh biochemical and mechanical compatibility in vivo. The most significant results on vaginal tissue and surgical meshes mechanical characterization are here reported and discussed. Moreover, computational models of the pelvic region, which could support the surgeon in the evaluation of mesh performances in physiological conditions, are recalled.
    No preview · Article · Oct 2015 · Journal of the Mechanical Behavior of Biomedical Materials
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this work is to investigate the mechanical response of the plantar soft tissue from the heel strike to the midstance, developing both experimental and numerical activities. Using force plates and motion tracking system, the dynamic and kinematic data of 10 subjects are evaluated. The average kinematics data obtained from the experimental tests are assumed as boundary and loading conditions for the computational analyses. A three-dimensional virtual solid model of the foot is developed from the analysis of Digital Imaging and Communications in Medicine images from computed tomography and magnetic resonance. Constitutive formulations that interpret the mechanical response of the biological tissues are defined. Because of the major role of plantar soft tissue in the proposed analysis, a specific visco-hyperelastic constitutive formulation is provided considering the typical features of the tissue mechanics. The three-dimensional numerical model permits to evaluate the capability of the plantar soft tissue to redistribute the deformations, especially during the midstance, and to define quantitative aspects related to the energy absorption. The numerical results highlight the stress distribution from the heel strike to the midstance. The values of stress and strain reached are more intensive during the midstance, when there is a single support of the foot.
    No preview · Article · Oct 2015 · Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A coupled experimental and computational approach is provided for the identification of the structural behaviour of gas-trointestinal regions, accounting for both elastic and visco-elastic properties. The developed procedure is applied to characterize the mechanics of gastrointestinal samples from pig colons. Experimental data about the structural behaviour of colonic segments are provided by inflation tests. Different inflation processes are performed according to progressively increasing top pressure conditions. Each inflation test consists of an air inflow , according to an almost constant increasing pressure rate, such as 3.5 mmHg/s, up to a prescribed top pressure, which is held constant for about 300 s to allow the development of creep phenomena. Different tests are interspersed by 600 s of rest to allow the recovery of the tissues' mechanical condition. Data from structural tests are post-processed by a physio-mechanical model in order to identify the mechanical parameters that interpret both the non-linear elastic behaviour of the sample, as the instantaneous pressure–stretch trend, and the time-dependent response, as the stretch increase during the creep processes. The parameters are identified by minimizing the discrepancy between experimental and model results. Different sets of parameters are evaluated for different specimens from different pigs. A statistical analysis is performed to evaluate the distribution of the parameters and to assess the reliability of the experimental and computational activities.
    Full-text · Article · Sep 2015 · Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background An accurate investigation of esophageal motility was adopted as basis for computational tools addressed to a reliable and efficient diagnosis of motor disorders. A number of models have been proposed in literature to interpret data from HRM. Results are often inadequate because of an improper evaluation of the complex esophageal conformation and the heterogeneous distribution of physiomechanical properties. Furthermore, little effort was paid to identify relationships between model parameters and esophageal properties. Finally, the model parameters identification has usually been performed accounting for limited sets of experimental data. Aim The investigation proposed aimed at providing a procedure capable to autonomously diagnose esophageal motor disorders by processing raw data from HRM. The action was taken to support the action of medical staff and to reduce interand intraobserver variability that is currently affecting the traditional diagnostic process. Materials and methods The procedure was designed accounting for a physiological model [1] able to interpret pressure distribution due to peristaltic waves transit. Such model accounts for parameters defined in consideration of the heterogeneous distribution of esophageal properties. A reference set of 261 subjects was classified into groups, as non pathological (H) (106 patients + 35 volunteers), achalasia I (AP1) (35), achalasia II (AP2) (49), hypertensive LES (HLES) (9), jackhammer esophagus (JHE) (15) and DES (12). Model parameters were identified for each subject and their statistical distributions were subsequently assessed. According to the developed algorithm, the condition of a generic subject can be determined by evaluating a specifically designed similarity index that correlates the model parameters of the subject to the parameters distribution of the groups. Results A reliable (R2=[83%,96%]) physiological model was developed to interpret HRM measurements and the identified model parameters were used to implement an autonomic diagnostic procedure. The global success rate of the algorithm was 86.24%, being maximum in achalasia (96.15%) and minimum in the hypertensive LES group (55.5%). The percentage of the different groups of subjects is reported in figure, for a direct interpretation of procedure performance. Conclusions Results suggest the suitability of the procedure as a reliable tool to support the diagnostic activity. The assumed database can be extended to improve the statistical reliability of the procedure developed, as already in progress. [1] Carniel EL, Frigo A, Costantini M, Giuliani T, Nicoletti L, Merigliano S, Natali AN. A physiological model for the investigation of esophageal motility in healthy and pathologic conditions. Submitted: Medical Engineering and Physics.
    Full-text · Conference Paper · Aug 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: The plantar fat pad of the human foot is a specific tissue made up of adipose chambers enveloped by fibrous septa. Aging, pathology or trauma may affect its histo-morphological configuration and mechanical response. The correlation between histo-morphological configuration and mechanical properties is analyzed by a computational approach, aiming to identify the influence of degenerative phenomena on plantar fat pad mechanics. Finite element meso-models, as numerical model of an intermediate-length scale, are developed for healthy and degenerative conditions, considering the different properties that degenerative phenomena may affect, such as the adipose chambers dimension, the fibrous septa thickness, the fibers orientation and the sub-components mechanical behavior. Histo-morphometric data are analyzed to identify average configurations of the fat chambers and fibrous septa, while specific constitutive formulations are provided to define their mechanical response. Numerical analyses are performed to identify the stress-strain behavior of the plantar fat pad considering healthy and degenerative configurations. The results from meso-models are applied to identify the parameters of a phenomenological constitutive formulation that interprets the overall human fat pad tissue mechanics. The constitutive formulation is implemented within a 3D finite element model of the heel region that is applied to evaluate the influence of degenerative phenomena on the overall mechanical functionality of the foot.
    No preview · Article · Aug 2015 · Medical & Biological Engineering
  • [Show abstract] [Hide abstract]
    ABSTRACT: A procedure for the constitutive analysis of bladder tissues mechanical behavior is provided, by using a coupled experimental and computational approach. The first step pertains to the design and development of mechanical tests on specimens from porcine bladders. The bladders have been harvested, and the specimens have been subjected to uniaxial cyclic tests at different strain rates along preferential directions, considering the distribution of tissue fibrous components. Experimental results showed the anisotropic, non-linear and time-dependent stress-strain behavior, due to tissue conformation with fibers distributed along preferential directions and their interaction phenomena with ground substance. In detail, experimental data showed a greater tissue stiffness along transversal direction. Viscous behavior was assessed by strain rate dependence of stress-strain curves and hysteretic phenomena. The second step pertains the development of a specific fiber-reinforced visco-hyperelastic constitutive model, in the light of bladder tissues structural conformation and experimental results. Constitutive parameters have been identified by minimizing the discrepancy between model and experimental data. The agreement between experimental and model results represent a term for evaluating the reliability of the constitutive models by means of the proposed operational procedure. Copyright © 2015 Elsevier Ltd. All rights reserved.
    No preview · Article · Jul 2015 · Journal of Biomechanics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Engineered skeletal muscle tissues have been proposed as potential solutions for volumetric muscle losses, and biologic scaffolds have been obtained by decellularization of animal skeletal muscles. The aim of the present work was to analyse the characteristics of a biologic scaffold obtained by decellularization of human skeletal muscles (also through comparison with rats and rabbits) and to evaluate its integration capability in a rabbit model with an abdominal wall defect. Rat, rabbit and human muscle samples were alternatively decellularized with two protocols: n.1, involving sodium deoxycholate and DNase I; n.2, trypsin-EDTA and Triton X-NH4OH. Protocol 2 proved more effective, removing all cellular material and maintaining the three-dimensional networks of collagen and elastic fibers. Ultrastructural analyses with transmission and scanning electron microscopy confirmed the preservation of collagen, elastic fibres, glycosaminoglycans and proteoglycans. Implantation of human scaffolds in rabbits gave good results in terms of integration, although recellularization by muscle cells was not completely achieved. In conclusion, human skeletal muscles may be effectively decellularized to obtain scaffolds preserving the architecture of the extracellular matrix and showing mechanical properties suitable for implantation/integration. Further analyses will be necessary to verify the suitability of these scaffolds for in vitro recolonization by autologous cells before in vivo implantation.
    Full-text · Article · Jul 2015 · International Journal of Molecular Sciences
  • [Show abstract] [Hide abstract]
    ABSTRACT: Bioprostheses obtained from animal models are often adopted in abdominal surgery for repair and reconstruction. The functionality of these prosthetic implants is related also to their mechanical characteristics that are analyzed here. This work illustrates a constitutive model to describe the short-term mechanical response of Permacol™ bioprostheses. Experimental tests were developed on tissue samples to highlight mechanical non-linear characteristics and viscoelastic phenomena. Uni-axial tensile tests were developed to evaluate the strength and strain stiffening. Incremental uni-axial stress relaxation tests were carried out at nominal strain ranging from 10% to 20% and to monitor the stress relaxation process up to 400 s. The constitutive model effectively describes the mechanical behavior found in experimental testing. The mechanical response appears to be independent on the loading direction, showing that the tissue can be considered as isotropic. The viscoelastic response of the tissue shows a strong decay of the stress in the first seconds of the relaxation process. The investigation performed is aimed at a general characterization of the biomechanical response and addresses the development of numerical models to evaluate the biomechanical performance of the graft with surrounding host tissues.
    No preview · Article · Jun 2015 · Journal of Mechanics in Medicine and Biology
  • Piero G Pavan · Paola Pachera · Carla Stecco · Arturo N Natali
    [Show abstract] [Hide abstract]
    ABSTRACT: The present work focuses on the numerical modeling of the mechanical behavior of the crural fascia, the deep fascia enwrapping the lower limb muscles. This fascia has an important biomechanical role, due to its interaction with muscles during contraction and its association with pathological events, such as compartment syndrome. The mechanical response of the crural fascia is described by assuming a hyperelastic fiber-reinforced constitutive model, with families of fibers disposed according to the spatial disposition of the collagen network, as shown in histological analyses. A two-dimensional finite element model of a lower limb transversal section has been developed to analyze deformational behavior, with particular attention on interaction phenomena between crural fascia and enwrapped muscles. The constitutive model adopted for the crural fascia well fits experimental data taken along the proximal-distal and medial-lateral directions. The finite element analysis allows for interpreting the relation between change in volume and pressure of muscle compartments and the crural fascia deformation.
    No preview · Article · May 2015 · Medical & Biological Engineering
  • Source

    Full-text · Conference Paper · May 2015
  • Piero G Pavan · Paola Pachera · Arturo N Natali
    [Show abstract] [Hide abstract]
    ABSTRACT: The interaction of the crural fascia with muscular compartments and surrounding tissues can be at the origin of different pathologies, such as compartment syndrome. This pathology consists in the onset of excessive intracompartmental pressure, which can have serious consequences for the patient, compromising blood circulation. The investigation of compartment syndrome etiology also takes into account the alteration of crural fascia mechanical properties as a cause of the syndrome, where the fascial stiffening would result in the rise of intracompartmental pressure. This work presents a computational approach toward evaluating some biomechanical aspects of the problem, within the context of a more global viewpoint. Finite element analyses of the interaction phenomena of the crural fascia with adjacent regions are reported here. This study includes the effects of a fascial stiffness increase along the proximal-distal direction and their possible clinical implications. Furthermore, the relationship between different pre-strain levels of the crural fascia in the proximal-distal direction and the rise of internal pressure in muscular compartments are considered. The numerical analyses can clarify which aspects could be directly implied in the rise of compartment syndrome, leading to greater insight into muscle-fascia mechanical phenomena, as well as promoting experimental investigation and clinical analysis of the syndrome. © IMechE 2015.
    No preview · Article · May 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The biomechanical response of foot with regard to interaction phenomena occurring at interface with insole inserted in the shoe is investigated by using a numerical approach. At this purpose, a complex three-dimensional model of the foot is defined from biomedical images, while insole conformation is acquired by laser scanner technique, leading to the finite element discretization. Foot tissues are characterized by means of specific constitutive visco-hyperelastic anisotropic formulations, recalling previous research activity. The mechanical behavior of insole material is analyzed by means of experimental compression tests that highlight the geometric and material non-linear response, represented by a hyperelastic formulation, while a hyperfoam formulation is assumed for the sole. Numerical analysis considers the mid-stance phase of the gait and allows to interpret the response of overall foot, insole and sole system. The investigation represents a preliminary step of a parametric analysis addressed to support footwear design considering different configurations of components. As matter of example, the influence of variation in insole material properties is reported.
    Full-text · Article · Dec 2014 · Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Motor disorder of the GI tract may be considered as one of the most relevant social-health problems, and proper understanding of the motility of the GI tract should allow to provide tools for a reliable and rapid detection and treatment of different disorders. Computational models can be developed aiming to interpret the physiological and mechanical functionality of the GI tract and to summarize the results from experimental measurements, as HRM pressure plots, into model parameters. A physio-mechanical model was here developed to interpret data from esophageal HRM, accounting for parameters that are related to physiological and mechanical properties of the biological structures. The identification of parameters was performed by a procedure that minimizes the discrepancy between model results and raw data from esophageal HRM. Raw data were collected from both healthy volunteers (n=35) and patients with different motor disorders: Achalasia pattern 1 (n=13), 2 (n=20) and 3 (n=5); DES (n=69); EGJ outflow obstruction (n=25); Nutcracker esophagus (n=11); Normal motility (n=42). The model proved to be a reliable tool for the interpretation of HRM data, giving R2 ranging between 0.83 and 0.96. The study led to identify statistical distributions of parameters for both volunteers and patients. Accounting for the parameters distributions, an automatic procedure was finally implemented to perform diagnoses of esophageal diseases with reliable results, as the healthy or pathological conditions were correctly detected in the 87% of the subjects. These results address the suitability of the developed procedure to provide valid and dependable additional support to the clinical diagnosis of esophageal motor disorders.
    Full-text · Conference Paper · Nov 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effect of steam on the micro-phase structure and mechanical properties of different block copolymers used in biomedical devices is investigated via FT-IR, tensile tests and dynamic mechanical analysis (DMA). Steam sterilization, commonly performed on medical devices and simulated in this work, affects the copolymers' morphology, due to high temperature and humidity conditions. FT-IR analysis reveals that steam induces a modification in the crystalline conformations of copolymers with a pre-existing hydrogen bonding network, that is, thermoplastic polyurethanes (TPU) and poly(ether-block-amide) (PEBA), while it does not significantly affect the domain conformation in styrenic block copolymers (SEBS), due to weak interaction with water. As a consequence, relevant changes of the mechanical properties, closely related to the microdomain structure, are found for TPU and PEBA after sterilization, while SEBS mechanical behavior remains stable, as demonstrated by tensile tests and DMA results. For this reason, SEBS is suggested as the best choice in terms of durability in biomedical applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014
    No preview · Article · Oct 2014 · Journal of Polymer Science Part B Polymer Physics
  • Piero G Pavan · Paola Pachera · Cesare Tiengo · Arturo N Natali
    [Show abstract] [Hide abstract]
    ABSTRACT: This work aims to present a constitutive model suitable to interpret the biomechanical response of human pericardial tissues. The model is consistent with the need of describing large strains, anisotropy, almost incompressibility, and time-dependent effects. Attention is given to human pericardial tissue because of the increased interest in its application as a substitute in reconstructive surgery. Specific, even limited, experimental investigation has been performed on human samples taken from surgical grafts in order to verify the capability of the constitutive model in supplying a correct description of tissue mechanical response. Experimental data include uni-axial tensile tests and stress relaxation tests up to 300 s, developed along different directions of the tissue. The grafts tested show different mechanical characteristics for what concern the level of anisotropy of the tissue. The constitutive model proposed shows to adapt to the different configurations of the human pericardium grafts, as emerged by experimental data considered, and it is capable to describe the variability of the mechanical characteristics.
    No preview · Article · Sep 2014 · Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this work is to provide a numerical approach for the investigation of the mechanical behaviour of the forefoot soft tissues. The development of reliable numerical models of biological structures requires the definition of constitutive formulations that actually interpret the mechanical response of the constituent biological tissues and their structural arrangement. A specific visco-hyperelastic constitutive model is provided to account for the typical features of soft plantar tissue mechanics, as geometric and material non-linearity, almost-incompressible behaviour and time-dependent phenomena. Constitutive parameters are evaluated by the analysis of experimental data from compression and stress relaxation tests on tissue samples. A three-dimensional finite element model of the forefoot region is developed starting from the analysis of biomedical images, leading to the evaluation of overall structural response. The reliability of model and analyses is assessed by the comparison of experimental and numerical results pertaining to indentation tests. The numerical model developed allows to evaluate the mechanical response of plantar soft tissue in terms of stress and strain distribution.
    Full-text · Article · Sep 2014 · Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine
  • [Show abstract] [Hide abstract]
    ABSTRACT: This work reports the evaluation of the mechanical behaviour of Telemark ski boots, by means of an integrated approach, considering polymeric material characterisation, reported in a previous study (Part I), and numerical structural analysis, reported in this study (Part II). Telemark boots entail a complex procedure for analysis of the mechanical response, with regard to both material assumption and overall structural behaviour, and represent a reference problem within sky footwear in consideration of this peculiar complexity. A visco-elastic constitutive model is formulated to describe the material mechanical response defined in accordance with experimental test performed. Solid models define the morphology of the ski boots and represent the basis for numerical modelling. Specific boundary conditions are assumed to mimic the binding effect. The numerical analysis leads to an interpretation of the global and local responses of a specific Telemark ski boot, considering material properties and structural conformation. The results provide valid information on the ski boot mechanical response, taking into account also the effects of temperature on material response and strain rate with regard to loading conditions. The evaluation of variations in shape and material of the different components can be performed representing a fundamental support for the design.
    No preview · Article · Aug 2014 · Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study reports the first part of the analysis for the evaluation of the mechanical behaviour of ski boots by means of an integrated approach that considers polymeric materials characterization, in Part I, and numerical structural analysis, in Part II. In the present Part I, different techniques are adopted to characterize the mechanical behaviour of the polymeric materials used for ski boots, to define the elastic, visco-elastic, temperature and weathering-dependent characteristics. Experimental data provide fundamental information on mechanical response, in particular taking into account the effect of the environmental conditions, due to temperature variation, ultraviolet radiation and water absorption, which are correlated to the definition of reliability and durability of the materials. In more detail, experimental results from tensile tests and dynamic mechanical analysis are reported, evaluating mechanical response and chemical conformation of the polymers. Materials properties are correlated with the specific use conditions and boot structure, to be able to evaluate and preserve overall performances and general safety requirements of ski boots. This activity represents a reference procedure for the evaluation of the material mechanical behaviour that must be considered within the structural analysis.
    No preview · Article · Aug 2014 · Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology