Influence of transurethral catheters on urine pressure-flow relationships in males: A computational fluid-dynamics study.

Background And Objective: In the field of urology, the pressure-flow study (PFS) is an essential urodynamics practise which requires the patient's transurethral catheterization during the voiding phase of micturition to evaluate the functionality of the lower urinary tract (LUT) and reveal the pathophysiology of its dysfunctionality. However, the literature evidences confusion regarding the interference of the catheterization on the urethral pressure-flow behaviour.

Methods: The present research study represents the first Computational Fluid-Dynamics (CFD) approach to this urodynamics issue, analysing the influence of a catheter in the male LUT through case studies which included the inter-individual and intra-individual dependence.

A review of the effects of some endocrinological factors on respiratory mechanics.

Context: Endocrinological factors have been recently described to affect respiratory mechanics.

Objective: To review recent literature data, most of all obtained by the end-inflation occlusion method, describing the effects of molecules of endocrinological interest such as endothelin, erythropoietin and renin-angiotensin, on respiratory mechanics parameters.

Methods: The papers considered in this review were found by inserting in Pubmed/Medline the following indexing terms: hormones, endothelin, erythropoietin, angiotensin and respiratory mechanics.

Biomechanical behavior of human crural fascia in anterior and posterior regions of the lower limb.

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.

Biomechanical behavior of pericardial human tissue: a constitutive formulation.

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.

Investigation of the biomechanical behaviour of articular cartilage in hindfoot joints.

Numerical models represent a powerful tool for investigating the biomechanical behavior of articular cartilages, in particular in the case of complex conformation of anatomical site. In the literature, there are complex non-linear-multiphase models for investigating the mechanical response of articular cartilages, but seldom implemented for the analysis of high organized structure such as the foot. In the present work, the biomechanical behavior of foot cartilage is investigated by means of a fiber-reinforced hyperelastic constitutive model.

Constitutive modeling of time-dependent response of human plantar aponeurosis.

The attention is focused on the viscoelastic behavior of human plantar aponeurosis tissue. At this purpose, stress relaxation tests were developed on samples taken from the plantar aponeurosis of frozen adult donors with age ranging from 67 to 78 years, imposing three levels of strain in the physiological range (4%, 6%, and 8%) and observing stress decay for 240 s. A viscohyperelastic fiber-reinforced constitutive model with transverse isotropy was assumed to describe the time-dependent behavior of the aponeurotic tissue.

Investigation of the mechanical behaviour of the foot skin.

Background/purpose: The aim of this work was to provide computational tools for the characterization of the actual mechanical behaviour of foot skin, accounting for results from experimental testing and histological investigation. Such results show the typical features of skin mechanics, such as anisotropic configuration, almost incompressible behaviour, material and geometrical non linearity. The anisotropic behaviour is mainly determined by the distribution of collagen fibres along specific directions, usually identified as cleavage lines.

Characterization of the anisotropic mechanical behaviour of colonic tissues: experimental activity and constitutive formulation.

The aim was to investigate the biomechanical behaviour of colonic tissues by a coupled experimental and numerical approach. The wall of the colon is composed of different tissue layers. Within each layer, different fibre families are distributed according to specific spatial orientations, which lead to a strongly anisotropic configuration.

Analysis of the biomechanical behaviour of gastrointestinal regions adopting an experimental and computational approach.

An integrated experimental and computational procedure is provided for the evaluation of the biomechanical behaviour that characterizes the pressure-volume response of gastrointestinal regions. The experimental activity pertains to inflation tests performed on specific gastrointestinal conduct segments. Different inflation processes are performed according to progressively increasing volumes.

Constitutive formulations for the mechanical investigation of colonic tissues.

A constitutive framework is provided for the characterization of the mechanical behavior of colonic tissues, as a fundamental tool for the development of numerical models of the colonic structures. The constitutive analysis is performed by a multidisciplinary approach that requires the cooperation between experimental and computational competences. The preliminary investigation pertains to the review of the tissues histology.

Investigation of the biomechanical behaviour of hindfoot ligaments.

The aim of this work is to provide a computational tool for the mechanical characterization of the hindfoot ligaments. The investigation is performed by a coupled numerical and experimental approach. For this purpose, a numerical model that represents the complex structural configuration of the hindfoot and the typical features of the mechanical behaviour of the ligament tissue is developed.

Analysis of heel pad tissues mechanics at the heel strike in bare and shod conditions.

A combined experimental and numerical approach is used to investigate the interaction phenomena occurring between foot and footwear during the heel strike phase of the gait. Two force platforms are utilised to evaluate the ground reaction forces of a subject in bare and shod walking. The reaction forces obtained from the experimental tests are assumed as loading conditions for the numerical analyses using three dimensional models of the heel region and of the running shoe.

Biomechanical behaviour of ankle ligaments: constitutive formulation and numerical modelling.

This study was aimed at the definition of a constitutive formulation of ankle ligaments and of a procedure for the constitutive parameters evaluation, for the biomechanical analysis by means of numerical models. To interpret the typical features of ligaments mechanical response, as anisotropic configuration, geometric non-linearity, non-linear elasticity and time-dependent behaviour, a specific fibre-reinforced visco-hyperelastic model is provided. The identification of constitutive parameters is performed by a stochastic-deterministic procedure that minimises the discrepancy between experimental and computational results.

Investigation on the load-displacement curves of a human healthy heel pad: In vivo compression data compared to numerical results.

The aims of the present work were to build a 3D subject-specific heel pad model based on the anatomy revealed by MR imaging of a subject's heel pad, and to compare the load-displacement responses obtained from this model with those obtained from a compression device used on the subject's heel pad. A 30 year-old European healthy female (mass=54kg, height=165cm) was enrolled in this study. Her left foot underwent both MRI and compression tests.

A numerical model for investigating the mechanics of calcaneal fat pad region.

The present paper pertains to the definition of a numerical model of the calcaneal fat pad region, considering a structure composed of adipose and connective tissues organized in fibrous septae and adipose chambers. The mechanical response is strongly influenced by the structural conformation, as the dimension of adipose chambers, the thickness of connective septae walls and the mechanical properties of the different soft tissues. In order to define the constitutive formulation of adipose tissues, experimental data from pig specimens are considered, according to the functional similarity, while the mechanical response of connective tissue septae is assumed with regard to the mechanical behaviour that characterize ligaments.

Investigation of the mechanical properties of the plantar aponeurosis.

Introduction: The aim of this work was to obtain a preliminary investigation of the mechanical properties of the human plantar aponeurosis based on regional observation, in order to rationally plan a subsequent larger experimental campaign and develop suited constitutive models to characterize the mechanical response of this tissue.

Materials And Methods: Different in vitro mechanical tests were developed on eleven samples taken from the plantar aponeurosis of human cadaver (man, age 78 years). The samples were tested along the distal-proximal direction.

Biomechanical behaviour of heel pad tissue: experimental testing, constitutive formulation, and numerical modelling.

This paper deals with the constitutive formulation of heel pad tissue and presents a procedure for identifying constitutive parameters using experimental data, with the aim of developing a computational approach for investigating the actual biomechanical response. The preliminary definition of constitutive parameters was developed using a visco-hyperelastic formulation, considering experimental data from in vitro compression tests on specimens of fat pad tissue and data from in vivo tests to identify the actual trend of tissue stiffness. The discrepancy between model results and experimental data was evaluated on the basis of a specific cost function, adopting a stochastic/deterministic procedure.

Constitutive modeling of the non-linear visco-elasticity of the periodontal ligament.

A non-linear visco-elastic constitutive model is adopted to describe the relaxation phenomena of the periodontal ligament (PDL). The introduction of a non-linear formulation of visco-elasticity is necessary because experimental data from the literature referring to animal models show that the relaxation rate depends on the level of strain applied. In particular, the percentage of relaxation increases with decrease of the applied strain.

Constitutive formulation and numerical analysis of the heel pad region.

The aim of this work is to provide a numerical approach for the investigation of the mechanical behaviour of the heel pad region. A visco-hyperelastic model is formulated with regard to fat pad tissue, while a fibre-reinforced hyperelastic model is considered for the heel skin tissue. Bone components are defined by means of an orthotropic linear elastic model.

Investigation of foot plantar pressure: experimental and numerical analysis.

The analysis of interaction phenomena occurring between the plantar region of the foot and insole was investigated using a combined experimental-numerical approach. Experimental data on the plantar pressure for treadmill walking of a subject were obtained using the Pedar(®) system. The plantar pressure resultant was monitored during walking and adopted to define the loading conditions for a subsequent static numerical analysis.

Modelling of mandible bone properties in the numerical analysis of oral implant biomechanics.

The biomechanical efficiency of oral implants is deeply influenced by mechanical properties of cortical and trabecular bone in the jaw and, in particular, in the peri-implant region. When the mechanical response of the implant-bone system is analysed by means of numerical models, the effective mechanical properties of bone and the possible change as a function of spatial position must be carefully considered. The procedure presented provides for the attribution of the mechanical properties of bone, considered as anisotropic elastic material, as a function of the spatial position making use of Fourier series and polynomial functions.

Constitutive formulation and analysis of heel pad tissues mechanics.

This paper presents a visco-hyperelastic constitutive model developed to describe the biomechanical response of heel pad tissues. The model takes into account the typical features of the mechanical response such as large displacement, strain phenomena, and non-linear elasticity together with time-dependent effects. The constitutive model was formulated, starting from the analysis of the complex structural and micro-structural configuration of the tissues, to evaluate the relationship between tissue histology and mechanical properties.

A constitutive model for the mechanical characterization of the plantar fascia.

A constitutive model is proposed to describe the mechanical behavior of the plantar fascia. The mechanical characterization of the plantar fascia regards the role in the foot biomechanics and it is involved in many alterations of its functional behavior, both of mechanical and nonmechanical origin. The structural conformation of the plantar fascia in its middle part is characterized by the presence of collagen fibers reinforcing the tissue along a preferential orientation, which is that supporting the major loading.

Biomechanical behaviour of oesophageal tissues: material and structural configuration, experimental data and constitutive analysis.

The aim of the present work is to propose an approach to the biomechanical analysis of oesophagus by defining an appropriate constitutive model and the associated constitutive parameters. The configuration of the different tissues and layers that compose the oesophagus shows very complicated internal anatomy, geometry and mechanical properties. The coupling of these tissues adds to the complexity.