CSS has shown to be a reliable method to assess the skin lesions in patients with LS. It is reproducible, easy to use and, with the support of the CSS software, applicable worldwide.

New Findings r What is the central question of this study?Prostheses for treatment of urinary incontinence elicit complications associated with an inadequate mechanical action. This investigation aimed to define a procedure addressed to urethral mechanical characterization. Experimental tests are the basis for constitutive formulation, with a view to numerical modelling for investigation of the interaction between the tissues and a prosthesis. r What is the main finding and its importance?Horse urethra, selected for its histomorphometric similarity to human urethra, was characterized by integrated histological analysis and mechanical tests on the biological tissue and structure, leading to constitutive formulation. A non-linear, anisotropic and time-dependent response was found, representing a valid basis for development of a numerical model to interpret the functional behaviour of the urethra.Urinary dysfunction can lead to incontinence, with an impact on the quality of life. Severe dysfunction can be overcome surgically by the use of an artificial urinary sphincter. Nonetheless, several complications may result from inappropriate functioning of the prosthesis, in many instances resulting from an unsuitable mechanical action of the device on the urethral tissues. Computational models allow investigation of the mechanical interaction between biological tissues and biomedical devices, representing a potential support for surgical practice and prosthesis design. The development of such computational tools requires experimental data on the mechanics of biological tissues and structures, which are rarely reported in the literature. The aim of this study was to provide a procedure for the mechanical characterization of urethral tissues and structures. The experimental protocol included the morphometric and histological analysis of urethral tissues, the mechanical characterization of the response of tissues to tensile and stress-relaxation tests and evaluation of the behaviour of urethral structures by inflation tests. Results from the preliminary experiments were processed, adopting specific model formulations, and also providing the definition of parameters that characterize the elastic and A. N. Natali and others viscous behaviour of the tissues. Different experimental protocols, leading to a comprehensive set of experimental data, allow for a reciprocal assessment of reliability of the investigation approach.

Urinary incontinence, often related to sphincter damage, is found in male patients, leading to a miserable quality of life and to huge costs for the healthcare system. The most effective surgical solution currently considered for men is the artificial urinary sphincter that exerts a pressure field on the urethra, occluding the duct. The evaluation of this device is currently based on clinical and surgical competences. The artificial sphincter design and mechanical action can be investigated by a biomechanical model of the urethra under occlusion, evaluating the interaction between tissues and prosthesis. A specific computational approach to urethral mechanics is here proposed, recalling the results of previous biomechanical experimental investigation. In this preliminary analysis, the horse urethra is considered, in the light of a significant correlation with human and in consideration of the relevant difficulty to get to human samples, which anyway represents the future advance. Histological data processing allow for the definition of a virtual and a subsequent finite element model of a urethral section. A specific hyperelastic formulation is developed to characterize the nonlinear mechanical behavior. The inverse analysis of tensile tests on urethra samples leads to the definition of preliminary constitutive parameters. The parameters are further refined by the computational analysis of inflation tests carried out on the entire urethral structure. The results obtained represent, in the light of the correlation reported, a valid preliminary support for the information to be assumed for prosthesis design, integrating surgical and biomechanical competences.

The Infrapatellar Fat Pad (IFP) lies between patella, femur, meniscus and tibia and properly fills the space between these structures. This fatty structure facilitates distribution of synovial fluid and may act to absorb impulsive actions generated through the joint. In case of Osteoarthritis (OA), IFP is found to be affected by inflammation, hypertrophy and fibrosis. The aim of the present study is to analyze the correlation between microscopic characteristics and mechanical properties of the IFP in healthy and OA conditions. The microscopic anatomy of the IFP was analyzed through histological methods, whose results showed that the IFP affected by OA maintains similar lobules configuration but thicker interlobular septa. Geometrical data together with the morphological analysis of lobules and septa represented the basic data to provide numerical micro-models of the IFP. Numerical analyses were developed to evaluate the mechanical behavior considering the characteristic loading conditions as compressive, torsion and shear actions. The results were applied to identify the parameters of a homogenized hyperelastic constitutive formulation that interprets the IFP mechanics. The constitutive formulation was implemented within a finite element model of the knee, which was applied to evaluate the overall mechanical functionality of the knee structures. The results pointed out the actual mechanical relevance of IFP and the loss of proper stress-strain behavior of the OA IFP under mechanical loads.

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New Findings r What is the central question of this study?The wall of the colon shows an anisotropic and non-linear mechanical response, because of the distribution and mechanical properties of sub-components. This study aimed to provide, by a coupled experimental and computational approach, a constitutive framework to interpret the mechanics of colonic tissues. r What is the main finding and its importance?Tensile tests on tissue samples from pig colon were developed. The experimental data were processed to define proper constitutive formulations. Constitutive parameters were identified by the inverse analysis of experimental tests. The reliability of parameters was assessed by agreement between the experimental and model results and the satisfaction of material thermomechanics principles. The developed constitutive framework is capable of interpreting the general anisotropic and non-linear mechanical behaviour of colonic tissues.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. Accounting for the complex histology of the tissues, mechanical tests must be planned and designed to evaluate the behaviour of the colonic wall in different directions. Uni-axial tensile tests were performed on tissue specimens from 15 fresh pig colons, accounting for six different loading directions (five specimens for each loading direction). The next step of the investigation was to define an appropriate constitutive framework and develop a procedure for identification of the constitutive parameters. A specific hyperelastic formulation was developed that accounted for the multilayered conformation of the colonic wall and the fibre-reinforced configuration of the tissues. The parameters were identified by inverse analyses of the mechanical tests. The comparison of model results with experimental data, together with the evaluation of satisfaction of material thermomechanics principles, confirmed the reliability of the analysis developed. This work forms the basis for more comprehensive activities that aim to provide computational tools for the interpretation of surgical procedures that involve the gastrointestinal tract, considering the specific biomedical devices adopted.

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