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Objective: Degenerative phenomena may affect esophageal motility as a relevant social-health problem. The diagnosis of such disorders is usually performed by the analysis of data from high-resolution manometry (HRM). Inter- and intraobserver variability frequently affects the diagnosis, with potential interpretative and thus therapeutic errors, with unnecessary or worse treatments. This may be avoided with automatic procedures that minimize human intervention in data processing. Methods: In order to support the traditional diagnostic process, an automatic procedure was defined considering a specific physiomechanical model that is able to objectively interpret data from HRM. A training set ( N = 226) of healthy volunteers and pathological subjects was collected in order to define the model parameters distributions of the different groups of subjects, providing a preliminary database. A statistical algorithm was defined for an objective identification of the patient's healthy or pathological condition by comparing patient parameters with the database. Results: A collection of HRMs including subjects of the training set has been built. Statistical relationships between parameters and pathologies have been established leading to a preliminary database. An automatic diagnosis procedure has been developed to compare model parameters of a specific patient with the database. The procedure was able to match the correct diagnosis up to 86% of the analyzed subjects. Conclusion: The success rate of the automatic procedure addresses the suitability of the developed algorithms to provide a valid support to the clinicians for the diagnostic activity. Significance: The objectivity of developed tools increases the reliability of data interpretation and, consequently, patient acceptance.

Bariatric surgery includes a variety of procedures that are performed on obese people and aim at decreasing the intake of food and calories. This goal is usually pursued by reducing stomach capacity and/or absorbing capability. Adjustable gastric banding is the most common and successful operation. In general, bariatric surgical procedures are effective, but are often associated with major complications. Surgical procedure and post-surgical conformation of the stomach are usually defined on clinical and surgical basis only. Instead, the optimal configuration should be identified by analyzing the mechanical functionality of the stomach and the surrounding structures, and the relationship between food intake, nutrient adsorption, mechanical stimulation of stomach wall and feeling of satiety. A novel approach to bariatric surgery is required, integrating competences in the areas of biomechanics, physiology and surgery, based on a strong interaction between engineers and clinicians. Preliminary results from coupled experimental and computational investigations are here reported. The analyses aim to develop computational tools for the investigation of stomach mechanical functionality in pre- and post-surgical conformations.

The infrapatellar adipose body (Hoffa's fat pad, IFP) is situated between the patellar tendon, the femoral condyle and the tibial plateau. The IFP consists of lobules of white adipose tissue delimited by thin connective septa. The actual structural functionality of the IFP is debated and should pertain to a cushioning role in the knee joint, providing to distribute and to damp mechanical stresses during articular activity. The present study is aimed to analyze the correlation between histological configuration and mechanical properties of the IFP, compared to other adipose tissues, partially differentiated by composition and conformation. Histological and ultrastructural methods were exploited to analyze the microscopic anatomies of IFP, knee (KSF) and abdominal (ASF) subcutaneous fat tissues. Numerical micro-models of the different tissues were developed by using histo-morphometric data, as the size of adipose lobules, the thickness of the septa and their composition. Numerical analyses made it possible to evaluate the mechanical functionality of the different fat tissues considering the characteristic loading conditions, as compressive and shear actions. The results pointed out the actual mechanical relevance of IFP and KSF, while ASF exhibited different mechanical properties. Furthermore, the contribution of connective septa and adipose lobules to compressive and shear mechanical behavior was elucidated. This preliminary investigation represents the basis for biomechanical interpretation and the definition of more refined model to be developed on the acquisition of additional histological and morphometric data.

Recent technological advances in esophageal manometry allowed the definition of new classification methods for the diagnosis of disorders of esophageal motility and the implementation of innovative computational tools for the autonomic, reliable and unbiased detection of different disorders. Computational models can be developed aiming to interpret the mechanical behavior and functionality of the gastrointestinal tract and to summarize the results from clinical measurements, as high-resolution manometry pressure plots, into model parameters. A physiological model was here developed to interpret data from esophageal high-resolution manometry. Such model accounts for parameters related to specific physiological properties of the biological structures involved in the peristaltic mechanism. The identification of model parameters was performed by minimizing the discrepancy between clinical data from high-resolution manometry and model results. Clinical data were collected from both healthy volunteers ( n = 35) and patients with different motor disorders, such as achalasia patterns 1 ( n = 13), 2 ( n = 20) and 3 ( n = 5), distal esophageal spasm ( n = 69), esophago-gastric junction outflow obstruction ( n = 25), nutcracker esophagus ( n = 11) and normal motility ( n = 42). The physiological model that was formulated in this work can properly explain high-resolution manometry data, as confirmed by the evaluation of the coefficient of determination R2 = 0.83 − 0.96. The study finally led to identify the statistical distributions of model parameters for each healthy or pathologic conditions considered, addressing the applicability of the achieved results for the implementation of autonomic diagnosis procedures to support the medical staff during the traditional diagnostic process.

NEW FINDINGS 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. 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 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.

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.

A coupled experimental and computational approach is provided for the identification of the structural behaviour of gastrointestinal 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 in-flow, 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.

Aim The aim of this study was to investigate risk factors for anastomotic stenosis in patients operated on for diverticular disease. Histological inflammation and diverticula at the resection margins were also considered. Method Patients' characteristics, the surgical technique and postoperative complications were collected from the medical records. Anastomotic stenoses were evaluated prospectively by rigid sigmoidoscopy during follow-up examination. Histological specimens were examined by a single pathologist who investigated inflammation and diverticula at the resection margins. Twenty patients with anastomotic colorectal stenosis from a single tertiary centre were compared with 24 consecutive patients without stenosis. They were all operated on for diverticular disease over a specified time period. Results Histological inflammation and diverticula were found in 25% and 30% of the resection margins respectively. Univariate analysis showed that age > 71 years (P = 0.0002), female gender (P = 0.0069) and anastomoses located below 12 cm from the anal verge (P = 0.020) were risk factors for stenosis. No correlation was found between anastomotic stenosis and the presence of histological inflammation or diverticula at the resection margins. By multivariate analysis, only age > 71 years was found to be a statistically significant risk factor for stenosis (P = 0.0003, OR = 60.8, 95% CI: 6.4-575.5). Conclusion Anastomotic stenosis is a frequent, long-term complication following surgery for diverticular disease. An analysis demonstrated that age is a risk factor for colorectal stenosis and that histological inflammation and the presence of diverticula near/at the resection margins have no effect on the incidence of stenosis.

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 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.

Endocrinological factors have been recently described to affect respiratory mechanics.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.The papers considered in this review were found by inserting in Pubmed/Medline the following indexing terms: hormones, endothelin, erythropoietin, angiotensin and respiratory mechanics.It was found that the above cited molecules, beside their well known physiological main effects, exhibit influences on respiratory mechanics, most of all on the airflow resistance, which was described to be increased by endothelin and angiotensin, and decreased by erythropoietin.A number of molecules of biological interest exhibit unexpected influences on respiratory mechanics. The clinical effects depend on the consequences of modified inspiratory pressure values the respiratory muscles have to perform for a given breathing pattern.

Aim The aim of the study was to analyse the incidence of benign colorectal anastomotic stenoses in consecutive patients operated on in a single institution and to assess risk factors for their development. Their impact on quality of life was also evaluated. Method Patient characteristics, indications for surgery, surgical technique and postoperative complications were prospectively recorded. Stenosis was evaluated by rectoscopy at regular intervals, and patients were treated only if symptomatic. After at least 6 months following surgery, patients were asked to respond to the Short Form 36-item quality-of-life questionnaire during a telephone interview. Results Of the original 211 patients considered, 195 underwent a follow-up rectoscopy and were included in the study. Benign stenosis were found in 26 (13%), and 19 (73%) symptomatic patients were treated successfully (15 with endoscopic dilatation and four with radial diathermic surgical incisions). Risk factors for anastomotic stenosis according to univariate analysis were female sex, diverticulitis, mechanical anastomosis, and anastomosis located between 8 and 12 cm from the anal verge. The significant risk factors identified by multivariate analysis were diverticulitis (OR 5, P = 0.002) and mechanical anastomosis (OR 9, P = 0.04). The self-perceived quality of life of patients with stenosis was significantly worse compared with controls. Conclusion Since diverticulitis and mechanical anastomosis are risk factors for anastomotic stenosis, surgeons should take this into account when they are considering what type of anastomotic technique to utilize.

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. Each inflation test is performed by a rapid liquid in-flaw, up to a prescribed volume, which is held constant for about 300s to allow the development of relaxation processes. The different tests are interspersed by 600s of rest to allow the recovery of the specimen mechanical condition. A physio-mechanical model is developed to interpret both the elastic behaviour of the sample, as the pressure-volume trend during the rapid liquid in-flaw, and the time-dependent response, as the pressure drop during the relaxation processes. The minimization of discrepancy between experimental data and model results entails the identification of the parameters that characterize the viscoelastic model adopted for the definition of the behaviour of the gastrointestinal regions. The reliability of the procedure is assessed by the characterization of the response of samples from rat small intestine.