Charakterystyka właściwości biomechanicznych ścian aorty brzusznej

Background. The structure of the aorta wall is well adapted to withstand the mechanical loads caused by arterial blood pressure. The most important structural components of the aortic wall are elastin and collagen fibres. Elastin and collagen fibres allow reversible deformation of, and give mechanical strength to, the aorta. Alterations in composition cause changes in the mechanical properties of the aortic wall. Hence, the main aim of this study is the biomechanical assessment and preliminary histological study of the abdominal aortic wall. Material and methods. Specimens were cut from the materials obtained during autopsies, taking research standards into consideration, which were then examined in order to determine the directional material properties. The second part of the materials was intended for histological analysis. Results. It was appreciable that the mechanical strength of the aortic wall is higher in the transversal than in the longitudinal direction, which has a vital meaning for the correct functioning of the organism, and it makes the vessel able to perform reversible deformation under the influence of pulsatile blood pressure. This ability is strongly dependent on the structural composition of the aortic wall. Conclusions. Structural alterations due to atherosclerotic lesions of various degrees lead to a significant increase of stiffness and decrease of mechanical strength of the walls of abdominal aorta.Wstęp. Struktura ścian aorty jest przystosowana do stawiania oporu mechanicznym obciążeniom, które wywoływane są przez ciśnienie tętnicze. Najważniejszymi elementami strukturalnymi ścian aorty są włókna elastynowe i kolagenowe. Odpowiadają one za odwracalne odkształcanie się ścian aorty oraz ich mechaniczną wytrzymałość. Dlatego też głównym celem tej pracy jest ocena biomechaniczna oraz analiza histologiczna ścian aorty brzusznej. Materiał i metody. Z materiału pobranego podczas sekcji zwłok wycinano próbki w celu określenia właściwości mechanicznych ścian aorty brzusznej. Pozostałą część materiału przeznaczono do analiz histologicznych. Wyniki. Odnotowano, że mechaniczna wytrzymałość ścian aorty jest większa w kierunku obwodowym niż wzdłużnym. Cecha ta ma kluczowe znaczenie dla poprawnego funkcjonowania organizmu dzięki zdolności naczynia do odwracalnego odkształcania się pod wpływem tętniczego przepływu krwi w naczyniu. Zdolność ta silnie zależy od struktury naczynia. Wnioski. Zmiany strukturalne spowodowane przez miażdżycę prowadzą do znaczącego wzrostu sztywności i obniżenia wytrzymałości mechanicznej ścian aorty brzusznej

Material characteristic of an innovative stent for the treatment of urethral stenosis

The appropriate development and customisation of the stent to the urethral tissues requires the determination of many factors such as strength and degradation. Given the distinctive conditions of urethral tissues, it is important that the design of the stent be properly developed. The selection of a stent material requires knowing its material characteristics and verifying that they are suitable for the future implantation site. In the present study, the development of a polydioxanone (PDO)-based stent was undertaken. The PDO material was fabricated using an additive technique – 3D printing. Then, in vitro tests were performed to determine the degradation time of the material under conditions simulating an aggressive urinary environment. The changes in the parameters of mechanical properties before and after the degradation period were determined, and the changes in the structure of the material before and after degradation were observed. Numerical analysis was performed for the proposed stent design. The results showed that PDO has good mechanical properties, but its degradation time is too short to be used in a urethral stent. Among the innovations of the studies conducted are bending strength tests, which is not a frequently considered aspect so far

Evaluation of Selected Properties of Sodium Alginate-Based Hydrogel Material—Mechanical Strength, μDIC Analysis and Degradation

The search for ideal solutions for the treatment of urethral stenosis continues. This includes developing the material, design, while maintaining its optimal and desired properties. This paper presents the results of the research conducted on sodium alginate-based hydrogel material (AHM), which may be used as a material for stents dedicated to the treatment of pathologies occurring in the genitourinary system. In order to determine the selected parameters of the AHM samples, strength and degradation tests, as well as analysis of the micro changes occurring on the surface of the material using a digital image correlation (µDIC) system, were performed. This study shows that the material possessed good mechanical strength parameters, the knowledge of which is particularly important from the point of view of the stent-tissue interaction. The degradation analysis performed showed that the AHM samples degrade in an artificial urine environment, and that the degradation time mainly depends on the chemical composition of the material. The novel µDIC method performed allowed us to characterize the homogeneity of the material structure depending on the cross-linking agent used

Material and Structural Modeling Aspects of Brain Tissue Deformation under Dynamic Loads

The aim of this work was to assess the numerous approaches to structural and material modeling of brain tissue under dynamic loading conditions. The current technological improvements in material modeling have led to various approaches described in the literature. However, the methods used for the determination of the brain’s characteristics have not always been stated or clearly defined and material data are even more scattered. Thus, the research described in this paper explicitly underlines directions for the development of numerical brain models. An important element of this research is the development of a numerical model of the brain based on medical imaging methods. This approach allowed the authors to assess the changes in the mechanical and geometrical parameters of brain tissue caused by the impact of mechanical loads. The developed model was verified through comparison with experimental studies on post-mortem human subjects described in the literature, as well as through numerical tests. Based on the current research, the authors identified important aspects of the modeling of brain tissue that influence the assessment of the actual biomechanical response of the brain for dynamic analyses

Numerical Analyses of Fracture Mechanism of the Pelvic Ring during Side-Impact Load

The aim of this study is the analysis of the multiple pelvis fracture mechanism in side-impact dynamic load cases. The elaborated numerical model of a pelvis complex includes pelvic and sacral bones as well as soft tissues such as ligaments and cartilages. The bone has been modelled as a viscoelasticity material based on the Johnson–Cook model. The model parameters have been chosen based on the experimental data. The uniqueness of a presented approach refers to the selection of crack criteria for the bone. Thus, it was allowed to analyse the process of multiple fractures inside the pelvic bones. The analysis was evaluated for the model in which the deformation rate influences the bone material properties. As a result, the stress distributions inside particular bones were changed. It has been estimated that the results can vary by 50% or even more depending on the type of boundary conditions adopted. The second step of work was a numerical analysis of military vehicle subjected to an IED. An analysis of the impactor’s impact on the pelvis of the Hybrid ES-2RE mannequin was conducted. It was shown that the force in the pelvis exceeds the critical value by a factor of 10. The results of the numerical analysis were then used to validate the model of a military vehicle with a soldier. It was shown that for the adopted loading conditions, the critical value of the force in the pelvis was not exceeded

Biomechanical testing of trachea in a multidirectional load state

Uszkodzenia tchawicy spowodowane wprowadzeniem rur umożliwiających przywrócenie wentylacji płuc. Identyfikacja parametrów mechanicznych jest konieczna w celu rozpoznania patomechanizmu zmian w tkance, związanych z nieprawidłową przebudową. Uzyskane rezultaty badań mechanicznych pozwoliły na opracowanie modelu matematycznego tchawicy w warunkach wielokierunkowego obciążenia. Umożliwi to przewidywanie nadmiernych lokalnych zaburzeń pól odkształceń i naprężeń tchawicy, występujących podczas wprowadzenia rurki intubacyjnej, które do tej pory nie zostały jeszcze dokładnie zbadane.Tracheal injury caused by the introduction of tubes to restore lung ventilation. Identification of mechanical parameters is necessary in order to identify changes in the pathomechanism of tissue associated with abnormal remodeling. The results of mechanical tests allowed us to develop a mathematical model of the trachea in a multidirectional load conditions. This will allow prediction of excessive local disturbances of the fields of strain and stress in the trachea wall occurring during the insertion of the tracheal tube, which so far have not yet been thoroughly investigated

Changes in the Mechanical Properties of Alginate-Gelatin Hydrogels with the Addition of Pygeum africanum with Potential Application in Urology

New hydrogel materials developed to improve soft tissue healing are an alternative for medical applications, such as tissue regeneration or enhancing the biotolerance effect in the tissue-implant–body fluid system. The biggest advantages of hydrogel materials are the presence of a large amount of water and a polymeric structure that corresponds to the extracellular matrix, which allows to create healing conditions similar to physiological ones. The present work deals with the change in mechanical properties of sodium alginate mixed with gelatin containing Pygeum africanum. The work primarily concentrates on the evaluation of the mechanical properties of the hydrogel materials produced by the sol–gel method. The antimicrobial activity of the hydrogels was investigated based on the population growth dynamics of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, as well as the degree of degradation after contact with urine using an innovative method with a urine flow simulation stand. On the basis of mechanical tests, it was found that sodium alginate-based hydrogels with gelatin showed weaker mechanical properties than without the additive. In addition, gelatin accelerates the degradation process of the produced hydrogel materials. Antimicrobial studies have shown that the presence of African plum bark extract in the hydrogel enhances the inhibitory effect on Gram-positive and Gram-negative bacteria. The research topic was considered due to the increased demand from patients for medical devices to promote healing of urethral epithelial injuries in order to prevent the formation of urethral strictures