Open Access
Computational analysis of polymeric biodegradable and customizable airway stent designs
(MDPI, 2024-06-14) Ayechu Abendaño, Ada; Pérez-Jiménez, Aurora; Sánchez-Matás, Carmen; López-Villalobos, José Luis; Díaz Jiménez, Cristina; Fernández-Parra, Rocío; Malvè, Mauro; Ingeniería; Ingeniaritza
The placement of endotracheal prostheses is a procedure used to treat tracheal lesions when no other surgical options are available. Unfortunately, this technique remains controversial. Both silicon and metallic stents are used with unpredictable success rates, as they have advantages but also disadvantages. Typical side effects include restenosis due to epithelial hyperplasia, obstruction and granuloma formation. Repeat interventions are often required. Biodegradable stents are promising in the field of cardiovascular biomechanics but are not yet approved for use in the respiratory system. The aim of the present study is to summarize important information and to evaluate the role of different geometrical features for the fabrication of a new tracheo-bronchial prosthesis prototype, which should be biodegradable, adaptable to the patient’s lesion and producible by 3D printing. A parametric design and subsequent computational analysis using the finite element method is carried out. Two different stent designs are parameterized and analyzed. The biodegradable material chosen for simulations is polylactic acid. Experimental tests are conducted for assessing its mechanical properties. The role of the key design parameters on the radial force of the biodegradable prosthesis is investigated. The computational results allow us to elucidate the role of the pitch angle, the wire thickness and the number of cells or units, among other parameters, on the radial force. This work may be useful for the design of ad hoc airway stents according to the patient and type of lesion.
Open Access
Topological features dictate the mechanics of the mammalian brains
(Elsevier, 2020) Sáez, Pablo; Duñó, C.; Sun, L.Y.; Antonovaite, N.; Malvè, Mauro; Tost, D.; Goriely, A.; Ingeniería; Ingeniaritza
Understanding brain mechanics is crucial in the study of pathologies involving brain deformations such as tumor, strokes, or in traumatic brain injury. Apart from the intrinsic mechanical properties of the brain tissue, the topology and geometry of the mammalian brains are particularly important for its mechanical response. We use computational methods in combination with geometric models to understand the role of these features. We find that the geometric quantifiers such as the gyrification index play a fundamental role in the overall mechanical response of the brain. We further demonstrate that topological diversity in brain models is more important than differences in mechanical properties: Topological differences modify not only the stresses and strains in the brain but also its spatial distribution. Therefore, computational brain models should always include detailed geometric information to generate accurate mechanical predictions. These results suggest that mammalian brain gyrification acts as a damping system to reduce mechanical damage in large-mass brain mammals. Our results are relevant in several areas of science and engineering related to brain mechanics, including the study of tumor growth, the understanding of brain folding, and the analysis of traumatic brain injuries.
Open Access
A parametric tool for studying a new tracheobronchial silicone stent prototype: toward a customized 3d printable prosthesis
(MDPI, 2021) Zurita Gabasa, Jesús; Díaz Jiménez, Cristina; López-Villalobos, José Luis; Malvè, Mauro; Ingeniería; Ingeniaritza
The management of complex airway disorders is challenging, as the airway stent placement usually results in several complications. Tissue reaction to the foreign body, poor mechanical properties and inadequate fit of the stent in the airway are some of the reported problems. For this reason, the design of customized biomedical devices to improve the accuracy of the clinical results has recently gained interest. The aim of the present study is to introduce a parametric tool for the design of a new tracheo-bronchial stent that could be capable of improving some of the performances of the commercial devices. The proposed methodology is based on the computer aided design software and on the finite element modeling. The computational results are validated by a parallel experimental work that includes the production of selected stent configurations using the 3D printing technology and their compressive test.
Open Access
On studying the interaction between different stent models and rabbit tracheal tissue: numerical, endoscopic and histological comparison
(Biomedical Engineering Society, 2016) Chaure, J.; Serrano, C.; Fernández-Parra, Rocío; Peña, Estefanía; Malvè, Mauro; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
Stenting technique is employed worldwide for treating atherosclerotic vessel and tracheal stenosis. Both diseases can be treated by means of metallic stents which present advantages but are affected by the main problem of restenosis of the stented area. In this study we have built a rabbit trachea numerical model and we have analyzed it before and after insertion and opening of two types of commercial stent: a Zilver® FlexTM Stent and a WallStentTM. In experimental parallel work, two types of stent were implanted in 30 New Zealand rabbits divided in two groups of 10 animals corresponding to each stent type and a third group made up of 10 animals without stent. The tracheal wall response was assessed by means of computerized tomography by endoscopy, macroscopic findings and histopathological study 90 days after stent deployment. Three idealized trachea models, one model for each group, were created in order to perform the computational study. The animal model was used to validate the numerical findings and to attempt to find qualitative correlations between numerical and experimental results. Experimental findings such as inflammation, granuloma and abnormal tissue growth, assessed from histomorphometric analyses were compared with derived numerical parameters such as wall shear stress (WSS) and maximum principal stress. The direct comparison of these parameters and the biological response supports the hypothesis that WSS and tensile stresses may lead to a greater tracheal epithelium response within the stented region, with the latter seeming to have the dominant role. This study may be helpful for improving stent design and demonstrates the feasibility offered by in-silico investigated tracheal structural and fluid dynamics.

Malvè, Mauro

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