Chronic otitis media is often connected to Eustachian tube dysfunction. As successful treatment cannot be guaranteed with the currently available options, the aim is to develop a stent for the Eustachian tube (ET). Over the course of this development, different prototypes were generated and tested in ex vivo experiments. Four different prototypes of an ET stent and one commercially available coronary stent were implanted in the ET of seven human donor bodies. The position of the stents was verified by cone beam CT. The implanted ETs were harvested, embedded in resin and ground at 200 µm steps. Resulting images of the single steps were used to generate 3D models. The 3D models were then evaluated regarding position of the stent in the ET, its diameters, amount of squeezing, orientation of the axes and other parameters. Virtual reconstruction of the implanted ET was successful in all cases and revealed one incorrect stent placement. The cross-section increased for all metal stents in direction from the isthmus towards the pharyngeal orifice of the ET. Depending on the individual design of the metal stents (open or closed design), the shape varied also between different positions along a single stent. In contrast, the cross-section area and shape remained constant along the polymeric prototype. With the current investigation, insight into the behavior of different prototypes of ET stents was gained, which can help in defining the specifications for the intended ET stent.

For the development of stent-based intraluminal prostheses to treat chronic venous insufficiency, comprehensive knowledge of morphometric and mechanical parameters of the femoral veins (FV) is crucial for an optimized implant design. These data is essential as input for material models for numerical simulations of venous valves prostheses. However, data on mechanical properties of native/unfixed FV tissue are scarce. Unfixed native tissue, though, has limited availableness and durability due to progressing decay. To address these challenges, this study aimed to determine stress-strain behavior and compliance from native specimens of the human FV and its valves from body donations and compared the data to chemically fixed material. A large data set has been generated in tensile tests with a total of 313 venous wall and 78 valve leaflet specimens in different fixation groups from a total of 41 body donations. Tensile testing was conducted at cut rectangular specimens in longitudinal as well as circumferential direction of the vein walls and in one specific direction for the valve leaflets. Young's moduli E₁ and E₂ in two differently defined strain regions, tensile strength R_m and elongation at break A were determined. Additionally, compliance measurements were performed at whole, unfixed vein segments using optical coherence tomography to determine the vessel diameter at increasing intravascular pressure from 20 to 240 mmHg. Significant differences were found in the tensile parameters between unfixed tissue and the different fixations (exemplary Young's modulus E₁ in longitudinal direction: E_{1, unfixed} = 5.7 ± 5.1 N/mm², E_{1, FA} = 13.1 ± 11.9 N/mm², E_{1, PFA} = 2.3 ± 1.0 N/mm). A distinct anisotropy of the mechanical properties could only be detected for PFA fixed material when comparing longitudinal and circumferential tensile direction. Resultant mean compliance values over all segments and measuring positions of the vein segments for the analyzed pressure stages were in the range from 18.16 to 3.78 %/100 mmHg and showed a distinct decrease with increasing pressure. Fixation (FA, PFA) alters the elastomechanical behavior, but the parameters were still in a similar order of magnitude considering the naturally occurring variability. Thus, testing of fixed tissue appears to be as appropriate as the use of this material for ex vivo testing. The provided material data of femoral veins (longitudinal and circumferential) as well as venous valve leaflets may serve as basis for numerical models, e.g. for the development of artificial venous valves.

Finite element analysis (FEA) is common in biomedical engineering for combining design and material development, with model validation crucial for accurate prediction of material behavior. Simplified geometries are commonly needed in stent development due to high effort in prototype manufacturing. This study outlines a methodology for FEA validation related to stent development-related FEA validation using injection-molded planar 2D substructures from a stent design with two types of polymers: poly(l-lactide) (PLLA) and poly(glycolide-co-trimethylene carbonate) (PGA-co-TMC). Specimens underwent quasi-static and cyclic testing, including loading, stress relaxation, unloading, and strain recovery. The material model coefficients for FEA were calibrated for three different constitutive models: linear elastic–plastic (LEP), Parallel Rheological Framework (PRF), and Three-Network (TN) model. The validation of planar stent segment expansion (PSSE) showed strong agreement with the experiments in deformation patterns, with varying force–displacement responses. The PRF and TN models provided better fits for behavioral predictions, with the PRF model being especially favorable for PLLA, while all models exhibited limitations for PGA-co-TMC. This study proposes a robust approach for the material modeling in stent development, enabling efficient material screening and stent design optimization through a simplified 2D validation setup. Material model accuracy depends strongly on calibration–load case congruence, while phenomenological approaches (PRF) show enhanced model robustness against load case variations compared to physically coupled models (TN).

To simulate the specific material properties of thermoplastic polymers a suitable constitutive model is essential. The parallel rheological framework (PRF) model was calibrated and evaluated in this study as potential constitutive model for polymer stent application. Tensile as well as recovery tests with different loading rates were performed using PLLA specimens. In order to calibrate the constitutive model, the conducted material tests were simulated accordingly. The parameters of the model were iteratively varied to obtain good accordance of the simulation with the material tests. In contrast to elastic plastic material models, viscoelastic material behavior can be represented with the nonlinear viscoelastic-plastic PRF model. The generated and possibly further refined model can be used for the simulation of polymer stents.