Conference Agenda

Pelvic organ prolapse (POP) is a condition that significantly impacts the quality of life for many women and is characterised by the descent of pelvic organs. Initially, synthetic polypropylene meshes were introduced for POP repair due to their high success rates in correcting abdominal hernias. However, the Food and Drug Administration (FDA) later banned the commercialisation of these meshes, highlighting the urgent need for alternative approaches [1]. This study aims to develop biodegradable meshes as an alternative solution for POP repair. Biodegradable meshes offer promising biocompatibility and biomechanical properties, making them a potential solution to the limitations of synthetic meshes.

Computational models were utilised to design meshes with variations in pore geometry, pore size, filament thickness, and filament placement in specific regions. To validate the simulation results, meshes were 3D printed, and uniaxial tensile tests were conducted using the sow's vaginal tissue. The results were compared with simulations to identify meshes exhibiting behaviour similar to vaginal tissue. Additionally, outcomes were compared with the properties of the uterosacral ligament and a commercially available mesh [2].

The mesh featuring a smaller pore diameter (1.50 mm), strategically placed filaments, and variable filament thickness most closely replicated the behaviour of vaginal tissue. However, none of the tested meshes exhibited behaviour comparable to the uterosacral ligament. The findings also suggest that the commercially available mesh may not be the optimal treatment option, as it does not accurately represent the behaviour of either vaginal tissue or the uterosacral ligament [2].

With these findings, a new concept emerged, developing meshes using different materials with varying degradation periods, such as polylactic acid (PLA) and polycaprolactone (PCL). Given the distinct behaviours of these materials, it would be interesting to develop meshes using both materials with the previously designed geometries. By varying the proportions of PLA and PCL, it will be possible to create meshes that closely mimic the behaviour of vaginal tissue and ligaments. Preliminary studies indicate a decrease in Young's modulus, suggesting promising potential for mesh development. In this initial test, meshes with square pores were developed using filaments composed of 96% PLA and 4% medical-grade PCL to assess the material behavior, yielding a Young's modulus of approximately 40 MPa. Investigating the interaction between these materials and their impact on overall biomechanical performance may lead to innovative solutions for more effective, patient-specific POP repairs.

REFERENCES

[1] FDA, “FDA takes action to protect women’s health, orders manufacturers of surgical mesh intended for transvaginal repair of pelvic organ prolapse to stop selling all devices,” https://www.fda.gov/news-events/press-announcements/fda-takes-action-protect-womens-health-orders-manufacturers-surgical-mesh-intended-transvaginal.

[2] M. F. R. R. Vaz, M. E. Silva, M. Parente, S. Brandão, and A. A. Fernandes, “3D printing and development of computational models of biodegradable meshes for pelvic organ prolapse,” Engineering Computations (Swansea, Wales), vol. 41, no. 6, pp. 1399–1423, Aug. 2024, doi: 10.1108/EC-12-2023-0967.

Understanding the mechanical properties of the spinal dura mater is essential for accurate computational modeling of the spinal cord complex. Despite its importance, characterizing this membrane poses unique challenges due to its high anisotropy, thin geometry, and sensitivity to various experimental conditions. This study present a comprehensive evaluation of how measurement technique selection and test protocols - specifically, digital image correlation (DIC) and paint application for speckle generation, crosshead displacement tracking, and preconditioning - impact the resulting mechanical parameters of human spinal dura mater.

In this experiment, spinal dura mater was collected from human donors, from which standardized samples were cut in both longitudinal and transverse orientations. Some of the specimens were coated with a high-contrast paint to enable DIC, while the remaining ones were measured conventionally, based on the crosshead displacement of a universal testing machine. In addition, selected specimens underwent preliminary cyclic loading (preconditioning). The stress in the samples was expressed in terms of I Piola-Kirchhoff stress (PK1) relative to the stretch ratio, and the results were statistically analyzed with consideration of potential demographic and anthropometric factors. Poisson’s ratio was determined from the ratio of the Hencky (logarithmic) strain measured in the transverse direction to that in the longitudinal direction.

Comparisons between crosshead displacement and DIC revealed that the choice of measurement approach significantly influences the extracted mechanical parameters. For longitudinal specimens measured by DIC, elastic moduli were up to 70% higher than values derived from crosshead data, while ultimate strain was up to 35% lower. Further, paint application itself altered tissue behavior, particularly affecting stiffness. In contrast, preconditioning did not emerge as a strong factor in modifying the stress-stretch results. After applying correction factors for these effects, we obtained averaged values for longitudinal extension of approximately 282 MPa (elastic modulus), 25 MPa (failure stress), and 1.10 (failure stretch). In the transverse orientation, these parameters were around 15.6 MPa, 1.56 MPa, and 1.12, respectively.
Notably, Poisson’s ratios ranged from about 2.6 to 4.3, underscoring the tissue’s anisotropic and potentially volume-altering behavior under load.

The findings highlight the necessity of carefully standardizing experimental protocols for testing anisotropic tissues like spinal dura mater. Methodological choices - particularly regarding strain tracking (DIC vs. crosshead), sample preparation, and paint application - can significantly influence stiffness and ultimate strain measurements. These results provide input parameters and correction guidelines for computational models, aiding in the development of more reliable simulations of spinal biomechanics.

Introduction

Dynamic elastography is a fundamental technique to study the local mechanical property of the tissues, such as cornea. It is based on in-vivo tracking of shear waves propagation as a result of a transient stimulation. In quasi-incompressible materials, as the cornea, the shear waves are 150 times slower than the compressional waves. The quasi-incompressible behavior and the double-scale of the phenomena make the FE approximation difficult. We used an efficient scheme to obtain a reliable modelling of transient elastography measurements in incompressible pre-loaded tissues, and we applied to the cornea to reproduce a typical dynamic elastography experiment, on cornea with and without defects.

Method

Wave propagation in cornea can be treated as a linear perturbation of an already loaded material, under the assumption that the wave amplitude is small. The specificity of the biological tissues is the complexity of their mechanical response of tissue, which is almost incompressible, hyperelastic and anisotropic.

We performed a linearization of the elastic problem around the prestressed state. The linearized rigidity has then 2 components: a material one, due to the non-linearity of the constitutive law, and a geometric one, associated with the prestress. For the material constitutive law, we used a microsphere model including the contributions of the isotropic matrix, the collagen lamellae and the quasi-incompressibility of the tissue (Giraudet et al. 2022).

The simulations were done using a mesh reproducing the geometry of the cornea (Pandolfi et al. 2008). The static non-linear problem is solved through a classical iterative method. The wave propagation simulation presents a challenge due to the quasi-incompressible behavior: the time-step is controlled by the velocity of the fastest wave, the compression one, while we are interested in the slow, shear, waves. To overcome this difficulty, we use a fully explicit numerical method (Merlini et al. 2025), based on high-order spectral elements, mass-lumping together with Gauss-Lobatto quadrature rule and an inf-sup stable mixed formulation, and a relaxation of the CFL condition through the use of Chebyshev polynomials.

Results

We observe that the fibers have a limited effect on the main wave velocity, despite the increase of stiffness in the cornea. This may be due to our approximation with they are mainly in-plane, which is consistent with cornea observations, even if some out-of-plane orientations are reported (Petsche et al. 2013). However, they impact significantly a faster wave, with a much lower amplitude.

The IOP and the associated prestress has a significant impact on the velocity of the main wave: the wave is faster on a cornea under pressure than in a cornea in which the IOP has been suppressed.

The introduction of a mechanical defect leads to a significant alteration of the shape of the wave front, indicating that this method can be used for the early detections of pathologies such as keratoconus.

References

- C. Giraudet et al., JMBBM, 129:105121, 2022.

- A. Pandolfi et al., J Biomech Eng, 130: 061006, 2008.

- G. Merlini et al., Waves, submitted 2024.

- S. Petsche et al., BMMB, 12:1101–1113, 2013

Hernia is a physiological condition that significantly impacts patients’ quality of life, where there is an organ prolapse through the wall of the cavity that is normally contained, due to a weakness or opening, mainly of the abdominal wall. Surgical treatment for hernias often involves the use of specialized meshes to support the abdominal wall. While this method is highly effective, it frequently leads to complications such as pain, infections, inflammation, adhesions, and even the need for revision surgeries. According to the Food and Drug Administration (FDA), hernia recurrence rates can reach up to 11%, surgical site infections occur in up to 21% of cases, and chronic pain incidence ranges from 0.3% to 68%. These statistics highlight the urgent need to improve mesh technologies to minimize such complications.
In this study, a preliminary innovative melt-electrowritten mesh with antistatic properties from hernia repair is presented. Melt Electrowriting is a promising technique, which allows a precise deposition of thin fibers, mimicking the fibrillar component of the native extracellular matrix. The study investigated the effect of incorporating the antistatic agent Hostastat ® FA 38 (HT) at concentrations of 0.03, 0.06, and 0.1 wt% on the fiber diameter and mechanical properties of Polycaprolactone (PCL) meshes. The addition of HT reduced fiber diameter by 14–17%, 39–45%, and 65–66%, depending on the mesh geometry (square or sinusoidal, both with a 1.5 mm pore size). The reduced fiber diameter correlated with increased tensile strength and Young’s Modulus, as verified through uniaxial tensile testing. Comparisons between PCL/HT and pure PCL meshes with similar diameters and geometries confirmed the enhanced mechanical properties of PCL/HT meshes. Cytotoxicity tests, using the resazurin assay, indicated no cytotoxic effects at any HT concentration. Both sterilization methods (Ethanol + UV and UV only) showed no significant differences in results. These findings demonstrate that incorporating HT into PCL meshes produces thinner, more stable filaments with improved mechanical performance and no cytotoxicity, making them a promising material for applications such as hernia repair. Future studies on polymer-additive interactions could further optimize their mechanical and biological properties.

Keywords: Hernia Repair; Biodegradable Mesh Implants; Melt Electrowriting; Antistatic Agent; Cytotoxicity

Biodegradable magnesium (Mg) implants offer an attractive alternative to permanent metallic devices by gradually dissolving as natural bone regenerates, thereby reducing long‐term complications. However, predicting the degradation behavior of Mg and its interaction with surrounding tissues remains a significant challenge. In our work, we present a novel multiscale computational framework that couples a nonlocal peridynamic corrosion model with a bone healing and remodeling model. The peridynamic model accurately captures the time-dependent degradation of Mg by simulating its progressive dissolution and macroscopic volume loss, while dynamically linking the release of Mg ions to local biological responses. This ion release directly influences osteoblast differentiation and subsequent mineralization of the bone matrix, providing new insights into the connection between implant degradation and tissue regeneration. While our primary focus is on quantifying the biocorrosion of Mg and its immediate impact on bone healing, our framework also lays the groundwork for future integration of soft tissue biomechanics to further enhance implant-tissue integration. This coupled model serves as a robust tool for designing next-generation biodegradable implants and optimizing their mechanical performance and biocompatibility. Our findings promise to advance implant design strategies by linking degradation kinetics with tissue growth, thereby facilitating a more predictive and personalized approach to clinical treatment and opening avenues for interdisciplinary research in biomechanics and regenerative medicine.