Conference Agenda

Pelvic Organ Prolapse (POP) is a prevalent condition among women globally, arising from weakened pelvic floor structures. Traditional surgical treatments frequently utilize synthetic meshes for reinforcement; however, these materials can cause complications such as erosion and chronic pain. Consequently, biodegradable mesh implants have emerged as promising alternatives due to their improved mechanical biocompatibility. This study investigates the mechanical properties of biodegradable polycaprolactone (PCL) meshes through experimental analyses and computational modeling, aiming to enhance their efficacy for POP repair.
The primary objective of the study is to evaluate the mechanical behavior of biodegradable PCL meshes compared to native vaginal tissue. This involves both experimental testing and numerical simulations. A key focus is assessing how different mesh geometries influence mechanical performance and validating computational models to enhance predictive accuracy for future POP repair applications.
In the methodology, biodegradable PCL meshes with quadratic and cross-shaped geometries were fabricated via melt electrowriting (MEW), with a filament thickness of 240 µm. Uniaxial tensile tests and ball burst tests were conducted on these meshes, alongside comparative tests on sow vaginal tissue. Numerical simulations using Abaqus/Explicit software were developed to replicate ball burst tests, allowing an evaluation of tissue-mesh interaction. Validation of these computational models was performed by comparing them with experimental data.
Results from ball burst testing demonstrated that biodegradable PCL meshes increased the maximum force resistance by approximately 14–20% compared to native vaginal tissue alone. Specifically, the cross-shaped mesh significantly outperformed the quadratic mesh, providing enhanced mechanical reinforcement by up to 30%. Numerical simulations closely matched the experimental results, with discrepancies of around 6% for vaginal tissue, 7% for mesh implants alone, and approximately 14% for mesh-reinforced tissue. These computational models effectively predicted mechanical behavior, indicating their potential in reducing the reliance on extensive in vivo testing.
The study concludes that biodegradable PCL meshes present a highly promising alternative to conventional synthetic meshes for POP treatment. Optimized mesh geometries significantly enhance mechanical support, potentially mitigating complications associated with current synthetic implants. Additionally, validated computational models offer a reliable framework for preclinical assessments, decreasing the dependence on animal testing and accelerating the development of future urogynecological implants. Future research should prioritize in vivo studies to evaluate long-term biocompatibility, degradation profiles, and clinical outcomes.

Pelvic organ prolapse (POP) is one of the most common pelvic floor dysfunctions (PFD), described as the protrusion of the pelvic organs through the vaginal walls. Recently, cases have been rising, affecting women's quality of life. Severe cases often require surgical mesh implants, which can cause complications like tissue erosion and infection, leading the FDA to ban transvaginal meshes for POP [1,2]. It is believed that the reported complications are most likely due to insufficient biocompatibility and inappropriate biomechanical properties of these implants [3]. An ideal mesh should be biocompatible, nontoxic, and have antibacterial properties and appropriate mechanical properties. To address this, polycaprolactone (PCL) mesh implants were produced via melt electrowriting (MEW), enabling the printing of complex 3D structures with high resolution at a low cost from melted polymers [4]. After, the meshes were evaluated mechanically and coated with azithromycin, an antibiotic for genitourinary infections.

Uniaxial tensile tests were performed on the meshes, allowing to obtain average stress-strain curves. Then the meshes went through cyclic tests to assess the long-term behavior of the meshes over 100 cycles. Results showed that while all PCL meshes had similar behaviour, those with 1 mm pores sustained higher stress, had a higher resistance to plastic deformation and could endure 19% more stress than the 1.5 mm pore size ones. However, the 1.5 mm pore-size meshes had mechanical properties closer to vaginal tissue but still remain stiffer. Regarding the cyclic tests, the material showed cyclic creep behavior, since the plastic deformation accumulates, and the curves do not go back to the same displacement [5]. It revealed initial damage, with the first cycle causing more damage to the mesh and hardening during plastic deformation. The tensile tests performed after cyclic deformation confirm increased stiffness, as Young’s Modulus rose between 19.2% and 29.3%.

Zone inhibition and biofilm assays evaluated azithromycin’s effectiveness against bacterial infection. Even though FTIR analysis could not confirm antibiotic incorporation, the drug-coated meshes show inhibitory activity against Escherichia coli biofilm formation and Methicillin-susceptible Staphylococcus aureus (MSSA) in its planktonic state. However, it revealed no antimicrobial effect against Methicillin-resistant Staphylococcus aureus (MRSA), which was expected, since MRSA is known as one of the most serious antibiotic-resistant bacteria. Scanning electron microscopy supported these findings. Overall, the results obtained prove that azithromycin incorporation in the PCL meshes was successful, suggesting that MEW-fabricated PCL meshes coated with azithromycin hold promise as improved implants for POP treatment.

This way, drug incorporation allied with meshes with appropriate mechanical characteristics has the potential to obtain a better outcome in surgical mesh implantation for treating POP.

[1] E. Mancuso, C. Downey, E. Doxford‐Hook, M.G. Bryant, P. Culmer, J Biomed Mater Res B Appl Biomater 108 (2020) 771–789.

[2] Food and Drug Administration, (n.d.).

[3] R. Rynkevic, M.E.T. Silva, P. Martins, T. Mascarenhas, J.L. Alves, A.A. Fernandes, Mater Today Commun 32 (2022).

[4] P.D. Dalton, Curr Opin Biomed Eng 2 (2017) 49–57.

[5] A. Głuchowski, W. Sas, Materials 13 (2020) 3907.

The mechanical response of human spinal dura mater under higher strain rates remains incompletely characterized, despite the critical protective role of this fibrous membrane. In the present investigation, samples were harvested from six human donors with a mean age of 79.33 years and prepared in a longitudinal orientation along the spinal axis. Dog-bone-shaped specimens were subjected to uniaxial tensile loading at nominal strain rates of 0.5, 10, and 25 s⁻¹ using a custom-built testing apparatus. Parameters such as elastic modulus, ultimate tensile strength (UTS), and stretch at failure were evaluated potential rate-related effects. Morphometric measurements indicated that posterior specimens exhibited statistically greater thickness and cross-sectional area than anterior ones. However, no definitive increase in mechanical strength was observed on that basis alone.

Strain-rate-dependent stiffening of the dura mater was recorded, with statistically higher elastic modulus values measured at 10 and 25 s⁻¹ relative to 0.5 s⁻¹. At 25 s⁻¹, the mean elastic modulus exceeded 265 MPa, compared to approximately 172 MPa at 0.5 s⁻¹. Ultimate tensile stress values showed overlapping standard deviations but trended toward higher mean levels at 10 s⁻¹. Furthermore, failure stretch appeared slightly lower at 25 s⁻¹, suggesting a reduced ability to sustain elongation under rapid loading conditions. These observations align with previously noted viscoelastic phenomena in other collagenous tissues and underscore the importance of testing spinal dura mater at physiologically and clinically relevant strain rates.

A visco-hyperelastic constitutive framework was used to capture the nonlinear and time-dependent properties of the dura. This approach incorporated transversely isotropic material behavior, reflecting the predominant collagen fiber orientation in the craniocaudal direction, along with rate-dependent viscous terms. Excellent correlations were achieved between the proposed material model and the experimental stress–stretch data across the tested strain rates, as confirmed by high coefficients of determination (adjusted R² > 0.98) and low error metrics.

These results expand the existing knowledge base by characterizing human spinal dura mater at strain rates relevant to high-speed trauma. Inclusion of the derived constitutive model in finite element analyses is anticipated to enhance the biofidelity of human body models, particularly in automotive crashworthiness research or other high-impact applications. In addition, the demonstrated regional geometric differences suggest that more targeted investigations, including biaxial experiments and correlation with tissue microstructure, may further elucidate localized mechanical variations. Overall, the findings highlight the pronounced rate-dependent stiffening of spinal dura mater and contribute essential data for improved simulation of dynamic spinal loading scenarios. Such observations underscore the clinical importance of understanding how rapid loading events may compromise the dural barrier. Further integration of microstructural analyses, including collagen fiber mapping, may clarify the relationship between regional tissue composition and local mechanical outcomes.

Pelvic organ prolapse (POP) is a prevalent condition that significantly impacts the quality of life for women. It occurs when one or more pelvic organs protrude through the vagina, outside the pelvis. Research indicates that up to 50% of women may experience POP at some point in their lives. The risk factors include vaginal childbirth, advancing age, obesity, or increased intra-abdominal pressure [1].

Apical prolapse, particularly affecting the uterus or vaginal vault, is a common form of POP often associated with weakened support structures at the apex, such as the uterosacral ligaments (USLs) and cardinal ligaments (CLs). These ligaments provide structural support, helping maintain the position of distensible organs such as the bladder, vagina, rectum, and uterus.

The number of pelvic floor dysfunctions, including pelvic organ prolapse, is expected to rise, increasing the demand for effective treatments. While synthetic meshes have been widely used, some were banned from the market by the FDA due to safety concerns [2]. Therefore, new tools to improve our understanding of this issue are crucial.

Recent studies on 3D printing have focused on developing biodegradable meshes using Polycaprolactone (PCL), a biocompatible and FDA-approved polyester. PCL degrades within 2–3 years and may hold promise for POP repair surgery, potentially reducing mesh-related complications (MRCs) such as chronic pain.

Proper anchoring and secure suture fixation are essential for preventing post-surgical MRCs. These techniques ensure mesh stability until full tissue integration is achieved. Mesh anchoring failure has been reported in 38% of patients, with an average occurrence of 1.8 years after implantation. Therefore, a comprehensive understanding of the implantation process is crucial for optimizing surgical outcomes.

In the present study, computational models of biodegradable porous mesh implants with square and sinusoidal geometries were developed to mimic the function of the USLs and CLs, which are critical for supporting pelvic organs. These computational implants were integrated into a computational pelvic cavity model to evaluate the superior-inferior displacement of the anterior vaginal wall during the Valsalva maneuver (VM) at different levels of ligaments impairment: 50%, 90%, and 100% (total rupture).

The results showed a baseline supero-inferior displacement of 6.38 mm in the healthy model. For the USLs, a 50% impairment increased displacement to 7.03 mm while a total rupture resulted in a displacement of 10.77 mm. For the CLs, impairment of 50% led to displacements of 6.74 mm while total rupture resulted in a displacement of 8.58 mm.

The integration of computational implant models reduced the anterior vaginal wall displacement across all impairment scenarios. Implants USLs-mimicking with square geometry, restoring up to 9% of displacement in cases of total USLs rupture compared to the asymptomatic model. When impairment was applied simultaneously to both ligament types (CLs and USLs), it was observed that the USLs primarily provide support, whereas the CLs mainly contribute to stabilization.

These findings underscore the promising potential of biodegradable meshes in improving POP repair.

Keywords: pelvic organ prolapse, apical ligaments, biodegradable implants, computational models

[1] Carroll et al.,PloS One,17:e0276788,2022.

[2] Food and Drug Administration,FDA actions on surgical mesh,2019.

1. Introduction

Eye movements are essential for visual integration, from fixational eye movements to saccades. Several studies have shown dependence between eye movements and ocular tissues strain (Demer, 2016). Integration of large eye movements in Finite Element Model (FEM) was previously addressed on simplified geometries (Karimi et al., 2017). Predicting activations parameters within a continuum extra ocular muscle model is a challenge since in-vivo measures are difficult. We propose a FEM that includes sclera, optic nerve and horizontal rectus muscles to implement new range of movements.

2. Methods

We retrieved an Abaqus assembly from a study on the ocular adduction by active extraocular muscle (EOM) contraction (Jafari et al., 2021). We assumed all tissues except the EOMs to be homogeneous, isotropic, incompressible, and hyperelastic based on previous modelisation (Jafari et al., 2021). A user subroutine models muscle contraction via EOM material properties. The quasi-incompressible strain energy density formulation captures both active and passive muscle behaviors (Grasa & Calvo, 2021). Muscle fibers anisotropy is accounted with an active stretch along the muscle fibers.

3. Results and discussion

Based on previous methodologies (Karimi et al., 2017), the model will be validated to reproduce horizontal saccadic movements where tensions in extra-ocular muscles have been quantified. Activations of the rectus muscles for saccadic movements exceeding previous range of motion are established. The principal strains will be quantified for saccadic movements in the peripapillary sclera.

4. Conclusions

Simulations of movements and corresponding activations will be extended through inverse simulations based on movements captured with an eye tracker. Positions implying important strains will be assessed, based on previous quantification of strains in eyes (Demer, 2016; Jafari et al, 2024).

Acknowledgements:

We thank S. Jafari and J. Demer for the Abaqus assembly and the 3D mesh.

Funding:

This project was partially funded by the French National Agency of Research and Technology via the convention Cifre 2023/0280. Several authors are employees of EssilorLuxottica.

References:

Demer, J. L. (2016). Optic Nerve Sheath as a Novel Mechanical Load on the Globe in Ocular Duction. Investigative Opthalmology & Visual Science, 57(4), 1826. doi: 10.1167/iovs.15-18718

Karami, A., Eghtesad, M., & Haghpanah, S. A. (2017). Prediction of muscle activation for an eye movement with finite element modeling. Computers in Biology and Medicine, 89, 368‑378. doi: 10.1016/j.compbiomed.2017.08.018

Jafari, S., Lu, Y., Park, J., & Demer, J. L. (2021). Finite Element Model of Ocular Adduction by Active Extraocular Muscle Contraction. Investigative Opthalmology & Visual Science, 62(1), 1. doi: 10.1167/iovs.62.1.1

Grasa, J., & Calvo, B. (2021). Simulating Extraocular Muscle Dynamics. A Comparison between Dynamic Implicit and Explicit Finite Element Methods. Mathematics, 9(9), 1024. doi: 10.3390/math9091024