Revealing The True Mechanical Behavior Of Porous Tendon Scaffolds Via In Situ Morphometry

This study examines how strain-driven changes in volume fraction and geometry influence the mechanics of porous scaffolds, aiming to improve the accuracy of their stress–strain description. Single bundles and hierarchical structures (8 bundles surrounded by a membrane), made of poly(L-lactic) acid and collagen type I, were electrospun as tendon/ligament scaffolds and examined via In Situ tensile tests in micro-CT. This enabled the development of a framework to compare stress metrics with increasing complexity. Apparent and net stress were obtained from the initial samples’ cross-sections and material volume fractions. Micro-CT revealed strain-dependent morphological changes, allowing computation of actual stress–strain behavior. Scaffolds’ nanofibers orientation/cross-section were quantified via SEM. The mechanical interpretation changed significantly when using strain-dependent morphometry (actual stress–strain) rather than the initial, static geometry (apparent stress–strain). Bundles’ actual elastic modulus was statistically higher than hierarchical structures’ one due to membrane-bundle and inter-bundle interactions. The different stress definitions yield varying levels of accuracy depending on the experimental complexity. Stress models are provided, allowing a compromise between characterization reliability and experimental complexity. Morphological evolution during deformation strongly affects mechanical response: at the tissue scale, it improves comparison between scaffold and native tissue behavior; at the cellular scale, it predicts the substrate stiffness sensed by cells.