Cyclic tensile behavior of warp-knitted surgical meshes in view of loading direction

Abstract

Surgical mesh used in hernia repair is subjected to repetitive cyclic loading during daily activities. Changes in mechanical properties induced by cyclic loading may reduce mesh performance and contribute to patient discomfort or hernia recurrence. Therefore, these meshes require robust mechanical performance under physiological loading conditions, yet the influence of mesh structural architecture on cyclic tensile behavior and anisotropy remains insufficiently understood. This study investigated the influence of loading direction (course, 45° diagonal, and wale, where the course and wale directions correspond to the principal horizontal and vertical directions of the knitted structure) on the static and cyclic tensile behavior of polypropylene surgical meshes with five different structures (Tricot, pin-hole-net, Sandfly, quasi-Sandfly, and quasi-Marqussite). Static testing revealed pronounced anisotropy in all meshes, with elastic modulus values strongly dependent on the orientation of underlaps, chain loops, and inlay yarns. Under cyclic loading, stretching work, energy dissipation, and elastic strain decreased with increasing cycle number, with the most substantial reduction occurring between the first and second cycles. A strong inverse correlation was observed between elastic modulus and both energy dissipation and minimum-load strain. The degree of anisotropy ranged from 0.15–0.50 before cycling and narrowed to 0.07–0.27 after ten cycles, indicating that cyclic loading promotes convergence of mechanical properties between the course and wale directions. The Tricot mesh exhibited the lowest anisotropy both before and after cyclic loading, while Sandfly was the most anisotropic. These findings demonstrate that mesh structural architecture and loading direction critically govern mechanical performance and that cyclic loading reduces anisotropy across all designs, with the Tricot configuration offering the most balanced, isotropic-like properties for hernia repair applications.