Effect of repetitive loading on the mechanical properties of synthetic hernia repair materials

Background: Hernia repair materials undergo repeated loading while in the body, and the impact on mechanical properties is unknown. It was hypothesized that exposure to repetitive loading would lead to decreased tensile strength and increased strain, and that these differences would become more pronounced with greater loading and unloading sequences. Study Design: Polypropylene, expanded polytetrafluoroethylene, composite barrier, and partially absorbable meshes were evaluated. Twenty specimens (7.5 × 7.5 cm) were prepared from each material. Five specimens were subjected to ball burst testing to determine baseline biomechanical properties. Cycles of 10, 100, and 1,000 loading sequences were also performed (n = 5 each). Results: BardMesh (CR Bard/Davol), Dualmesh (WL Gore), and Prolene (Ethicon) exhibited significantly reduced tensile strength; BardMesh, Proceed (Ethicon), Prolene, ProLite (Atrium Medical), ProLite Ultra (Atrium Medical), and Ultrapro (Ethicon) exhibited significantly increased strain after exposure to 1,000 cycles compared with their baseline properties. BardMesh and Prolene demonstrated both reduced tensile strength and increased strain values after 1,000 cycles, suggesting that repetitive loading has the greatest effects on these materials. In addition, BardMesh and Prolene exhibited progressively worsening effects as the number of cycles was increased. Conclusions: Deterioration of the tensile strength of the mesh or an increase in the ability of the mesh material to stretch (ie, increased strain values) could potentially lead to hernia recurrence or a poor functional result. However, the results of this study should not be interpreted to mean that hernia repair materials will fail in the body after only 10, 100, or 1,000 cycles. The conditions used in this study were more extreme than most physiologic scenarios and were intended as a pilot investigation into how the mechanical properties of hernia repair materials are affected by in vitro cyclic testing.