Satisfactory biomechanical compatibility of implants is important for obtaining desired tissue repair efficiency. Here, we investigated the combined effects of three important influencing factors, mesh orientation, defect location and size, on biomechanical compatibility of a typical anisotropic mesh by both computational simulation and animal experiment.

Numerical models of rabbits were developed based on CT images and material constitutive models obtained by uniaxial tests, during which two orientations, two defect locations and two defect sizes were investigated. Corresponding pneumoperitoneum tests on rabbits and non-invasive measurements on the displacement of abdominal wall surface were performed for validation.

Numerical results showed that the displacement of abdominal wall was limited when the stiffest direction of mesh was parallel to the cranio-caudal direction, but the stress in suture area was greatly reduced. When the defect was located at the junction of different muscles, the strain distribution became uneven. In addition, for the defects with smaller size, difference between the results caused by different mesh orientations was smaller. Animal experimental results were in good agreement with the numerical results. Further simulations for a hypothetical mesh orientation showed that the meshes exhibited better biomechanical compatibility when their stiffest direction was consistent with that of oblique muscles for all four different defects.

The mesh orientation was the most influential factor and the proper orientation of the mesh was not necessarily consistent with the anisotropy of the defect tissue. In addition, the mesh design with asymmetric stiffness should be considered for defects at the junction of different tissues. Finally, it is possible to align the stiffest direction of the mesh with that of the defect tissue in repairing small defects to achieve better compliance. Our findings could provide some reliable and instructive guidelines for high-performance anisotropic meshes development and their appropriate selection and placement in surgery. And methods proposed in this study could be used to comprehensively and instructively evaluate the biomechanical compatibility of hernia meshes, predict their repair effect, and determine their appropriate positioning before they are put into clinical use.