Developing a new methodology to characterize in vivo the passive mechanical behavior of abdominal wall on an animal model

Abstract

The most common surgical repair of abdominal wall hernia goes through implanting a mesh that substitutes the abdominal muscle/fascia while it is healing. To reduce the risk of relapse or possible complications, this mesh needs to mimic the mechanical behavior of the muscle/fascia, which nowadays is not fully determined. The aim of this work is to develop a methodology to characterize in vivo the passive mechanical behavior of the abdominal wall. For that, New Zealand rabbits were subjected to pneumoperitoneum tests, taking the inner pressure from 0 mmHg to 12 mmHg, values similar to those used in human laparoscopies. Animals treated were divided into two groups: healthy and herniated animals with a surgical mesh (polypropylene Surgipro(TM) Covidien) previously implanted. All experiments were recorded by a stereo rig composed of two synchronized cameras. During the postprocessing of the images, several points over the abdominal surface were tracked and their coordinates extracted for different levels of internal pressure. Starting from that, a three dimensional model of the abdominal wall was reconstructed. Pressure-displacement curves, radii of curvature and strain fields were also analysed. During the experiments, animals tissue mostly deformed during the first levels of pressure, showing the noticeable hyperelastic passive behavior of abdominal muscles. Comparison between healthy and herniated specimen displayed a strong stiffening for herniated animals in the zone where the high density mesh was situated. Cameras were able to discern this change, so this method can be used to measure the possible effect of other meshes.

Meta-analysis of closure of the fascial defect during laparoscopic incisional and ventral hernia repair

“…Defects in the abdominal wall alter the compliance experienced locally by tissues. CFD is likely to reduce local stress on scarred tissue that already has reduced tensile strength.…”

Physical structure and mechanical properties of knitted hernia mesh materials: A review

“…Currently, the use of knitted mesh for hernia repair is a common implantation method [10–13]. Each year 20 million meshes are being implanted to repair hernia in the world [7,14–17] and synthetic meshes are involved in 80% of hernia surgeries [18]. The most common textile implants are polypropylene, polyester, polytetrafluoroethylene (PTFE) and expanded polytetrafluoroethylene (ePTFE).…”

Mechanical behavior of surgical meshes for abdominal wall repair: In vivo versus biaxial characterization

“…Further information from other mechanical tests, such as inflation or bulge test, would be useful to complete the characterization. The in vivo study limitations were already mentioned in Simón-Allué et al (2015). Moreover, widen the in vivo experimentation to the use of the other meshes involved in the study, as the SS, would help to complete the results.…”