Expanded polytetrafluoroethylene and polypropylene in the repairing of abdominal wall defects in Wistar rats. Comparative study1 Uso das telas de politetrafluoroetileno e polipropileno no reparo de defeitos da parede abdominal em ratos Wistar. Estudo comparativo

Purpose: To compare the use of polypropylene and PTFE meshes in the treatment of incisional hernias made experimentally on Wistar rats. Methods: The experiment used 24 Wistar rats divided into three cohorts: C-A (ressection of a segment of abdominal wall), E-A (ressection and placement of PTFEe mesh), E-B (resection and placement of polypropylene mesh). After 28 days, the mesh and the surrounding tissue were removed and submitted to macroscopic analysis (assessment of the abdominal wall for presence of abscess in the surgical wound and/or skin necrosis, and adhesions) as well as microscopic analysis (presence of fibrosis, necrosis and abscess, counting of macrophages, mononuclears and polymorphonuclears). Results: Adhesions and abscesses in the surgical wound were observed more commonly associated to the group treated with PTFEe. The size of the fibrous tissue was greater in the group treated with polypropylene. Cohort E-A showed PTFEe mesh enveloped by organized fine connective tissue. No groups presented necrosis on the site of the insertion. The highest mononuclear inflammatory reaction occurred in association to PTFEe when compared to the control group, but the findings for the polypropylene mesh were also significant when compared to the control group. In the analysis of the results obtained for cohorts E-A and E-B, a minimal occurrence of polymorphonuclears was noticed in both groups, which indicates low tissue reactivity to both materials used in the present experiment. Conclusion: Even with epithelization and proliferation of connective tissue, anchorage between PTFEe and abdominal wall is insufficient, which can result in reherniations.