Comparison of a new type of polytetrafluoroethylene patch (Mycro Mesh) and polypropylene prosthesis (Marlex) for repair of abdominal wall defects.

Background: Two types of prosthetic material used for repairing hernial defects of the abdominal wall were compared: Mycro Mesh and Marlex. Mycro Mesh (MM) is a new polytetrafluoroethylene product of layered, microporous structure. Macroscopically, it presents regularly distributed, 2-mm orifices that perforate the biomaterial. Marlex (PL) is a well-known polypropylene mesh product with a macroporous structure.

Study Design: In 24 white New Zealand rabbits, a full-thickness (except skin) 5 x 7-cm defect was created in the anterior wall of the abdomen. Defects were repaired with either MM (n = 12) or PL (n = 12) implants and studied at 14, 30, 60, and 90 days after implantation. Samples of the interfaces between prosthesis and subcutaneous tissue, visceral peritoneum, and receptor tissue, respectively, were studied. Samples were processed for optical microscopy and scanning electron microscopy (SEM). An immunohistochemical study was made using RAM-11, a monoclonal antibody specific for rabbit macrophages. The tensile strength of the repairs was made using an Instron tensiometer on 2-cm wide transversal strips that included the prosthesis and its anchor zones to the receptor tissue.

Results: The formation of adhesions between the prosthesis and intestine was important with the PL implants but not with the MM implants. Optical microscopy and SEM showed formation of an organized connective tissue surrounding the MM implants. At 90 days, compact bridges of connective tissue linked the tissue on the subcutaneous and peritoneal sides of the prosthesis. The PL implants became integrated into a disorganized, highly vascularized connective tissue. The intensity of the macrophage response was similar in both prostheses and decreased between days 14 and 90 (Student-Newman-Keuls test p = 0.01). The tensile strength of the PL implants was greater than that of the MM implants. At 90 days, the tensile strength of the PL implants was mean equals 33.11 N and of the MM implants, mean equals 22.65 N (Mann-Whitney test p < 0.001).

Conclusions: The tissue integration of the PL and MM implants differed; fewer visceral adhesions formed on MM than on PL; the macrophage reaction was not determinant of the success of failure of either biomaterial; and the tensile strength of the prosthesis-receptor tissue interface was much greater in the PL implants than in the MM implants.