A NEW-TYPE OF POLYTETRAFLUOROETHYLENE PROSTHESIS (MYCRO-MESH) - AN EXPERIMENTAL-STUDY

Comparisons were made of the tissue response to the implantation of tw o different polytetrafluoroethylene prostheses: Soft Tissue Patch (STP ) and Mycro Mesh (MM). A 7 x 5 cm prosthesis of STP (n = 12) or MM (n = 12) was implanted into a defect of the same size (involving all laye rs except skin) created in the anterior abdominal wall in 24 New Zeala nd rabbits. The prostheses were anchored to the recipient tissue, in d irect contact with the intestinal loops and connective tissue. After 1 4, 30, 60 and 90 days, groups of six implants were studied macroscopic ally and samples were taken to be processed by light microscopy, scann ing electron microscopy (SEM), immunohistochemical studies and tensiom etry. All animals were valid for the study. In th ree cases STP implan ts presented very loose adhesions in the peripheral zones correspondin g to the sutures. They were also observed on three MM implants, in the area of the perforations. Light and scanning microscopy revealed the formation of a capsule of scar tissue surrounding both types of prosth esis. At day 90, bridges of connective tissue had formed in the perfor ated areas of MM. Good vascularization was established in the areas of recipient tissue corresponding to both implants. The macrophage react ion to both biomaterials was maximal at 14 days, after which it progre ssively decreased until day 90. Tensile testing revealed no significan t differences between the two biomaterials. It is concluded that (a) b ehaviour in the peritoneal interface is similar in the two prostheses, (b) both biomaterials become encapsulated rather than integrated into the recipient tissue, (c) the foreign body reaction does not determin e the success or failure of the implants, (d) The perforations of the MM prosthesis do not increase its resistance to stress, or at least no t after 90 days of implantation into rabbit abdominal wall.