Implants in the abdominal wall of the rat

An experimental model is presented that allows qualitative as well as quantitative studies of the soft tissue response to implant materials used in reconstructive surgery. Plugs of non-alloyed titanium and polymers (Teflon, Delrin) were inserted into the abdominal wall of rats, with a portion of the plug penetrating through the peritoneum into the abdominal cavity. The tissue reaction was evaluated by means of light and electron microscopy for up to 9 weeks after insertion. Titanium implants were in direct contact with the connective tissue without intervening inflammatory cells. The defect in the peritoneum was sealed by a close apposition of the mesothelial membrane to the titanium surface and no connective tissue surrounded the intra-peritoneal portion of the plug. In contrast, a fibrous capsule surrounded the intra-peritoneal portion of Teflon and Delrin implants. A reactive zone consisting of active macrophages and giant cells was present at the surface of these implants separating the implant from the surrounding fibrous capsule. This study shows that the tissue response at the interface to foreign materials can be studied using light and electron microscopic techniques and that profound differences in tissue response exist between different materials.