Australian and New Zealand Journal of Obstetrics and Gynaecology 2006; 46: 368 368 © 2006 The Authors Journal compilation © 2006 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists Blackwell Publishing Asia Letter to the Editor Letters to the Editor Letters to the Editor Re: Biocompatible properties of surgical mesh using an animal model We congratulate the authors 1 on their detailed experimental study in which various meshes were implanted for 12 weeks in rats. In essence, they have shown that multifilamentous tapes had a greater number of macrophages, multinuclear giant cells and fibrous tissue than the monofilamentous tapes. We have, however, several relevant comments on this paper. There is no description of the tissue reaction between the individual filaments of the multifilamentous mesh. Obviously this is important as they comment on the hypothetical disad- vantage of infection occurring in implanted multifilamentous mesh. Our studies in the human at 2 years, and in the rat at 2–8 weeks after implantation, 2 clearly demonstrated that macrophages, multinuclear giant cells and fibroblastic con- nective tissue invade the spaces (often less than 5 micra in width) between filaments. This finding does not accord with the authors’ postulates that macrophages cannot enter spaces that are less than 10 micra in width. Moreover, Gram stains did not reveal the presence of any microorganisms. 2 Interestingly, the authors do not report any obvious sign of infection. 1 Furthermore, when discussing the possibility of infection, they use a reference to sutures, which are an entirely different scenario to implanted mesh. In our animal study, 2 the multifilament tape was ensheathed by a layer of dense connective tissue with fine fibrillar con- nections penetrating into the substance of the mesh. A similar finding was noted during surgery in the human by the second author (PP). This property greatly facilitated removal of the multifilament tape, by incision of the sheath, and simply pulling on the tape. In contrast, the monofilamentous tape was densely adherent to tissue, and was difficult to remove, needing to be excised piece by piece. These properties have potentially serious sequelae if the mesh is in the near vicinity of an organ such as the urethra or rectum. We are in basic agreement with the authors’ statements that many other factors besides the characteristics of the mesh need to be considered when deciding which mesh or tape to use, depending on the biomechanical process that needs to be employed. With regard to their comment on mobility, we draw the readers’ attention to a promising new structural principle for pelvic floor repair which is described elsewhere. 3 Strips of tape are implanted horizontally in the manner of ceiling joists to support the vaginal membrane, which is attached much like a plaster board. This method vastly reduces the amount of tape implanted, and maintains tissue flexibility. J. PAPADIMITRIOU School of Surgery and Pathology UWA P. E. P. PETROS Royal Perth Hospital DOI: 10.1111/j.1479-828X.2006.00609.x References 1 Krause HG, Galloway SJ, Khoo SK, Lourie R, Goh JT. Biocompatible properties of surgical mesh using an animal model. Aust NZ J Obstet Gynaecol 2006; 46: 42–45. 2 Papadimitriou J, Petros PEP. Histological studies of monofila- ment and multifilament polypropylene mesh implants demon- strate equivalent penetration of macrophages between fibrils. Hernia 2005; 9: 75–78. 3 Petros PEP. Reconstructive pelvic floor surgery. In: The Female Pelvic Floor, Function, Dysfunction, and Management According to the Integral Theory. Heidelberg, Germany: Springer, 2004; 77–137.