Transurethral implantation of silicone polymer for stress incontinence: evaluation of a porcine model and mechanism of action in vivo

Objective To evaluate the anatomical location, histological appearances and mechanism of action of silicone polymer (Macroplastique(R)) after transure thral implantation. Materials and methods An in vivo pig model was developed to investigate the organization of Macroplastique 6 weeks after injection. The results were c ompared with the immediate appearance of injected Macroplastique in a surgi cal training device (using isolated pig urethrae) and with the histological appearances of Macroplastique in an explanted human specimen. Results Macroplastique was subserosal in all specimens; it provoked a marke d foreign-body inflammatory reaction, producing firm nodules 6 weeks after implantation. The histological appearances in the in vivo pig model and the human specimen were indistinguishable. Conclusions These findings indicate that the mechanism of action of Macropl astique is to augment pressure transmission to the proximal urethra by prod ucing focal but firm. expansion of periurethral tissues.