Erosion of soft tissue by polypropylene mesh products

Surgical mesh products made from polypropylene (PP) have been extensively used in the treatment of stress urinary incontinence, pelvic organ prolapse and other conditions. Since the onset of the use of such implants, major complications have been reported. Mesh erosion, where neighbouring tissues are worn from the rubbing of mesh, occurs in a significant number of cases. However, there is still a lack in literature exploring the mechanics of this phenomenon. In this study, a purpose-built apparatus was used to generate erosion in soft tissue (porcine muscle) through the application of a force and a reciprocating action. Four different commercial products were tested, all made from knitted PP fibres: Monarc™ Gynecare™ and Obtryx™ slings and Sutulene™ mesh sheet material. A PP suture and three PP sheets with different edge roughness were also tested. Large differences were found in the erosion rates. Significantly, we found that meshes in which the edge had been formed using heat to cause partial melting gave much higher rates of erosion than mechanically cut edges. Heat-formed edges tended to retain their shape whilst mechanically cut edges degraded by unravelling. Several features of the mesh edge appear to be significant, including roughness, flexibility and the tendency to degrade. Constant load (non-reciprocating) tests were also carried out, revealing that creep can also cause erosion. These findings have significance for the design of surgical mesh products to minimise their adverse effects.