Polypropylene in the intra-abdominal position: Influence of pore size and surface area

Background. Polypropylene is a material widely used in surgery. Because of its association with formation of enterocutaneous fistulae and adhesions, direct contact between mesh and intestine is avoided. The following study was designed to investigate the adhesive potential of different polypropylene meshes when placed in direct contact with intestine. Material and methods. In an established experimental model, a total of 45 chinchilla rabbits underwent laparoscopic placement of meshes with different pore size (Group I: monofilament PP 0.6 mm, Group II: monofilament PP 2.5 mm, Group III: multifilament PP 4.0 mm) with the Intra-Peritoneal-Onlay-Mesh Technique (IPOM). The degree of adhesion formation was measured after 7, 21, and 90 days, evaluated by an adhesion score, quantified by computer-assisted planimetry, followed by histological and morphometric investigation of the perifilamental granuloma formation. Results. The heavyweight, small porous polypropylene meshes (PP 0.6) showed significantly stronger adhesion formation at all intervals of investigation compared with the lightweight meshes with a pore size >2.5 mm. Between the two different lightweight mesh variations, there was no significant difference. Granuloma formation was lowest in large-pore-size monofilament meshes (PP 2.5). Conclusion. The IPOM rabbit model is suitable for investigation of biomaterials in the intra-abdominal position. Our results show that the adhesive potential is significantly influenced by the pore size. However, the extent of the foreign-body reaction seems also to be influenced by the filament structure, respectively, the surface area, favouring monofilament material.