Evaluation of three purely polypropylene meshes of different pore sizes in an onlay position in a New Zealand white rabbit model

The aim of the study was to evaluate the influence of the pore size of a polypropylene mesh on the shrinkage and elasticity of the mesh-tissue complex and the inflammatory reaction to the implant in an open onlay hernia repair. Twenty-one 10 x 10 cm samples of polypropylene meshes of a different pore size (3.0 x 2.8 mm-PP3, 1.0 x 0.8 mm-PP1 and 0.6 x 0.5 mm-PP.5) were implanted in an onlay position in 21 New Zealand white rabbits. After 90 days of implantation the shrinkage, elasticity and foreign body reaction (FBR) were assessed. The shrinkage of PP3 was 30.6 +/- A 4.3 %, PP1 49.3 +/- A 2.9 % and PP.5 49.5 +/- A 2.6 %. The shrinkage of PP3 was significantly lower (PP3 x PP1 p = 0.007, PP3 x PP.5 p = 0.005), PP1 and PP.5 were similar. The elasticity was similar. The strength of FBR in mesh pores was similar. The width of foreign body granuloma layers at the mesh-tissue interface was significantly reduced with increasing pore size (inner: PP3 10.1 +/- A 1.2; PP1 12.5 +/- A 2.9; PP.5 17.4 +/- A 5.2 and outer: PP3 21.2 +/- A 2.5; PP1 30.6 +/- A 6.3; PP.5 60.4 +/- A 14.9). All differences between the widths of granuloma layers were statistically significant (p < 0.010). One animal (PP1) was excluded because of a mesh infection. Implantation of polypropylene mesh of a pore size of 3 mm in an onlay position is associated with a significant reduction of shrinkage in comparison to a 1 mm pore lightweight and 0.5 mm pore heavyweight mesh. A pore size increase to 3 mm is not sufficient for an improvement of mesh-tissue complex elasticity in comparison to a 1 mm pore lightweight and 0.5 mm heavyweight mesh. Polypropylene mesh with enlarged pores to 3 mm is associated with a similar strength of FBR in mesh pores and a reduced foreign body granuloma in comparison to a 1 mm pore lightweight and 0.5 mm pore heavyweight mesh.