Tensile strength and host response towards different polypropylene implant materials used for augmentation of fascial repair in a rat model

We compared inflammatory response, fibrosis and biomechanical properties of different polypropylene materials from one manufacturer (Tyco Healthcare) in a rat model for primary fascial repair. Full-thickness abdominal wall defects were primarily repaired using 'overlay' technique. Multifilament implants were Surgipro SPM and SPMW, the latter a wider-weave type of the former. Monofilament SPMM implants and polypropylene suture repair (Surgipro II) served as controls. Explants were evaluated macroscopically and changes in thickness, shrinkage and tensile strength were measured. Inflammatory and connective tissue response was assessed on haematoxylin-eosin and Movat stains. Immunohistochemistry was done to localise rat macrophages/monocytes. Multifilament materials induced a shorter acute inflammatory response and more pronounced chronic inflammatory reaction compared to monofilament implants. Macrophages could be found deep in interstices 7.5 by 12.5 mu m. No difference in collagen deposition and neovascularisation was observed. At 90 days time point, explants reconstructed with tighter woven multifilament SPM were weaker than sutured or SPMM controls. Overall shrinkage of 10% was comparable for all groups.