Retraction and fibroplasia in a polypropylene prosthesis: experimental study in rats

The treatment of hernia, independent of anatomical site and technique utilized, generally involves using prostheses, which may cause complications, despite their unarguable advantage in allowing safe reinforcement. An example of this is possible retraction, which causes discomfort and hernia recurrence. Polypropylene is still the most often used biomaterial of the great number available. The purpose of this study is to evaluate the amount of retraction of the polypropylene mesh, as well as the histological reactions that accompany this phenomenon.

Polypropylene meshes (Marlex) were inserted in an anterior position to the whole abdominal aponeurosis of 25 Wistar rats (Rattus norvegicus albinus). The animals were divided into groups and another intervention was performed 7, 28, and 90 days later to measure the dimensions of the prostheses and to calculate the final area. Histological analysis was performed with hematoxylin-eosin to evaluate neutrophils, macrophages, giant cells, and lymphocytes surrounding the mesh threads in ten random fields of each slide.

Seven days after the mesh was inserted, the mean rate of retraction was 1.75% (P = 0.64); at 28 days, it was 3.75% (P = 0.02); and at 90 days, it was 2.5% (P = 0.01). As to the histological analysis, there was a total decline of neutrophils and a progressive increase of macrophages, giant cells, and lymphocytes proportional to the post-implant time of the mesh (P < 0.05).

There was a statistically significant retraction of 3.75% at 28 days and 2.5% at 90 days after the prosthesis was inserted. There is a well-established sequence of cellular events which aim at synthesizing new connective tissue to reinforce the mesh.