Adhesions on polypropylene versus Sepramesh ® meshes : an experimental study in rats

1 Federal University of Paraná, Department of Surgery, Curitiba, PR, Brazil. Biondo-Simões Adhesions on polypropylene versus Sepramesh® meshes: an experimental study in rats. 2 Rev Col Bras Cir 45(6):e2040 From 1958, the proposal of the use of meshes for correction of hernias by Dr. Francis Usher3 made this treatment model essential, reducing costs and recurrences6,10,12-14. The popularity of the method made the use of meshes the gold-standard treatment in herniorraphies12, allowing the development of prostheses composed of different

Hernias are common debilitating conditions that affect more than one million Americans per year, with more than 350,000 surgeries annually 4 and 400,000 surgeries in Europe 5 , making this the most common procedure in General Surgery 4,6,7 . In Brazil, although we do not have current data, it is estimated that, between 1993 and 1996, 500,000 herniorraphies were performed, with an estimated cost of R$ 100 million 8 . It is believed that over 20 million meshes be deployed per year worldwide 7 .
The development of incisional hernias after abdominal surgeries is frequent 1 , being the most common surgical complication in the United States 3 , with incidence between 2% and 40% 1,5,8,9 and recurrence between 24% and 43% 5 . It is believed that a 1% reduction in the isolated recurrence rate would correspond to a savings of US$ 32 million annually 5 .
The treatment of ventral hernias is essentially surgical 1,10 , with several techniques

Original Article
Adhesions on polypropylene versus Sepramesh® meshes: an experimental study in rats. From 1958, the proposal of the use of meshes for correction of hernias by Dr. Francis Usher 3 made this treatment model essential, reducing costs and recurrences 6,10,[12][13][14] . The popularity of the method made the use of meshes the gold-standard treatment in herniorraphies 12   We randomly divided the sample into two groups, with ten rats each. We inserted both meshes into each animal on the intraperitoneal surface of the abdominal wall, so that each rat was its own control. In Group 1, the polypropylene (PP) mesh was placed on the peritoneal surface to the right of the median incision, and the Sepramesh®, on the left. In Group 2, the meshes' layout was inverted, leaving the polypropylene mesh on the left and the Sepramesh® on the right.
Before the surgical procedure, we kept the rats in quarantine for two weeks for setting in the laboratory. Anesthesia was performed with intramuscular ketamine hydrochloride (50mg/ kg) and xylazine (20mg/kg), supplemented with inhalation induction with isoflurane 1% to 1.5% in a mask associated with 100% oxygen.  For evaluation of the adhesion area, we designed a mold of the same size (10x20mm) on graph paper. For greater accuracy, we resected visceral adhesions for analysis of the portions covered by the meshes. From the projections on the graph paper, we calculated the commitment percentages of each mesh. We considered the meshes fixed to the peritoneum as incorporated, while those supported only by the attachment sutures, as unincorporated.
The results were submitted to statistical analysis by the Mann-Whitney test for means evaluation and the Fisher's test for the frequency, adopting p<0.05 or 5% as a level for rejection of the null hypothesis.

RESULTS
There were no postoperative complications or deaths. We excluded an animal from Group 1 from the statistical analysis because it presented bias in the placement of the mesh. All meshes presented with adhesions. Regarding incorporation, six polypropylene meshes and nine Sepramesh® ones were not incorporated into the parietal peritoneum, being fixed only by the sutures (p=0.2574).
Participated in the adhesions the omentum (67%), the fat of the spermatic cord (40%), the liver (12.5%), the mesentery (7.5%) and loops of small intestine (2.5%) (Figures 4 and 5).     involving a two-dimensional plane and representing a defined site of adhesion after its formation 18 .
In this study, we evaluated adhesions directly by macroscopy and calculation of the affected surface. Sepramesh® and other composite meshes 18,20,23,27 .
In an experimental study in rats, Gaertner et al. 18