[Biomechanical effects of the inclusion of holes to facilitate the integration in monofilament polypropylene meshes: an experimental study].

OBJECTIVE To evaluate the biomechanical properties of a type of monofilament polypropylene mesh used to repair vaginal prolapse, as well as the effects of the inclusion of standard size orifices, called "helper orifices," on the interface resistance in the receiving area. MATERIAL AND METHODS Forty female Wistar rats, 3 month-old, received an implant of monofilament polypropylene mesh, measuring 24 x 11 mm with no orifices, on left side of the abdominal wall (block 1). On the right side, a similar mesh with two circular orifices (6 mm diameter) was implanted (block 2). The rats were euthanized 90 days later and their abdominal walls were removed and divided into two blocks. The biomechanical study used a precision tensiometer in which the mesh was uniaxially tensioned until it was loosened from the tissue interface. In order to determine the tissue adherence and elasticity in each group, the following variables were analyzed: maximum load; deflection at maximum load; work to maximum load; stiffness as well as load, deflection and work at detachment the mesh. RESULTS With the exception of stiffness, all the other variables showed statistical differences between the groups, considering that they were increased in meshes with orifices (p<0.001). The inclusion of standard size orifices reduced 30% of the mesh weigth. CONCLUSION Besides reducing the weight and amount of material, the inclusion of standard size orifices in the monofilament macroporous polypropylene mesh improved the elasticity and adherence to the tissues when implanted in the interface of the abdominal wall in adult female rats.