Elastic modulus for long-term evaluation of the tensile properties of polypropylene meshes in an in vivo rat model

Purpose: Mid-urethral slings have become the gold standard treatment of stress urinary incontinence in women. Their tensile properties should be evaluated in order to measure how they wear off with time. Our objective was a long-term assessment of the tensile properties of 2 synthetic tapes (TVT-O and I-STOP) after in vivo implantation in rats in terms of elastic modulus. Methods: Strips from both meshes were implanted in the abdominal wall of 30 rats, which were sacrificed at 5 time intervals. Their fibers were untangled to single components. Ultimate tensile strength (UTS), strain at UTS and the elastic modulus of each fiber type were measured. Results: I-STOP maintained UTS and strain over time, while TVT-O UTS and strain were significantly reduced. However, the elastic modulus of both tapes remained constant. Conclusions: Both meshes maintained their stiffness and elasticity with time. Elastic modulus could be an appropriate factor to predict long-term implantation outcomes. The clinical significance of such findings remains to be demonstrated by long-term analysis.