Midurethral slings are used to correct urethral hypermobility in female stress urinary incontinence, defined as the complaint of involuntary urine leakage when the intra-abdominal pressure is increased. Structural and thermal features influence their mechanical properties, which may explain postoperative complications, e.g., erosion, urethral obstruction. We studied the effect of the mesh stiffness on urethral mobility at Valsalva maneuver, under impairment of the supporting structures (levator ani and/or ligaments), by using a numerical model. For that purpose, we modeled a sling with "lower" vs. "higher" stiffness, and evaluated the mobility of the bladder and urethra, that of the urethrovesical junction (the a-angle), and the force exerted at the fixation of the sling. The effect of impaired levator ani or pubourethral ligaments alone on the organs displacement and a-angle opening was similar, showing their important role together on urethral stabilization. When the levator ani and all the ligaments were simulated as impaired, the descent of the bladder and urethra went up to 25.02mm, that of the bladder neck was 14.57mm, and the a-angle was 129.7°, in the range of what was found in women with SUI. Both meshes allowed returning to normal positioning, although at the cost of higher force exerted by the mesh with "higher" stiffness (3.4N against 2.3N), which can relate to tissue erosion. This finite element analysis allowed mimicking the biomechanical response of the pelvic structures in response to changing a material property of the midurethral synthetic mesh.
Journal of biomechanical engineering. 2017 May 02 [Epub ahead of print]
Sofia Brandão, Marco Parente, Thuane Huyer Da Roza, Elisabete Silva, Isabel Maria Ramos, Teresa Mascarenhas, Renato Manuel Natal Jorge
Dep. of Radiology, Centro Hospitalar e São João - EPE (CHSJ-EPE) / Faculty of Medicine, University of Porto, Portugal Alameda Professor Hernâni Monteiro, 4200 - 319 Porto, PortugalAssociated Laboratory for Energy, Transports and Aeronautics (LAETA), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI); Faculty of Engineering, University of Porto, Portugal Rua Dr. Roberto Frias s/n; 4200 - 465 Porto, ., Associated Laboratory for Energy, Transports and Aeronautics (LAETA), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI); Faculty of Engineering, University of Porto, Portugal Rua Dr. Roberto Frias s/n; 4200 - 465 Porto, ., Biomechanics Laboratory, Center of Health and Sport Sciences, Santa Catarina State University (CEFID/UDESC), Florianópolis, Brazil Rua Paschoal Simone, 358, Bairro dos Coqueiros, Florianópolis, Santa Catarina, BrazilAssociated Laboratory for Energy, Transports and Aeronautics (LAETA), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI); Faculty of Engineering, University of Porto, Portugal Rua Dr. Roberto Frias s/n; 4200 - 465 Porto, ., Associated Laboratory for Energy, Transports and Aeronautics (LAETA), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI); Faculty of Engineering, University of Porto, Portugal Rua Dr. Roberto Frias s/n; 4200 - 465 Porto, ., Dep. of Radiology, CHSJ-EPE / Faculty of Medicine, University of Porto, Portugal Alameda Professor Hernâni Monteiro, 4200 - 319 Porto, ., Dep. of Obstetrics and Gynecology, CHSJ-EPE / Faculty of Medicine, University of Porto, Portugal Alameda Professor Hernâni Monteiro, 4200 - 319 Porto, ., Associated Laboratory for Energy, Transports and Aeronautics (LAETA), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI); Faculty of Engineering, University of Porto, Portugal Rua Dr. Roberto Frias s/n; 4200 - 465 Porto, .