title: Establishing the biomechanical properties of the pelvic soft tissues through an inverse finite element analysis using magnetic resonance imaging.
abstract: The mechanical characteristics of the female pelvic floor are relevant when explaining pelvic dysfunction. The decreased elasticity of the tissue often causes inability to maintain urethral position, also leading to vaginal and rectal descend when coughing or defecating as a response to an increase in the internal abdominal pressure. These conditions can be associated with changes in the mechanical properties of the supportive structures-namely, the pelvic floor muscles-including impairment. In this work, we used an inverse finite element analysis to calculate the material constants for the passive mechanical behavior of the pelvic floor muscles. The numerical model of the pelvic floor muscles and bones was built from magnetic resonance axial images acquired at rest. Muscle deformation, simulating the Valsalva maneuver with a pressure of 4 KPa, was compared with the muscle displacement obtained through additional dynamic magnetic resonance imaging. The difference in displacement was of 0.15 mm in the antero-posterior direction and 3.69 mm in the supero-inferior direction, equating to a percentage error of 7.0% and 16.9%, respectively. We obtained the shortest difference in the displacements using an iterative process that reached the material constants for the Mooney-Rivlin constitutive model (c10=11.8 KPa and c20=5.53 E-02 KPa). For each iteration, the orthogonal distance between each node from the group of nodes which defined the puborectal muscle in the numerical model versus dynamic magnetic resonance imaging was computed. With the methodology used in this work, it was possible to obtain in vivo biomechanical properties of the pelvic floor muscles for a specific subject using input information acquired non-invasively.
authors: LAETA-INEGI, Faculty of Engineering, University of Porto, Porto, Portugal silva.elisabete3@gmail.com.
authors: M E T
authors: ME
authors: Silva
authors: LAETA-INEGI, Faculty of Engineering, University of Porto, Porto, Portugal Department of Radiology, Centro Hospitalar de São João-EPE, Faculty of Medicine, University of Porto, Porto, Portugal.
authors: S
authors: S
authors: Brandão
authors: LAETA-INEGI, Faculty of Engineering, University of Porto, Porto, Portugal.
authors: M P L
authors: MP
authors: Parente
authors: Department of Gynecology and Obstetrics, Centro Hospitalar de São João-EPE, Faculty of Medicine, University of Porto, Porto, Portugal.
authors: T
authors: T
authors: Mascarenhas
authors: LAETA-INEGI, Faculty of Engineering, University of Porto, Porto, Portugal.
authors: R M
authors: RM
authors: Natal Jorge
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017773:Pelvic Floor / Q000000981:diagnostic imaging* / Q000502:physiology*
keywords: Soft tissues; inverse finite element analysis; material constants; pelvic floor muscles