title: Levator ani deformation during the second stage of labour.
abstract: A very important medical problem for females is urinary incontinence, sometimes associated with faecal incontinence and pelvic organ prolapse. One of the most common reasons these issues are increasing is clearly the muscle damage during childbirth. This article focusses on understanding the complex behaviour of the levator ani muscles involved in the second stage of labour. A geometrical model obtained from a 23-year-old nulliparous woman was used to simulate childbirth. Several assumptions were introduced in order to simplify the problem without significantly affecting the global response of the system. An anisotropic hyperelastic model was used to characterize the material behaviour; the muscle fibres were assumed to be mostly orientated circumferentially. In addition, particular attention was also put to the boundary conditions of the model. The introduction of the constraints imposed by the coccyx bone in the central area of the levator ani group represents one the most important improvement compared to previous computational models. The maximum deformation and stress were found in the pubococcygeus muscle of the levator ani group. A stretch value close to 2.2 was determined by considering different material parameters. The results seem convincing with respect to medical observation and previous analysis. However, there are still some limitations concerning the material definition and the geometry and trajectory of the head that can be further improved.
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy mario.berardi@ing.unibs.it.
authors.forename: Mario
authors.initials: M
authors.lastname: Berardi
authors.affiliation: Departamento de Ingeniería Mecánica, Tecnológico de Monterrey, Monterrey, México.
authors.forename: Oscar
authors.initials: O
authors.lastname: Martinez-Romero
authors.affiliation: Departamento de Ingeniería Mecánica, Tecnológico de Monterrey, Monterrey, México.
authors.forename: Alex
authors.initials: A
authors.lastname: Elías-Zúñiga
authors.affiliation: Departamento de Ingeniería Mecánica, Tecnológico de Monterrey, Monterrey, México.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Rodríguez
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Ceretti
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Fiorentino
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Donzella
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Avanzini
keywords: Levator ani muscles; anisotropic material; boundary conditions; childbirth; finite element simulation