title: A multi-compartment 3-D finite element model of rectocele and its interaction with cystocele.
abstract: We developed a subject-specific 3-D finite element model to understand the mechanics underlying formation of female pelvic organ prolapse, specifically a rectocele and its interaction with a cystocele. The model was created from MRI 3-D geometry of a healthy 45 year-old multiparous woman. It included anterior and posterior vaginal walls, levator ani muscle, cardinal and uterosacral ligaments, anterior and posterior arcus tendineus fascia pelvis, arcus tendineus levator ani, perineal body, perineal membrane and anal sphincter. Material properties were mostly from the literature. Tissue impairment was modeled as decreased tissue stiffness based on previous clinical studies. Model equations were solved using Abaqus v 6.11. The sensitivity of anterior and posterior vaginal wall geometry was calculated for different combinations tissue impairments under increasing intraabdominal pressure. Prolapse size was reported as pelvic organ prolapse quantification system (POP-Q) point at point Bp for rectocele and point Ba for cystocele. Results show that a rectocele resulted from impairments of the levator ani and posterior compartment support. For 20% levator and 85% posterior support impairments, simulated rectocele size (at POP-Q point: Bp) increased 0.29 mm/cm H2O without apical impairment and 0.36 mm/cm H2O with 60% apical impairment, as intraabdominal pressures increased from 0 to 150 cm H2O. Apical support impairment could result in the development of either a cystocele or rectocele. Simulated repair of posterior compartment support decreased rectocele but increased a preexisting cystocele. We conclude that development of rectocele and cystocele depend on the presence of anterior, posterior, levator and/or or apical support impairments, as well as the interaction of the prolapse with the opposing compartment.
authors.affiliation: Pelvic Floor Research Group, University of Michigan, Ann Arbor, MI, USA; Biomechanics Research Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA. Electronic address: jjluo@umich.edu.
authors.forename: Jiajia
authors.initials: J
authors.lastname: Luo
authors.affiliation: Pelvic Floor Research Group, University of Michigan, Ann Arbor, MI, USA; Biomechanics Research Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Luyun
authors.initials: L
authors.lastname: Chen
authors.affiliation: Pelvic Floor Research Group, University of Michigan, Ann Arbor, MI, USA; Division of Gynecology, Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Dee E
authors.initials: DE
authors.lastname: Fenner
authors.affiliation: Pelvic Floor Research Group, University of Michigan, Ann Arbor, MI, USA; Biomechanics Research Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Ashton-Miller
authors.affiliation: Pelvic Floor Research Group, University of Michigan, Ann Arbor, MI, USA; Division of Gynecology, Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: John O L
authors.initials: JO
authors.lastname: DeLancey
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D052858:Cystocele / Q000503:physiopathology*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008022:Ligaments / Q000503:physiopathology; D008875:Middle Aged; D008954:Models, Biological; D017773:Pelvic Floor / Q000503:physiopathology; D020047:Rectocele / Q000503:physiopathology*
keywords: Biomechanical model; Cystocele; Finite element method; Pelvic floor; Pelvic organ prolapse; Rectocele