Improvement of computer simulated childbirth three-dimensional (3D) model using an individual estimative of levator ani muscle biomechanical behavior

Abstract

Simulations of skeletal muscle biomechanics are based on the principle that parameters of each element describe properties of whole muscle, called the finite-element method. The computer childbirth simulation is a recently developed tool to study the mechanism of pelvic floor injuries during vaginal delivery. Several studies have suggested that childbirth-related injuries may lead to development of urinary incontinence and pelvic organ prolapse. The aim of this study is to compare the stretch ratios of levator ani muscle on simulated childbirths based on MRI data from nuliparous and primiparous women. For these simulations, the dynamic evaluation of levator ani muscle will be performed to evaluate elastic properties of this muscle to modulate the stiffness of levator ani muscle and attachments on the 3D simulations. We anticipate that there will be differences in elastic properties of levator ani muscle. Thirty nulliparous asymptomatic women and thirty asymptomatic primiparous women, age matched, will be evaluated by MRI. The primiparous will be evaluated one and six months after childbearing. Dynamic evaluation will be performed based on MRI images in three different situations, at rest, on Vasalva and in the pelvic muscle contraction. The simultaneous measures of intrabdominal pressure and the changes in volume, longitudinal strain, cross-sectional area and levator hiatus will be used to calculated elastic properties of levator ani muscle. The 3D Slicer software (www.slicer.org) will be used to display pelvic organs in a manner similar to the previous work of the USF group. Specialized finite element modeling and analysis tools will be then applied to the segmented structures to create an appropriate computer model of the bony pelvis, obturator internus, and levator ani muscles for childbirth simulation. Estatistical analysis will use the Mann-Whitney test for comparison between groups. (AU)