Abstract
Introduction and hypothesisObjective of this study was to develop an MRI-based finite element model and simulate a childbirth considering the fetal head position in a persistent occiput posterior position.MethodsThe model involves the pelvis, fetal head and soft tissues including the levator ani and obturator muscles simulated by the hyperelastic nonlinear Ogden material model. The uniaxial test was measured using pig samples of the levator to determine the material constants. Vaginal deliveries considering two positions of the fetal head were simulated: persistent occiput posterior position and uncomplicated occiput anterior position. The von Mises stress distribution was analyzed.ResultsThe material constants of the hyperelastic Ogden model were measured for the samples of pig levator ani. The mean values of Ogden parameters were calculated as: μ1 = 8.2 ± 8.9 GPa; μ2 = 21.6 ± 17.3 GPa; α1 = 0.1803 ± 0.1299; α2 = 15.112 ± 3.1704. The results show the significant increase of the von Mises stress in the levator muscle for the case of a persistent occiput posterior position. For the optimal head position, the maximum stress was found in the anteromedial levator portion at station +8 (mean: 44.53 MPa). For the persistent occiput posterior position, the maximum was detected in the distal posteromedial levator portion at station +6 (mean: 120.28 MPa).ConclusionsThe fetal head position during vaginal delivery significantly affects the stress distribution in the levator muscle. Considering the persistent occiput posterior position, the stress increases evenly 3.6 times compared with the optimal head position.
Highlights
Introduction and hypothesisObjective of this study was to develop an magnetic resonance imaging (MRI)-based finite element model and simulate a childbirth considering the fetal head position in a persistent occiput posterior position
The table contains the von Mises stress distribution in the levator ani muscle (LAM) during vaginal delivery with respect to the cardinal movements of labor where the fetal head is in the occiput anterior (OA) position
The fetal head initially distends the iliococcygeal muscle (ICm) portion of the LAM at station −1 and 0, respecting the occiput posterior (OP) and OA fetal head position
Summary
Introduction and hypothesisObjective of this study was to develop an MRI-based finite element model and simulate a childbirth considering the fetal head position in a persistent occiput posterior position. In recent years with advances in magnetic resonance imaging (MRI) and four-dimensional sonography, it has become evident that levator ani muscle (LAM) injuries represent an important part of pelvic floor trauma [1, 2]. During VD, the LAM undergoes extremely large deformations to allow the passage of the fetal head [5]. These deformations can lead to injuries such as muscle tearing and striated muscle atrophy, owing to pudendal denervation [6]. This trauma usually causes lifelong complications [7]
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