The objective of this study was to simulate changes in the LAM during vaginal delivery with respect to the cardinal movements of labor. Our method of obtaining the three-dimensional computer model and the imaging protocol have been published previously. The volunteer/legal representative gave written consent. The neonate was 1 day old, after uncomplicated VD at term, with neurological indications for an MRI brain scan. Female characteristics were 25 years old, BMI 21.9 kg/m 2, nulliparous, Caucasian, no previous vaginal delivery, normal POP-Q points, and absence of PFD symptoms. The geometry of these structures was based on live-subject MRI data. All supporting structures were replaced by boundary conditions. An MRI-based three-dimensional computer model of the bony pelvis, pelvic floor muscles, pelvic floor organs and fetal head was created. The study was approved by the local ethics committee of the authors' institution. The objective of this study was to develop a sophisticated MRI-based finite element model of the female pelvic floor to simulate a child birth for fetal head position in persistent OP and analyze the stress distribution in the LAM with respect to the cardinal movements of labor. To the authors' knowledge, there are no studies describing the material properties of non-cadaveric LAM. Material properties are usually derived from cadaveric LAM uniaxial or biaxial tests. Although these models provide satisfactory insights, they are strongly limited by constitutive data or boundary conditions representing the real anatomy and physiology. Most of them are focused on the second stage of labor, starting from full dilatation of the cervix to the birth of the fetus. Several virtual models of VD have already been developed. This condition is found in up to 5% of deliveries and occurs significantly more often in first labors. Ī persistent occiput posterior (OP) position in the second stage of delivery carries an increased risk of labor complications, obstetric interventions, severe maternal perineal lacerations and anal sphincter injury. This trauma usually causes lifelong complications. These deformations can lead to injuries such as muscle tearing and striated muscle atrophy, owing to pudendal denervation. During VD, the LAM undergoes extremely large deformations to allow the passage of the fetal head. LAM injuries occur in 13–36% of women who have vaginal delivery (VD), and there is conclusive evidence of a connection between these injuries and pelvic floor dysfunction (PFD). In recent years with advances in magnetic resonance imaging (MRI) and four-dimensional sonography, it has also become evident that levator ani muscle (LAM) injuries represent an important part of pelvic floor trauma. In the past decades, the concept of pelvic floor trauma was attributed largely to perineal, vaginal and anal sphincter injuries. Considering the persistent occiput posterior position, the stress increases evenly 3.6 times compared with the optimal head position. The fetal head position during vaginal delivery significantly affects the stress distribution in the levator muscle. For the persistent occiput posterior position, the maximum was detected in the distal posteromedial levator portion at station +6 (mean: 120.28 MPa). For the optimal head position, the maximum stress was found in the anteromedial levator portion at station +8 (mean: 44.53 MPa). The results show the significant increase of the von Mises stress in the levator muscle for the case of a persistent occiput posterior position. The material constants of the hyperelastic Ogden model were measured for the samples of pig levator ani. The von Mises stress distribution was analyzed. Vaginal deliveries considering two positions of the fetal head were simulated: persistent occiput posterior position and uncomplicated occiput anterior position. The uniaxial test was measured using pig samples of the levator to determine the material constants. The model involves the pelvis, fetal head and soft tissues including the levator ani and obturator muscles simulated by the hyperelastic nonlinear Ogden material model. Objective 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.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |