INTRODUCTION AND HYPOTHESIS: 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. METHODS: 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. 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. RESULTS: The 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). CONCLUSIONS: The 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.

• Klíčová slova
• FEM modeling, Levator ani muscle trauma, Ogden material model, Persistent occiput posterior position, Vaginal delivery,
• MeSH
• analýza metodou konečných prvků MeSH
• naléhání plodu * MeSH
• pánevní dno diagnostické zobrazování   MeSH
• plod * MeSH
• prasata MeSH
• těhotenství MeSH
• vedení porodu MeSH
• zvířata MeSH
• Check Tag
• těhotenství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

INTRODUCTION AND HYPOTHESIS: During vaginal delivery, the levator ani muscle (LAM) undergoes severe deformation. This stress can lead to stretch-related LAM injuries. The objective of this study was to develop a sophisticated MRI-based model to simulate changes in the LAM during vaginal delivery. METHODS: A 3D finite element model of the female pelvic floor and fetal head was developed. The model geometry was based on MRI data from a nulliparous woman and 1-day-old neonate. Material parameters were estimated using uniaxial test data from the literature and by least-square minimization method. The boundary conditions reflected all anatomical constraints and supports. A simulation of vaginal delivery with regard to the cardinal movements of labor was then performed. RESULTS: The mean stress values in the iliococcygeus portion of the LAM during fetal head extension were 4.91-7.93 MPa. The highest stress values were induced in the pubovisceral and puborectal LAM portions (mean 27.46 MPa) at the outset of fetal head extension. The last LAM subdivision engaged in the changes in stress was the posteromedial section of the puborectal muscle. The mean stress values were 16.89 MPa at the end of fetal head extension. The LAM was elongated by nearly 2.5 times from its initial resting position. CONCLUSIONS: The cardinal movements of labor significantly affect the subsequent heterogeneous stress distribution in the LAM. The absolute stress values were highest in portions of the muscle that arise from the pubic bone. These areas are at the highest risk for muscle injuries with long-term complications.

• Klíčová slova
• Levator ani muscle, MRI modeling, Vaginal delivery,
• MeSH
• analýza metodou konečných prvků * MeSH
• anatomické modely * MeSH
• biomechanika MeSH
• distorze a distenze etiologie   MeSH
• dospělí MeSH
• hlava anatomie a histologie   MeSH
• kosterní svaly zranění   MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• novorozenec MeSH
• pánevní dno anatomie a histologie   diagnostické zobrazování   fyziologie   MeSH
• plod anatomie a histologie   MeSH
• pružnost MeSH
• těhotenství MeSH
• vedení porodu škodlivé účinky   MeSH
• zobrazování trojrozměrné metody   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• novorozenec MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

INTRODUCTION AND HYPOTHESIS: This study seeks to assess the effects of forceps-assisted delivery on the levator hiatus. METHODS: Seventy-six women were investigated 12 months after forceps-assisted delivery. Introital three-/four-dimensional ultrasound measured volumes at rest and during the Valsalva maneuver. Morphological parameters analyzed were angle gamma, hiatal area, pubovisceral angle, and continuity between the muscle and pelvic sidewall. Avulsion was diagnosed by loss of continuity. RESULTS: Forty-eight women had avulsion injuries, 23 had bilateral, and 25 had unilateral. Bilateral avulsion increased hiatal area during straining and at rest and was associated with changes in bladder neck position at rest. Unilateral avulsion injury was associated with a higher pubovisceral angle on the side of the avulsion. CONCLUSION: Forceps-assisted vaginal delivery is associated with levator ani injury. Avulsion of the pubovisceral muscle seems more common after forceps delivery than after spontaneous vaginal delivery. Avulsion alters hiatal shape and area and influences the position and mobility of the anterior compartment.

• MeSH
• dospělí MeSH
• extrakce porodnická škodlivé účinky   MeSH
• lidé MeSH
• pánevní dno diagnostické zobrazování   zranění   MeSH
• pilotní projekty MeSH
• ultrasonografie MeSH
• zobrazování trojrozměrné MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH