Krofta Ladislav, Havelková Linda, Urbánková Iva, Krčmář Michal, Hynčík Luděk, Feyereisl Jaroslav
Institute for the Care of Mother and Child, Podolské nábřeží 157, 147 00, Praha, Czech Republic.
New Technologies-Research Centre, University of West Bohemia, Univerzitní 8, 306 14, Plzeň, Czech Republic.
Int Urogynecol J. 2017 Feb;28(2):275-284. doi: 10.1007/s00192-016-3126-1. Epub 2016 Aug 25.
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.
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.
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.
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.
在阴道分娩过程中，肛提肌（LAM）会发生严重变形。这种压力会导致与拉伸相关的肛提肌损伤。本研究的目的是建立一个复杂的基于MRI的模型，以模拟阴道分娩过程中肛提肌的变化。
建立了女性盆底和胎儿头部的三维有限元模型。模型几何形状基于一名未生育女性和一名1日龄新生儿的MRI数据。材料参数使用文献中的单轴测试数据并通过最小二乘法进行估计。边界条件反映了所有解剖学约束和支撑。然后针对分娩的主要动作进行了阴道分娩模拟。
胎儿头部伸展时，肛提肌髂尾肌部分的平均应力值为4.91 - 7.93兆帕。在胎儿头部伸展开始时，耻骨内脏肌和耻骨直肠肌部分的肛提肌诱导出最高应力值（平均27.46兆帕）。参与应力变化的最后一个肛提肌细分部分是耻骨直肠肌的后内侧部分。胎儿头部伸展结束时，平均应力值为16.89兆帕。肛提肌从其初始静止位置拉长了近2.5倍。
分娩的主要动作显著影响肛提肌随后的不均匀应力分布。应力绝对值在起自耻骨的肌肉部分最高。这些区域发生肌肉损伤并伴有长期并发症的风险最高。
