A Geometric Capacity-Demand Analysis of Maternal Levator Muscle Stretch Required for Vaginal Delivery
A Geometric Capacity-Demand Analysis of Maternal Levator Muscle Stretch Required for Vaginal Delivery
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DOI：
10.1115/1.4032424
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发表时间：
2016-02-01
影响因子：
1.7
通讯作者：
Ashton-Miller, James A.
中科院分区：
文献类型：
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作者：
Tracy, Paige V.;DeLancey, John O.;Ashton-Miller, James A.
由于肛提肌（LA）损伤发生在大约13%的阴道分娩中，因此需要更好地预防它们。在本文的第一部分中，我们分析了骨骼和软组织因素，这些因素有助于产妇骨盆和盆底的几何“能力”，以分娩胎头，而不会导致产妇软组织的牵拉损伤。在第二部分中，我们量化了需求的范围，以胎儿头部大小和形状的变化为代表，放置在母亲的骨盆底。在第三部分中，我们分析了容量与需求的几何比g，以确定母亲是否可以在没有牵拉损伤的情况下生产给定尺寸的头部。第一部分敏感性分析的结果表明，初始软组织环长度（SL）对产妇的能力有最大的影响，其次是软组织环的长度以上的耻骨下支在最终冠，然后耻骨下弓角（SPAA）和头部大小，最后提肌起点分离距离。我们发现，耻骨直肠部的提上睑肌更接近尾部的起源有助于保护它免受耻骨内脏部常见的牵拉损伤。第二部分胎头成型指数（MI）和胎头大小显示胎儿头围值范围为253至351 mm，在面部出现时将增加至11 mm。第三部分对g的容量需求分析表明，仅根据几何形状，第10百分位数的母体容量预测所有头部尺寸的损伤，第25百分位数的母体容量可以提供所有头部尺寸的一半，而第50百分位数的母体容量可以提供任何尺寸的头部而不受伤。如果超声成像可以操作，使比值g的测量，它可能会被用来有用地告知妇女在阴道分娩期间的提肛损伤的风险水平。
Because levator ani (LA) muscle injuries occur in approximately 13% of all vaginal births, insights are needed to better prevent them. In Part I of this paper, we conducted an analysis of the bony and soft tissue factors contributing to the geometric "capacity" of the maternal pelvis and pelvic floor to deliver a fetal head without incurring stretch injury of the maternal soft tissue. In Part II, we quantified the range in demand, represented by the variation in fetal head size and shape, placed on the maternal pelvic floor. In Part III, we analyzed the capacity-to-demand geometric ratio, g, in order to determine whether a mother can deliver a head of given size without stretch injury. The results of a Part I sensitivity analysis showed that initial soft tissue loop length (SL) had the greatest effect on maternal capacity, followed by the length of the soft tissue loop above the inferior pubic rami at ultimate crowning, then subpubic arch angle (SPAA) and head size, and finally the levator origin separation distance. We found the more caudal origin of the puborectal portion of the levator muscle helps to protect it from the stretch injuries commonly observed in the pubovisceral portion. Part II fetal head molding index (MI) and fetal head size revealed fetal head circumference values ranging from 253 to 351 mm, which would increase up to 11mm upon face presentation. The Part III capacity-demand analysis of g revealed that, based on geometry alone, the 10th percentile maternal capacity predicted injury for all head sizes, the 25th percentile maternal capacity could deliver half of all head sizes, while the 50th percentile maternal capacity could deliver a head of any size without injury. If ultrasound imaging could be operationalized to make measurements of ratio g, it might be used to usefully inform women on their level of risk for levator injury during vaginal birth.