BIOMECHANICS OF SIMULATED VAGINAL BIRTH

出生相关损伤的生物力学研究 本研究的总体目标是更好地了解产妇阴道分娩的相关机制。 第二产程结束时的损伤。影响油井阻力的主要因素 盆底肌肉伸展，因为它们抵抗胎头向下下降，是它们的粘滞松解剂 材料特性。足月妊娠对这些特性的影响从未被记录在案， 部分原因是在分娩期间很难获得未受损的人类盆底组织样本。 因此，在目标1中，我们将使用等双轴测试和逐步应力松弛分析来 描述足月妊娠对骨的本构规律和力学行为的影响 大鼠和松鼠猴的哺乳类盆底组织。还将进行单轴破坏试验 以确定妊娠和测试方向对这些组织中极限拉应力的影响。 在AIM 2.1中，我们将开发一个特定于对象的三维有限元生物力学模型 从工位+2开始的产程，显示胎头、盆底五大肌肉 以及相关软组织，以及随时间变化的母体驱逐力。在AIM 2.2中，我们将 通过将模型预测与孕妇体内实验结果进行比较来验证模型预测 女人。这些包括在横断面处测量的后方加权窥镜的时间位移， 胎头戴冠后阴道直径增大的时间进程。 在AIM 2.3中，我们将研究(A)胎头朝向，(B)头盆不称，(C) 母体耻骨下弓角，(D)硬膜外，(E)产钳使用，(F)会阴切开术， 盆底肌肉组织最大应力的方向和位置。压力与压力之比 极限拉应力被视为组织损伤风险的量度。这些观察结果将会产生 对与最大伤害风险相关的因素的洞察，并应导致更好的方法 防止这些伤害。

Biomechanics of Birth-Related Injuries The overall goal of this research is to better understand the mechanisms of maternal vaginal birthrelated injury at the end of the second stage of labor. The main factor affecting the resistance of the pelvic floor muscles to stretch as they resist the downward descent of the fetal head is their viscoleastic material properties. The effect of term pregnancy on these properties has never been documented, partly due to the difficulty of obtaining sample of undamaged human pelvic floor tissues during birth. In AIM 1, therefore, we will use equi-biaxial testing and stepwise stress relaxation assays to characterize the effect of term pregnancy on the constitutive law and mechanical behavior of mammalian pelvic floor tissues in rat and squirrel monkey. Uniaxial failure tests will also be conducted to determine the effect of pregnancy and test direction on the ultimate tensile stress in these tissues. In AIM 2.1 we will develop a subject-specific, 3-D finite element biomechanical model of the second stage of labor from Station +2 on with representations of the fetal head, five major pelvic floor muscles and related soft tissues, as well as the time-varying maternal expulsive force. In AIM 2.2 we will validate the model predictions by comparing them against the results of in vivo experiments in pregnant women. These involve the measured temporal displacement of a posterior weighted speculum at Csection, and the time course of the increase in vaginal diameter upon fetal head crowning. In AIM 2.3 we will investigate the effect of (a) fetal head orientation, (b) cephalopelvic disproportion, (c) maternal sub-pubic arch angle, (d) epidural, (e) forceps use, and (f) episiotomy on the magnitude, direction and location of maximum pelvic floor muscle tissue stress. The ratio of that stress to the ultimate tensile stress is taken as a measure of the risk of tissue injury. These observations will yield insights into the factors associated with the greatest risk for injury, and should lead to better methods of preventing these injuries.