Biomechanics of Birth-Related Injuries

大约15%的女性在阴道分娩时会遭受骨盆肌肉损伤，这可以通过磁共振成像（MR）证实。我们的几何模型表明，在出生的第二阶段，骨盆底肌肉拉伸到原来长度的3.3倍。基于MR成像、组织学、研究和生物力学模型，当损伤发生时，我们假设在一些女性中，最初的耻骨内脏肌附着点断裂（1型损伤），随后是肛提腱弓耻骨附着点撕脱（2型损伤）。我们寻求资金， 这些损伤区域的组织变化，并记录其失效载荷。 目的1将表征30具尸体的耻骨内脏和腱弓组织的形态学和组织学、双轴材料特性（如适用）和单轴失效特性。在20名志愿者中，我们将使用超声弹性成像来表征妊娠对会阴体弹性的影响。 AIM 2将使用Aim 1数据来完善从Station +2开始的第二产程的受试者特定的三维有限元粘超弹性生物力学模型。我们将根据1型/2型损伤的顺序来检验上述假设，并进行参数研究以确定增加或减少1型和2型损伤风险的生物力学因素。我们将验证模型与立体摄影测量会阴下降10名劳动妇女。 由于产妇疲惫是器械分娩和提上睑肌损伤的主要风险，在AIM 3中，我们将使用重复测量设计来量化40名21至30岁的健康非妊娠志愿者的结局，以研究Valsalva推的能量成本，包括和不包括（a）最大手臂和（B）手臂和大腿肌肉等长收缩。 这些观察结果将有助于深入了解与最大伤害风险相关的因素，并应导致更好的预防这些伤害的方法。

Approximately 15% of women sustain pelvic muscle injuries during vaginal birth, demonstrable through magnetic resonance (MR) imaging. Our geometric model suggests the pelvic floor muscles stretch up to 3.3 times their original length during the second stage of birth. Based on MR imaging, histological, studies, and biomechanical modeling, when injury occurs, we hypothesize an initial rupture of the pubic attachment ofthe pubovisceral muscle (Type 1 injury), in some women followed by an avulsion of the pubic attachment of the arcus tendineus levator ani (Type 2 injury). We seek funds to characterize the variation of tissue in these injury zones and document their failure loads. AIM 1 will characterize the morphology and histology of pubovisceral and arcus tendineus tissues, bi-axial material properties where appropriate, and uniaxial failure properties in 30 cadavers. In 20 volunteers, we will use ultrasound elastography to characterize the effect of pregnancy on perineal body elasticity. AIM 2 will use Aim 1 data to refine a subject-specific, 3-D finite element viscohyperelastic biomechanical model of the second stage of labor from Station +2 on. We will test the above hypotheses with regard to the sequence of Type 1/Type 2 injuries, and run parametric studies to determine the biomechanical factors that increase or decrease the risk of Type 1 and Type 2 injuries. We will validate the model with stereophotogrammetric measurements of perineal descent in 10 laboring women. Since maternal exhaustion is a major risk for instrumented delivery and levator muscle injuries, in AIM 3 we will use a repeated measures design to quantify the outcomes in 40 healthy non-pregnant volunteers between 21 and 30 years of age to study the energetic cost of Valsalva pushing with and without (a) maximal arm and (b) arm and thigh muscle isometric contractions. 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.