Manoogian Sarah, Mcnally Craig, Calloway Britt, Duma Stefan
Virginia Tech-Wake Forest Center for Injury Biomechanics, Blacksburg, VA, USA.
Biomed Sci Instrum. 2007;43:230-5.
Placental abruption accounts for 50% to 70% of fetal losses in motor vehicle crashes. Since automobile crashes are the leading cause of traumatic fetal injury mortality in the United States, research of this injury mechanism is important. Before research can adequately evaluate current and future restraint designs, a detailed model of the pregnant uterine tissues is necessary. The purpose of this study is to develop a methodology for testing the pregnant uterus in biaxial tension at a rate normally seen in a motor vehicle crash. Since the majority of previous biaxial work has established methods for quasi-static testing, this paper combines previous research and new methods to develop a custom designed system to strain the tissue at a dynamic rate. Load cells and optical markers are used for calculating stress strain curves of the perpendicular loading axes. Results for this methodology show images of a tissue specimen loaded and a finite verification of the optical strain measurement. The biaxial test system dynamically pulls the tissue to failure with synchronous motion of four tissue grips that are rigidly coupled to the tissue specimen. The test device models in situ loading conditions of the pregnant uterus and overcomes previous limitations of biaxial testing. A non-contact method of measuring strains combined with data reduction to resolve the stresses in two directions provides the information necessary to develop a three dimensional constitutive model of the material. Moreover, future research can apply this method to other soft tissues with similar in situ loading conditions.
胎盘早剥占机动车碰撞事故中胎儿死亡的50%至70%。由于汽车碰撞是美国创伤性胎儿损伤死亡的主要原因，因此对这种损伤机制的研究很重要。在研究能够充分评估当前和未来的约束设计之前，有必要建立一个详细的妊娠子宫组织模型。本研究的目的是开发一种方法，以机动车碰撞中常见的速率对妊娠子宫进行双轴拉伸测试。由于之前的大多数双轴研究都建立了准静态测试方法，本文结合先前的研究和新方法，开发了一种定制设计的系统，以动态速率对组织施加应变。载荷传感器和光学标记用于计算垂直加载轴的应力应变曲线。该方法的结果显示了加载的组织标本图像以及光学应变测量的有限验证。双轴测试系统通过与组织标本刚性连接的四个组织夹具的同步运动，动态地将组织拉伸至破坏。该测试装置模拟了妊娠子宫的原位加载条件，克服了先前双轴测试的局限性。一种测量应变的非接触方法与数据简化相结合，以解析两个方向上的应力，提供了开发材料三维本构模型所需的信息。此外，未来的研究可以将这种方法应用于具有类似原位加载条件的其他软组织。
