Apical Ligament and Levator Muscle Interactions in Pelvic Organ Prolapse

阴道分娩使妇女发生脱垂的风险增加8倍，这种情况每年导致20万例手术，10年后再手术率高达25%。出现脱垂的两个主要原因是：1)宫颈和阴道上部下降（根尖下降），涉及枢机韧带/子宫骶韧带；2)阴道分娩时提肛肌的神经肌肉损伤。

Vaginal birth confers an 8-fold increase in the risk for a woman developing prolapse, a condition that results in 200,000 operations per year and carries up to a 25% reoperation rate at 10 years. Two primary causes for prolapse have emerged: 1) descent of the cervix and upper vagina (apical descent) involving the cardinal/uterosacral ligaments, and 2) neuromuscular damage to the levator ani muscles during vaginal birth. The relationship between these factors is unknown. It is the overall goal of our research to discover the basic mechanism whereby muscle and ligament failure interact producing prolapse. Our theoretical work suggests the working hypothesis that levator damage leads to opening of the levator urogenital hiatus and results in exposure of the vaginal wall to a pressure differential that pulls downward on the apical supports. Lack of data concerning ligament stiffness prevents a quantitative understanding of these relationships. We will recruit and test 50 asymptomatic volunteers and 50 women with pelvic organ prolapse to accomplish the following aims. Aim 1 will use a new servoactuator device to measure the in vivo ligament force-displacement behavior ("stiffness") to determine the role of different ligament properties in prolapse. Aim 2 will make static and dynamic MRI images and clinical pelvic floor measurements to establish the relative contribution to apical descent by a) muscle impairment b) ligament properties. Aim 3 will create subject-specific 3D models of the cardinal and uterosacral ligaments, which will be used to and determine the measurement differences in cardinal and uterosacral elongation in apical descent. The results of this study will provide data that can lead to clinically relevant tests to, for example, identify which patients need an operation to support the apex. It will also provide the much needed data, validating an overall disease model concerning interactions between ligament support and muscle damage. This research will be helpful in developing strategies for improved prevention and treatment selection and a better understanding of why muscle damage at birth causes prolapse later in life.