Department of Biomedical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, MI 48109, United States.
Department of Mechanical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, MI 48109, United States.
J Mech Behav Biomed Mater. 2018 Mar;79:213-218. doi: 10.1016/j.jmbbm.2017.12.025. Epub 2017 Dec 30.
Remarkable changes must occur in the pelvic floor muscles and tissues comprising the birth canal to allow vaginal delivery. Despite these preparatory adaptations, approximately 13% of women who deliver vaginally for the first time (nulliparas) sustain tears near the origin of the pubovisceral muscle (PVM) which can result in pelvic organ prolapse later in life. To investigate why these tears occur, it is necessary to quantify the viscoelastic behavior of the term pregnant human birth canal. The goal of this study was to quantify the in vivo material properties of the human birth canal, in situ, during the first stage of labor and compare them to published animal data. The results show that pregnant human, ovine and squirrel monkey birth canal tissue can be characterized by the same set of constitutive relations; the interspecies differences were primarily explained by the long time constant, τ, with its values of 555s, 1110s, and 2777s, respectively. Quantification of these viscoelastic properties should allow for improved accuracy of computer models aimed at understanding birth-related injuries.
为了允许阴道分娩，包括分娩通道在内的骨盆底肌肉和组织必须发生显著变化。尽管有这些预备性适应，但大约 13%初次阴道分娩的女性（初产妇）在耻骨直肠肌（pubovisceral muscle，PVM）起源处附近发生撕裂，这可能导致日后发生盆腔器官脱垂。为了探究这些撕裂发生的原因，有必要量化足月妊娠女性分娩通道的黏弹性行为。本研究的目的是量化分娩第一阶段活体人体分娩通道的原位材料特性，并将其与已发表的动物数据进行比较。结果表明，妊娠人类、绵羊和松鼠猴的分娩通道组织可以用相同的本构关系来描述；种间差异主要由时间常数 τ 来解释，其值分别为 555s、1110s 和 2777s。对这些黏弹性特性的量化应该可以提高旨在理解与分娩相关损伤的计算机模型的准确性。
