Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
Biomech Model Mechanobiol. 2011 Jul;10(4):485-94. doi: 10.1007/s10237-010-0249-z. Epub 2010 Aug 24.
Pelvic floor dysfunction and pelvic organ prolapse have been associated with damage to the levator ani (LA) muscle, but the exact mechanisms linking them remain unknown. It has been postulated that factors such as vaginal birth and ageing may contribute to long-term, irreversible LA muscle damage. To investigate the biomechanical significance of the LA muscle during childbirth, researchers and clinicians have used finite element models to simulate the second stage of labour. One of the challenges is to represent the anisotropic mechanical response of the LA muscle. In this study, we investigated the effects of anisotropy by varying the relative stiffness between the fibre and the matrix components, whilst maintaining the same overall stress-strain response in the fibre direction. A foetal skull was passed through two pelvic floor models, which incorporated the LA muscle with different anisotropy ratios. Results showed a substantial decrease in the magnitude of the force required for delivery as the fibre anisotropy was increased. The anisotropy ratio markedly affected the mechanical response of the LA muscle during a simulated vaginal delivery. It is apparent that we need to obtain experimental data on muscle mechanics in order to better approximate the LA muscle mechanical properties for quantitative analysis. These models may advance our understanding of the injury mechanisms of pelvic floor during childbirth.
盆底功能障碍和盆腔器官脱垂与肛提肌 (LA) 损伤有关，但它们之间的确切联系机制尚不清楚。有人推测，阴道分娩和衰老等因素可能导致 LA 肌肉的长期、不可逆转的损伤。为了研究分娩过程中 LA 肌肉的生物力学意义，研究人员和临床医生使用有限元模型来模拟第二产程。其中一个挑战是表示 LA 肌肉的各向异性力学响应。在这项研究中，我们通过改变纤维和基质成分之间的相对刚度来研究各向异性的影响，同时保持纤维方向上相同的整体应力-应变响应。一个胎儿颅骨穿过两个包含不同各向异性比的 LA 肌肉的盆底模型。结果表明，随着纤维各向异性的增加，分娩所需的力的大小显著降低。各向异性比显著影响了模拟阴道分娩过程中 LA 肌肉的力学响应。显然，我们需要获得肌肉力学的实验数据，以便更好地近似 LA 肌肉的力学特性进行定量分析。这些模型可能有助于我们更好地理解分娩过程中盆底损伤的机制。
