Modelling Levator Ani Mechanics During the Second Stage of Labour

Abstract

This thesis presents a modelling framework that quantitatively analyses the mechanical behaviour of the levator ani (LA) muscle during the second stage of labour. This modelling framework would enable the identification of risk factors (for muscle birth simulations. Both factors showed marked effects on the mechanical response of the LA muscle. The dorsal-caudal aspect of the LA muscle and the insertions to the pubis were identified as high risk areas of muscle damage, due to large stretches (>2.5) predicted by the model. LA muscle trauma at these locations has also been observed clinically. This modelling framework was then applied to simulate the use of an intra- vaginal device test in order to investigate the passive muscle properties in control and high impact, frequent intense training (HIFIT) women. Results of this study suggest no difference in the passive stiffness between these two groups, which is in contrast to previous findings based on a simplified conceptual model. However, the relative difference in the average force was comparable with previous results. The study demonstrated the ability of the modelling framework to quantitatively interpret clinical data in silico.