Application of a new method in the study of pelvic floor muscle passive properties in continent women

Abstract 

The aim of this study was to present a new methodology for evaluating the pelvic floor muscle (PFM) passive properties. The properties were assessed in 13 continent women using an intra-vaginal dynamometric speculum and EMG (to ensure the subjects were relaxed) in four different conditions: (1) forces recorded at minimal aperture (initial passive resistance); (2) passive resistance at maximal aperture; (3) forces and passive elastic stiffness (PES) evaluated during five lengthening and shortening cycles; and (4) percentage loss of resistance after 1min of sustained stretch. The PFMs and surrounding tissues were stretched, at constant speed, by increasing the vaginal antero-posterior diameter; different apertures were considered. Hysteresis was also calculated. The procedure was deemed acceptable by all participants. The median passive forces recorded ranged from 0.54N (interquartile range 1.52) for minimal aperture to 8.45N (interquartile range 7.10) for maximal aperture while the corresponding median PES values were 0.17N/mm (interquartile range 0.28) and 0.67N/mm (interquartile range 0.60). Median hysteresis was 17.24N∗mm (interquartile range 35.60) and the median percentage of force losses was 11.17% (interquartile range 13.33). This original approach to evaluating the PFM passive properties is very promising for providing better insight into the patho-physiology of stress urinary incontinence and pinpointing conservative treatment mechanisms.

Keywords: Levator ani, Resting forces, Stiffness, Tone, Dynamometry, Continence