In vivo assessment of the elastic properties of women’s pelvic floor during pregnancy using shear wave elastography: design and protocol of the ELASTOPELV study

Abstract

Background: Animal studies have reported an increase in pelvic floor muscle stiffness during pregnancy, which might be a protective process against perineal trauma at delivery. Our main objective is to describe the changes in the elastic properties of the pelvic floor muscles (levator ani, external anal sphincter) during human pregnancy using shear wave elastography (SWE) technology. Secondary objectives are as follows: i) to look for specific changes of the pelvic floor muscles compared to peripheral muscles; ii) to determine whether an association between the elastic properties of the levator ani and perineal clinical and B-mode ultrasound measures exists; and iii) to provide explorative data about an association between pelvic floor muscle characteristics and the risk of perineal tears. Methods: Our prospective monocentric study will involve three visits (14-18, 24-28, and 34-38 weeks of pregnancy) and include nulliparous women older than 18 years, with a normal pregnancy and a body mass index (BMI) lower than 35 kg.m − 2. Each visit will consist of a clinical pelvic floor assessment (using the Pelvic Organ Prolapse Quantification system), an ultrasound perineal measure of the anteroposterior hiatal diameter and SWE assessment of the levator ani and the external anal sphincter muscles (at rest, during the Valsalva maneuver and during pelvic floor contraction), and SWE assessment of both the biceps brachii and the gastrocnemius medialis (at rest, extension and contraction). We will collect data about the mode of delivery and the occurrence of perineal tears. We will investigate changes in continuous variables collected using the Friedman test. We will look for an association between the elastic properties of the levator ani muscle and clinical / ultrasound measures using a Spearman test at each trimester. We will investigate the association between the elastic properties of the pelvic floor muscles and perineal tear occurrence using a multivariate analysis with logistic regression. Discussion: This study will provide original in vivo human data about the biomechanical changes of pregnant women's pelvic floor. The results may lead to an individualized risk assessment of perineal trauma at childbirth. Trial registration: This study was registered on https://clinicaltrials.gov on July 26, 2018 (NCT03602196).

Transperineal ultrasound shear-wave elastography is a reliable tool for assessment of the elastic properties of the levator ani muscle in women

“…The principles of ultrasound SWE and the procedure for measuring muscle elastic properties have been widely described and illustrated in previous publications, and specific aspects pertaining to the LAM are described below 11 – 14 .…”

“…For measurements in each condition, the participants lay down in the lithotomy position with an empty bladder. The pubic insertion of the right LAM was identified in B-mode ultrasound with a transperineal approach using the procedure reported by Dietz et al, after which we proceeded to perform the SWE acquisition 11 , 12 , 18 . Before any LAM assessment, the participants performed 2 initial Valsalva maneuvers with biofeedback, in which visible pelvic floor displacements on the B-mode image were shown to the participant on the screen, to prevent LAM coactivation 19 .…”

“…The viscoelastic properties of pelvic floor muscles could be measured using a speculum combined with sensors, i.e., a vaginal probe able to measure the force exerted by the pelvic floor muscles on it 9 , 10 . However, they require an intravaginal intrusive examination, and it remains an indirect measurement on pelvic floor muscles elastic properties (based on the force exerted on the probe/speculum) 2 , 11 .…”

“…In the present study, we investigate inter-day and intra-operator reliability for LAM to validate its use in future prospective studies. We also investigate the intrasession reliability to check if the procedure could be simplified by doing only one single measure instead of 3 consecutives measures 11 . So, the main objective of the present study was to assess the intraoperator intersession reproducibility of ultrasound SWE to measure the LAM elastic properties in women 12 .…”

Advancing frontiers in rheumatic and musculoskeletal imaging

“…The authors found no differences in terms of thickness and vascularity, but significantly reduced stiffness in gout-patients. Furthermore, Gachon et al plan a prospective study on pregnant patients to describe changes in the elastic properties of pelvic floor muscles through elastography providing potentially useful data concerning the risk of perineal tears at childbirth [ 14 ]. Ultrasound is also widely used and strongly recommended as a guidance for several interventional procedures in the musculoskeletal system [ 20 ].…”