Vaginal delivery poses a significant risk of injury to the pelvic floor muscles (PFMs). In one-third of women, the stretching of these muscles is so extensive that it results in avulsion injury (i.e., a disconnection of the levator ani muscle from its attachment to the pubic symphysis). The severity of avulsion can be categorized as unilateral or bilateral, depending on whether one or both sides of the levator ani are affected. This common injury notably increases the risk and severity of post-partum urinary incontinence (UI) [1]. Although multimodal pelvic floor physiotherapy is recognized as a first-line treatment for UI [2], the impact of the severity of avulsion on treatment response remains unclear. This study aimed to evaluate the association between the severity of avulsion injury and the frequency of UI episodes in postpartum women after completing a multimodal physiotherapy program.

This study is a secondary analysis of a larger multicenter randomized controlled trial that evaluated the efficacy of multimodal physiotherapy for UI, compared to a control group, in women with levator ani muscle avulsion. Women in the control group were offered the same physiotherapy treatment program after completing their participation in the parent study. Data collected from both groups at baseline and after completing the 12 weekly physiotherapy sessions by a blinded assessor were considered in this analysis. Women aged 18-45 years suffering from stress or mixed UI participated in the study. The intervention consisted of 12 weekly multimodal physiotherapy sessions, including education, PFM training with biofeedback and home exercises. The diagnosis and severity of avulsion (unilateral and bilateral) were assessed at baseline using transperineal 4D ultrasound following a validated methodology [3]. Frequency of UI episodes was evaluated using a seven-day bladder diary. Based on the existing literature, covariates potentially impacting treatment response were evaluated at baseline and included: PFM stiffness, strength endurance (assessed with an intra-vaginal dynamometer), morphometry at rest and during maximal PFM contraction such as the bladder neck position and the hiatal dimensions (evaluated with transperineal 4D ultrasound), anthropometric measures (i.e. body mass index, waist to hip ratio), as well as sociodemographic and other health-related characteristics (i.e. age, number of pregnancies, etc.). Exploratory linear regressions were performed to assess the association between each covariate and the frequency of UI episode post-treatment, adjusting for baseline UI (p<.10). A multivariable linear regression was then computed to assess the association between the severity of avulsion and treatment response (i.e frequency of UI episodes post-treatment) while accounting for baseline UI and the significant covariates identified in the exploratory analyses.

Of the 126 women included (75 unilateral and 51 bilateral avulsions), 107 participants completed the study. As shown in Table 1, the multivariable linear regression revealed that the severity of avulsion was not significantly associated with the frequency of UI episode at post-treatment (B=0.244, 95%CI[-1.891, 2.379], p=.821). Waist-to-hip ratio and frequency of UI episode at baseline were significantly associated with the frequency of UI episodes post-treatment.

This study is the first to evaluate the impact of avulsion severity on response to multimodal physiotherapy treatment. The findings indicate that the severity of avulsion injury was not significantly associated with treatment response. However, greater UI severity at baseline and a higher waist-to-hip ratio (i.e., apple-shaped body type) were associated with poorer treatment response (i.e. a higher frequency of UI episodes post-treatment).

Findings showed that the severity of levator ani avulsion is not associated with treatment response, reinforcing that multimodal physiotherapy should be offered as a non-invasive first-line treatment to all women with UI, regardless of obstetrical injury extent.

van Delft KW, Thakar R, Sultan AH, IntHout J, Kluivers KB. The natural history of levator avulsion one year following childbirth: a prospective study. BJOG. 2015;122(9):1266-1273. doi:10.1111/1471-0528.13223
Cardozo L, Rovner E, Wagg , Wein A, Abrams P. Incontinence: 7th International Consultation on Incontinence. International Continence Society; 2023.
Dietz, H. P., M. J. Bernardo, A. Kirby and K. L. Shek (2011). "Minimal criteria for the diagnosis of avulsion of the puborectalis muscle by tomographic ultrasound." Int Urogynecol J 22(6): 699-704.