Anatomic and functional evaluation of the levator ani muscle after an obstetric anal sphincter injury

Purpose To study the relationship between symptoms of anal incontinence (AI) and the anatomy and functionality of the levator ani muscle in women with a history of obstetric anal sphincter injury (OASI). Methods This is a cohort study including patients with OASI from 2013 to 2016. Patients were assessed by a physical examination, endoanal ultrasound using Starck Scale, perineometry and 4D transperineal ultrasound. AI in all patients was measured with the Wexner scale. Correlation between variables has been analyzed in these patients. Results 72 patients were analyzed: 28 with a IIIA degree tear, 26 with a IIIB, 13 with a IIIC and 5 with a IV. 38 patients showed a residual anal sphincter (AS) defect on endoanal ultrasound with an average Starck score of 6.5 ± 3.7. 21 patients expressed AI, with an average Wexner score of 4.1 ± 2.4. In 27 (37.5%) patients, a levator ani avulsion was observed: 17 unilateral and 10 bilateral. Patients with a levator ani defect had weaker pelvic floor muscle (PFM) function. These differences were statistically significant with perineometry ( p = 0.01 and p = 0.03) but not for the Oxford test ( p = 0.08). Patients with a residual AS defect as well as an injury to the levator ani muscle expressed greater AI symptomatology than patients with residual sphincter injury who maintain the integrity of the levator ani: Wexner 4.9 0.9 vs 3.3 1 ( p = 0.02). Conclusions The PFM has correlation with AI symptom development in patients with a history of OASI. Therefore, we suggest a key role of anatomical and functional assessments of the levator ani muscle in these patients.