How well can levator ani muscle morphology on 3D pelvic floor ultrasound predict the levator ani muscle function?

INTRODUCTION AND HYPOTHESIS: The aim of our study was to assess the performance of levator ani muscle deficiency (LAD) evaluated by 3D endovaginal ultrasound (EVUS) to detect pelvic floor muscle function as assessed by digital examination.
METHODS: This cross-sectional study was conducted among 77 patients referred to our urogynecology clinic for pelvic floor dysfunction symptoms. Patients underwent physical examinations including digital pelvic muscle strength assessment using the Modified Oxford scale (MOS). EVUS volumes were evaluated and levator ani muscles were scored according to a validated LAD scoring system. MOS scores were categorized as nonfunctional (scores 0-1) and functional (scores 2-5).
RESULTS: Mean age of participants was 56 (SD ± 12.5) and 71% were menopausal. Overall, 32.5% had nonfunctional muscle strength and 44.2% were classified as having significant LAD. LAD identified by ultrasound had a sensitivity of 60% (95% CI 41 -79%) for detecting nonfunctional muscle and a specificity of 63% (95% CI 50 -77%) for detecting functional muscle. Overall, LAD demonstrated fair ability to discriminate between patients with and those without poor muscle function (area under the ROC curve = 0.70 [95% CI 0.58-0.83]). Among patients with an LAD score of 16-18, representing almost total muscle avulsion, 70% had nonfunctional MOS scores, whereas in patients with normal/minimal LAD (scores of 0-4), 89.5% had functional MOS scores.
CONCLUSIONS: Levator ani deficiency and MOS scales were moderately negatively correlated. Among patients with normal morphology or the most severe muscle deficiency, LAD scores can identify the majority of patients with functional or nonfunctional MOS scores respectively.