Four‐dimensional translabial ultrasound concordance with digital palpation and surface electromyography during dynamic pelvic floor muscles assessment: A cross‐sectional study

AIM: To investigate whether pelvic floor muscle (PFM) morphological changes obtained through four-dimensional translabial ultrasound (4D TLUS) correlate with a PFM contraction as evaluated by digital palpation and PFM electromyographic activity evaluated by surface electromyography (sEMG). The secondary objective was to investigate which ultrasound parameter is more strongly associated with digital palpation. METHODS: This cross-sectional study included 210 women and their PFMs were evaluated by digital palpation (graded according to the Modified Oxford Scale), sEMG and 4D TLUS. Offline analysis of ultrasound volume datasets was performed for measuring the change in levator plate angle, bladder neck elevation, hiatal area narrowing, puborectalis strain, and puborectalis muscle thickness at rest and during PFM contraction. Statistical analysis included Kruskal-Wallis, Dunn, and Spearman's tests in addition to univariate and multivariate logistic regression, adopting a significance level of 5%. RESULTS: A weak but significant correlation between the change in levator plate angle and sEMG (P = .04; r = 0.14) was found. All 4D TLUS measurements, except the puborectalis muscle thickness, significantly correlated with digital palpation (P < .0001); with the puborectalis strain and the change in levator plate angle having the strongest combined parameters associated with digital palpation (R(2) = 21.77%), despite the low coefficient of determination. CONCLUSION: We found that 4D TLUS significantly correlates with digital palpation and sEMG, being the change in the levator plate angle the parameter that best correlates with both methods. While digital palpation is essential during a PFM functional assessment, 4D TLUS is recommended as a beneficial noninvasive clinical tool for a more in-depth evaluation.