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Concurrent Validity of Noninvasive Coccygeal Motion Palpation and Transabdominal Ultrasound Imaging in the Assessment of Pelvic Floor Function in Women

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No gold standard exists for assessing pelvic floor muscle (PFM) function. However, a significant correlation exists between digital palpation and transabdominal ultrasound imaging (TAUS), with studies indicating that the coccyx moves during contractions.


To determine concurrent validity of external coccyx motion palpation (CMP) versus TAUS to identify the former's validity in assessing PFM function.

Study Design:

A cross-sectional observational study.


Sixty-four women were screened. Those who could perform a PFM contraction were enrolled (n = 37; mean 31.5 years). A single investigator was assigned to either TAUS or CMP. Participants were randomly assigned to perform either a PFM contraction, bearing down, or nothing under randomly assigned testing positions: standing, sitting, and side-lying while simultaneous TAUS and CMP occurred. Investigators were blinded to each other's assessment, and participant-assigned tasks. Participants were blinded to TAUS.


Sensitivity and specificity were 94% and 79%, respectively, for CMP versus TAUS. χ2 tests and phi coefficient (Φ) revealed a significant strong relationship between TAUS and CMP across positions: standing χ2(1, n = 37) = 17.87, P < .001, Φ = 0.7; sitting χ2(1, n = 37) = 15.79, P < .001, Φ = 0.65; and side-lying χ2(1, n = 37) = 17.88, P < .001, Φ = 0.7, respectively.


CMP is a valid screening method that can be used by all clinicians. It may decrease unnecessary internal digital assessment while being more acceptable to women who decline an internal digital assessment, or in pregnant women for whom a digital assessment may be contraindicated.

We have included a Video Abstract that highlights our ultrasound cine-loops and findings in our article (see the Video Abstract, Supplemental Digital Content, available at:

Keywords: incontinence; levator ani; pelvic floor muscle training

Document Type: Research Article

Publication date: December 1, 2020

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