Does size matter? Perineometer and digital examination of a model levator hiatus

Abstract

Introduction Evaluation of the female pelvic floor muscles is commonly carried out with digital examination and assigning a modified Oxford scale score or vaginal manometry. Racial differences can influence the size of the levator hiatus (LH) with “black” or African nulliparous women having a significantly larger LH compared to Caucasian women. The aim of this study was to assess the impact of LH size on manometry readings of simulated pelvic floor muscle contractions (PFMCs) using a small and large model LH. Methods Small and large LH models were created using published data for size. Inflation of a pressure cuff placed circumferentially in the LH model represented a simulated PFMC. The models were examined in a supine position by three examiners and a perineometer twice each at varying simulated PFMC strength. Results Positive correlation was found between increasing simulated PFMC strength with a higher Oxford score following digital examination and manometry readings for both the small (rs = .87, rs = .98) and large (rs = .95, rs = .87) models. There was good to excellent inter and intraobserver correlation for digital assessment of both models. The manometry measurements showed a much larger incremental rise from baseline in the small model compared with the large model (P < .05). Conclusion This study demonstrates that perineometer readings are affected by natural variations in LH size and PFMC strength. Therefore improvement to pelvic floor strength cannot be interpreted and measurements cannot be compared with others unless the LH size is known or digital examination is carried out.

Levator hiatal ballooning prevalence in pelvic organ prolapse patients and its relation to levator ani muscle strength

“…Therefore, smaller levator hiatus size is associated with stronger pelvic floor muscle contractions. 10 There is a significant correlation between the LAM strength measurement using both digital and perineometer on all groups. Moreover, a lower perineometer result was observed in the ballooning group compared to the non-ballooning group.…”

“…A study by Tailor et al (2020) using a pelvic floor muscle model found that the size of the levator hiatus affects the strength of pelvic floor muscle contraction. 10 Using the same amount of force, the strength of pelvic floor muscle contraction would be lower in the population with a large levator hiatus than in the population with a small levator hiatus. This phenomenon would result in lower measurement results on the perineometer.…”