Pelvic floor dysfunction, more specifically increased pelvic floor stiffness, has been reported in women with provoked vestibulodynia (PVD) [1,2]. However, the available evidence is derived from global pelvic floor measurements. Assessment methods that capture values from individual muscles or specific pelvic floor structures remain limited, due to the constraints of currently available assessment tools. This limits our understanding of the involvement of specific pelvic floor structures in chronic pelvic pain and hinders the development of more targeted treatment approaches. Novel assessment methods incorporating elastography-derived strain metrics may provide new insight into tissue mechanical properties at the level of individual pelvic floor structures, allowing a more detailed evaluation than previously possible. Therefore, the aim of this study was to compare strain metrics obtained from individual pelvic floor structures between women with PVD and pain-free individuals.

Thirty-six women with PVD and 36 pain-free women (mean age 25±4.96 years) participated in this study. Pelvic floor structures (puborectalis muscle, transverse perineal muscle, obturator internus muscle, and perineal body) were evaluated using a novel assessment method developed by our team. Elastography strain metrics (cumulated major [CMajor] and minor [CMinor] strains) were quantified from 2D radiofrequency ultrasound images (Terason uSmart 3200T NexGen, Burlington, VT, USA) acquired during controlled tissue displacement, as required for strain analysis. For the assessment of the perineal body, transverse perineal muscle, and puborectalis muscle, a linear array transducer (15L4A, 4.0-15.0 MHz) was placed on the perineum, and a Foley catheter was inserted intravaginally and inflated with water (15 mL) to induce passive displacement. For the assessment of the obturator internus muscle, participants were positioned in lateral decubitus, and the ultrasound probe was placed at the level of the obturator foramen on the side of the limb resting on the examination table. The lower leg was then passively moved from 0 to 30 degrees to induce hip internal rotation. Image sequences of all assessed structures were recorded as B-mode and radiofrequency cine loops, and data were extracted during post-processing using a customized MATLAB script (The MathWorks, Natick, MA, USA). Pelvic floor structures were outlined on B-mode images, and marked regions of interest were used to compute CMajor and CMinor. Strain metrics were then compared between groups using a linear mixed-effects model.

CMajor and CMinor strains differed between women with PVD and pain-free controls. In the perineal body, strain values were higher in controls than in the PVD group (β=1.204, 95% CI 1.072–1.352, p=.002 for CMajor; β=1.191, 95% CI 1.079–1.315, p=.001 for CMinor). Similar results were observed for the transverse perineal muscle (β=1.295, 95% CI 1.145–1.464, p<.001 for CMajor; β=1.195, 95% CI 1.068–1.336, p=.002 for CMinor). No statistically significant between-group differences were observed for the obturator internus or puborectalis muscles.

Lower strain values in women with PVD may suggest greater stiffness of the perineal body and transverse perineal muscle, providing novel evidence of their involvement in this condition and informing future treatment strategies that may specifically target these structures. The absence of statistically significant differences for the puborectalis and obturator internus muscles may be related to their deeper anatomical location, which could have limited the induced displacement and consequently affected strain values.

By employing a novel assessment method allowing the capture of strain metrics from individual pelvic floor structures, it was shown that women with PVD exhibit lower strain values in the perineal body and the transverse perineal muscle. These findings provide new insight suggesting increased pelvic floor tissue stiffness in this condition.

Morin M, Binik YM, Bourbonnais D, Khalife S, Ouellet S, Bergeron S. Heightened Pelvic Floor Muscle Tone and Altered Contractility in Women With Provoked Vestibulodynia. J Sex Med. Apr 2017;14(4):592-600. doi:10.1016/j.jsxm.2017.02.012
Kadah S, Soh S-E, Morin M, Schneider M, Heron E, Frawley H. Is there a difference in pelvic floor muscle tone between women with and without pelvic pain? A systematic review and meta-analysis. The Journal of Sexual Medicine. 2023;20(1):65-96. doi:10.1093/jsxmed/qdac002