Main Findings
By mechanically supporting the USL, we were able to temporarily alleviate provoked vulvar pain in some women. These results support our hypothesis and possibly create a new field in the study of PV.
During trial manipulation for USL support, patients reported a significant reduction in pain intensity compared with their baseline pain level. The wide swab probably sufficiently supported USL laxity to restore its ability to mechanically support the nerve plexuses, thereby relieving the pain (Figure S1).
Although the improvement with USL mechanical support was impressive, several patients described no improvement whatsoever in their pain level. These findings are in accordance with the current consensus, suggesting that vulvodynia is associated with different contributing factors.1
In line with this consensus, it is reasonable to suggest that the subjects who reported pain alleviation do, in fact, have USL laxity-associated PV.
Our hypothesis was based not only on our own experimental studies8,9 but also on a general hypothesis of CPPU caused by weakened USLs,6 with CPPU found to be curable either by USL plication11 or by a posterior sling during a randomized trial involving 1420 women.13 The same concept of the role of the USLs was first published in the German literature in 1938 by one of the most famous German gynecologists of the 20th century, Heinrich Martius.14 Martius wrote that in 30% of cases, backaches and pelvic pain were provoked by damage of the paired “ligamenta sacro-uterina” (USL) and the Frankenhauser and sacral ganglia were involved in causing chronic pelvic pain because of the inability of weakened USLs to support them.14
The mechanism by which strengthening the USLs in women without overt pelvic organ prolapse alleviates vestibular sensitivity is consistent with that previously proposed (Figure S1). 5,6,8,9,14Lax USLs cannot mechanically support the nerve plexuses. Furthermore, vulvodynia may be only one phenotype of T10-L2 and S2-4 referred nerve pain. Nevertheless, it remains unknown why some patients did not experience pain relief from USL mechanical support by the swab. A method that provides broader support to include both USLs (such as the lower blade of a bivalve speculum) may, in fact, alleviate pain in more women.14 This was not an option during our study; however, because the handle of the speculum covered the vestibule and prevented Q-tip testing, the device had to be sufficiently narrow to be inserted through the allodynic vulvar vestibule.
Our method of USL support may further support an already established associated factor of PV, namely, musculoskeletal dysfunction such as pelvic muscle overactivity, myofascial changes, and biomechanical changes.1,4 It has been repeatedly shown that physical therapy is helpful for alleviating some cases of PV.4Musculoskeletal dysfunction of the pelvic muscles can be caused by USL laxity. It has been demonstrated by video, X-rays, myograms, and electromyography15,16 that three oppositely acting directional forces, forward, backward, and downward, act against pubourethral ligaments anteriorly and USLs posteriorly to control bladder continence and evacuation. These forces are equally balanced in the region of the bladder neck.17 If USLs are loose, then the posterior forces weaken and the system becomes unbalanced; the forward force (the anterior portion of pubococcygeus muscles) overcompensates by contracting harder to the extent that it can narrow the urethra.17 These are the “overactive” muscles addressed by physical therapy.4 These findings17,18 adequately explain the link between our hypothesis and pelvic muscle dysfunction.1,4