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