Right usual compulsory (for me) disclaimer. I am a med student - so please do not take my comments as authoritative. I'm going hazard an answer here partly because I have some soul source dilators myself, and partly because I am just revising female reproductive anatomy for my exam on friday and answering this question has driven me go and look at the anatomical details again...
So I apologise for the fact that unless you are an anatomy anorak the last part of this answer may not be of much interest. That said I personally find it fascinating
and it literally fills me with awe that someone figured this all out back in the early days.
I'm not a supporn girl because he was only a little boy when I had my corrective surgery, but I do have the same two soul-source dilators as you because I purchased them when my nearly 30 year old NHS set started to fall apart due to old age.
I don't dilate very often, but keep them handy because once in a while I like to check that all the inches are still there. – There are dots on the side and they represent the depth – the last one is 5.5in which would be standard depth – the middle notch would be 7 inches but remember to be at that depth that notch should be in the vaginal tube and not just between the labia... in other words it should be in beyond the vestibular opening and urethra, and not merely between your labia! That will make at least half an inch to an inch in difference.
Most people who think they have 7 inches actually only have about 6 because they measure from the wrong point. However as 6 inches is a good 2.5 inches longer than a natal female in un-stretched position that's not too bad really. The female vagina isn't actually that long – it just stretches very very easily. (well up to a point... of course if you try to deliver a babies head through it then you will find the limit of that - and may end up with an episiotomy scar (which incidentally I quite accidentally have... but that's another story!)
Normal result for post SRS depth are anything between 4 and 6 inches, and often the limit is not your tissue but the dimensions of your pubic opening and the resultant position and insertion angle of the neovaginal canal. If you have a female type pubic symphysis with a wide arch of greater than 90 degrees you will have a better positioned vaginal opening and a slightly better chance of a good depth. It does also depend slightly on how stretchy your tissue is – mine fairly like a natal in that whilst the relaxed length is nothing spectacular it stretches readily and thus can easily accommodate the full length of the biggest dilator (that extra stretchy tissue may possibly be an unexpected bonus from my having been intersexed).
The curved shape at the end is because a normal vaginal canal would be slightly ante-flexed by the cervix of a normal anteverted uterus. The uterus would normally lie superior and posterior to the bladder with the fundus palpable just above the pubic symphysis. By curving slightly the soul-source emulates the resultant vaginal shape. In terms of dynamic dilation obviously you can't twist them – but you can push them in and out ok. They should insert curve side up.
The anatomy involved in the construction of a neovagina is fascinating.
In a neovagina the uterine suspensory ligaments which would normally help to prevent prolapse will not exist. Thus suspension will rely on a knotting of the peritoneal faschia – possibly with the remains of the now inverted bucks fascia from the penis. The problem is the male lacks one of the two deep peritoneal pouches that would be found in the female. Females have a utero-vesical pouch and a utero rectal pouch –this give plenty of spare material with which to form a pseudo suspensory ligament for the vagina following hysterectomy.
In trans patients however there will only be the one recto-vesical pouch and thus there is not as much peritoneal membrane with which to work. The challenge for the surgeon is therefore to position the vaginal canal at an angle which both allows reasonable depth – but also allows the construction of an artificial suspensory ligament so that it does not prolapse post surgically.
Anyway - all of that is by way of saying no they aren't curved because the male pelvis is narrower - that is the way things should be, and the other dilators are slightly in accurate - but that won't matter for a natal female because the shape of a female vagina is established by all the normal suspension of the uterus. Thus the vagina is held in the right attitude because it is anchored well at both ends...
Well done if you waded through all that - and if there are any anatomists among us - please tell me if I got it right.
