So let's enlist few important points in relation to the ischial spines.
Ischial spines can be generally be palpated at about a finger-length into the vagina, at 4 & 8o'clock.
They are felt as bony prominences and their palpation may cause a little discomfort to the patient.
These spines serve as a landmark for:
1) Engagement of Fetal Head.(Most commonly used for determining the Fetal Station during labor.
Ischial spines are considered as Station0)
2) Internal Rotation of the fetal head.
3) Pudendal Nerve Block.
4) External os.
5) Obstetric Curve (J shaped) takes forward curve at this level.
6) Insertion of levator Ani.
7) Plane of least pelvic dimension.
8) Ring pessary is kept at the level of ischial spines.
These are the few things I know about at the level of the Ischial spines.
Do let me know some additional points you know of, to add to the list.
Let's learn Together!