Hello all this is Dr Alsup and we will be talking about the piriformis muscle and how it can help us
organize some of the neurovasculature in the deep posterior hip region. Specifically we are
talking about the piriformis muscle after it's exited the greater sciatic foramen on its way to
the greater trochanter so that greater sciatic foramen is an important component here as well.
So there is quite a bit of structures exiting the greater sciatic foramen that had originated in the
pelvis and so we're going to talk through some of these. There will be multiple branches of the
sacral plexus as you can see here coming out from these anterior sacral foramina and these branches
will exit the greater sciatic foramen in order to reach specific regions of the lower limb, as
the sacral plexus is the prominent supply for the lower limb other than the anterior medial thigh.
Additionally some branches of the internal iliac artery will also exit the greater sciatic foramen
the majority of the branches of the internal iliac will supply pelvic viscera but there are
gluteal arteries that are branches of the internal iliac as well see here we go superior gluteal
or and the inferior gluteal. So you have all this neurovasculature traversing this area,
so here's that greater sciatic notch with the ligaments it'll be the greater sciatic foramen
it would be right around this region here, so you have all this neurovascular traversing
the region in addition you will have a muscle which is your piriformis muscle.
It will traverse the greater sciatic foramen and its distal tendon will insert on the
greater trochanter of the femur. And having a muscle belly here so having that to be able to
distinguish from the neurovasculature can really help serve as an important landmark on getting
organized in this region and being able to differentiate between the neurovasculature.
So often times you hear this referred to as "the key to the hip" and you will certainly hear me refer to
it as "the key to the hip" when I am dissecting this area I always try to locate the piriformis first
and that helps organize me for the next step so if you're looking here, here is the piriformis
muscle belly and then you can see the tendon heading towards the greater trochanter right here.
All right so and the greater sciatic notch would be right around this region here. Any
of the neurovasculature that you can see coming out or visible superior to the piriformis is the
superior gluteal or gluteal neurovasculature so any of this right here are branches of that
superior gluteal neurovasculature. Now take a moment and think what does the superior gluteal
neurovasculature supply what does it innervate? The gluteus medius and minimus so this is going
to be important in terms of those muscles. There is considerably more neurovasculature located
inferior to the piriformis muscle, more than we will discuss here but there are three major
things I want to note. The first one or major one is the sciatic nerve and this whole thing right
here is the sciatic nerve. It is an impressive nerve it is I always enjoy watching students
locate the sciatic nerve and dissection as it is so impressive as you would expect the biggest
nerve in the body to be, but you can see it exiting and descending inferior to the piriformis muscle.
Right next to it right here you can see the inferior gluteal neurovasculature will also
exit inferior to the piriformis and travel as a unit typically if you're in this type
of dissection as you see here it's been cut because the gluteus maximus has been reflected in
this case it's actually been removed so it makes sense that this would be cut because that's what's
supplying the gluteus maximus. Additionally and not visible in this image will be the pudendal nerve
and internal pudendal artery which also exits the greater sciatic foramen inferior to the piriformis
before almost immediately recurring backwards towards the pelvis to innervate the perineum.
All right excellent we have reached the summary slide and hopefully you are convinced as to why
the piriformis muscle is "the key to the hip" and the basic pattern of neurovasculature organization
around the piriformis. Thank you for your time and attention and have a great rest of your day