hello and welcome back to another Anatomy tutorial today we're going to be looking at the anatomy of the pelvis by looking specifically at a pelvic radiograph now when we look at the pelvis itself we can see that we have a right and a left pelvic bone fusing centrally at the pubic symphysis and separated posteriorly by our sacrum now these pelvic bones actually develop in three different segments if we have a look at this x-ray we can see the three separate segments developing which will eventually fuse to form one pelvic bone we've got our ilium here making up our iliac crest at the top of the pelvis here posteriorly we've got our ischium and anteriorly we've got our pubis these three bones also fuse to form our acetabulum which is where our femur will articulate creating our hip joint now as always when we're looking at a radiograph it's good to have a conceptual or at least a 3D understanding of the anatomy so if we have a look at this 3D rendered CT of the pelvis we can see those pelvic bones here articulating with our femur creating our hip joint and our sacrum separating those pelvic bones posteriorly we have our fourth and our fifth lumbar vertebrae here with the transverse processes our intervertebral disc and the L5 vertebra the fifth lumbar vertebra articulates with our sacrum here we can see our sacrum has a broad base superiorly heading down towards the sacral Apex inferiority at the apex of the sacrum we have these small bones here known as the coccyx or coccygeal bones and our sacrum has these holes or foramina anteriorly which are anterior sacral foramina the sacrum curves is a concave shape like that and superiorly on the sacrum we have this bony outcropping known as the sacral Promontory and that makes this distance here the AP distance quite narrow within the pelvis I'll say call Ayla then spread out laterally towards our s i joint our sacroiliac joints both right and left sacroiliac joints we can see our iliac Wings Fanning out laterally here with our iliac crest and we can see this bony outcropping here which is known as the anterior superior iliac spine and below that is our anterior inferior iliac spine we can see that the iliac wings are also concave like that and now iliarcus muscle lies in the belly of this concavity here so our iliac wings now head anteriorly towards the pubis so our pubis comes anteriorly towards the pubic symphysis and we have a superior pubic ramus and an inferior pubic ramus which heads out more posteriorly and inferiorly that inferior pubic ramus heads towards the ischium and our sitting bones here or the part where the bone would touch our seat as we sit is known as the ischial tuberosity our ischium then heads up towards our ilium posteriorly making up our ischial bone posteriorly here you can see our ischial spine also extending towards our sacrum on that side our acetabulum is the hollowed out portion created by all three parts of the pelvis and that creates the socket for our ball and socket joint of the hip now our acetabula actually face slightly anteriorly allowing our femur to come anterior allowing our legs to come out anterior to us and prevents those legs going back too far we can't sit with our legs crossed behind us or at least icons then we have our femoral head which articulates with that acetabulum ephemeral neck getting towards our proximal femur as well as our greater and lesser trochances which are important attachment sites for various muscles if we were to rotate this pelvis round we can look at an angle posteriorly we can see the iliac Wing here in iliac crest here we have the attachment side for our gluteus muscles and you can see anteriorly we have our anterior superior iliac spine and our anterior inferior iliac spine here posteriorly they're often forgotten about posterior superior iliac spine and posterior inferior iliac spine right at that s i joint as the iliac crest comes towards our sacrum here here we can see our posterior sacral foramina allowing for those nerve roots to exit the sacrum we can see our ischium or ischial bone much more clearly here posteriorly and see how it makes up that posterior wall of our acetabulum here's our ischial spine that we saw earlier pointing towards our sacrum and our ischial tuberosity here on the right hand side of the patient you can see the superior pubic ramus and the inferior pubic ramus of our pubic bone when we think about the acetabulum itself we can talk about this Rim here being the posterior acetabular rim and anteriorly we have our anterior acetabular rim and then that thin bone heading out towards our ischium here this is our posterior wall of the acetabulum we also have an anterior wall of the acetabulum so now that we've got a better 3D understanding of the pelvis let's have a look at our frontal radiograph and start by naming some of the Bony landmarks we can start in the proximal femur here we can see our lesser trochanter and our greater trickanter of the femur and the line between these two is our intertrochanteric line then our femoral neck heading up to the head of the femur which is sitting within this acetabulum this is our hip joint here the posterior rim of our acetabulum you can see here and it's a bit more difficult but you can see our anterior rim of the acetabulum here we know that those acetabular sockets lie facing slightly anterior that's why our anterior Rim is a bit more medial here often that anterior Rim goes in line with the superior pubic Rhema so that's another way to find that anterior rim and often the morphology between people is quite different so we can see the relationship between the posterior and anterior rims might change as the anterior version of that acetabulum changes we can then see our Superior pubic ramus and our inferior pubic ramus with our pubic symphysis here and this line is known as our pectinyl line across that Superior border of our Superior pubic ramus we can see our ischial tuberosity here and our ischium heading off posteriorly behind that acetabular joint here is our anterior superior iliac spine and anterior inferior iliac spine of the iliac wing and iliac crest going across the top there's our posterior superior iliac spine and maybe this is quite difficult to see as our posterior inferior iliac spine we can see our lumbar vertebrae here we can see our L5 lumbar vertebra with its transverse processes here our intervertebral disk space we can also see the vertebral spines heading out posteriorly there it's quite difficult because of all the gas within the bowel here to see the sacrum world but we can see how S I joined here our sacral iliac joint with our sacral ala here and further down we can see our coccyx bones coming down here and then lastly we're looking at the sacrum here we know that our ischial spines Point backwards towards our sacrum and actually if I head back to this image here we can see that this ischial spine is pointing towards our sacrum and there's actually a ligament that comes here we will look at later between our ischial spine and the sacrum as well as our ischial tuberosity in a sacrum which makes two separate foramina posteriorly here so we've had a look at how bony landmarks let's have a look at some pelvic lines now the pelvis itself creates a ring of bone and when we fracture that ring often as any ring created in the body one fracture in the ring often leads to another fracture in the ring and with pelvic radiographs often fractures are quite difficult to see or occult we can't see them at all and we can draw a couple of lines within the pelvis and if there's disruption of those lines we should really suspect a pelvic fraction if we identify one pelvic fracture we should then go looking for a second pelvic fracture so the first line is this main pelvic ring that I've shown you before and the first half of that main pelvic ring is known as our iliopectineal line I told you here's our pectin your line so we go from the ilium to alpectineal line is our iliopectineal line must be nice and smooth there we can then draw a line in theory ilio ischial line and this line up here must be nice and smooth as well our ilio issue line that ilio issue line comes on the medial surface of the ischium here and then heads up to the superior surface of that inferior pubic ramus we can also draw a line known as shenton's line where we follow the medial border of this proximal femur ignore this lesser tricanta we follow that up towards the neck of the femur curve immediately and that should go nice and smoothly with the inferior border of that Superior pubic ramus there other lines we can look at are these arcurate lines of the sacrum you see these lines heading out posteriorly here which helps us to identify any sacral fractures those accurate lines coming across like that we can then think of the pelvis as also having an anterior and a posterior column and it's a strong column of bone that we can draw all the way from the ilium down into firstly our anterior column which is our Superior pubic ramus up into the eyelid that's known as our anterior column of the pelvis we also have a posterior column from our ischium all the way up into our ilium that's our posterior column of the pelvis and again when going through a pelvic x-ray it's important to look at these lines and any disruption of those lines increases our index of Suspicion for a fracture now let's go about the difficult task of naming the various muscles that attach to these bony features that we've labeled now it's going to feel like a very long list of muscles that I'm going through and the reason I'm going through this is one to gain an appreciation for the relationship between the muscles and the bones of the pelvis but two and it's a fact that we can't get away from is that in exams often you're not asked to name the Bony feature but ask to name a muscle or a ligament that attaches to that feature so I'm going to go through the major ones here there are smaller muscles and ligaments that I'm not going to mention but by Far and Away these are the ones that you really do need to know when looking at a pelvic x-ray especially when you're in an anatomy exam so let's start by having a look at our psoas muscle that comes from the lower lumbar vertebra as well as our iliarcus muscle that sits in that concavity of the wing of the ilium here those two then come down and join together to form our iliopsoas muscle that heads towards our lesser trochanter of the femur here and you can actually see that little fat line of where that idiosoas muscle comes down and joins to that lesser to cancer we can then look at our anterior superior iliac spine which has our Sartorius muscle that heads all the way down to the tibia it actually bypasses the femur heads from the pelvis all the way down to the tibia our rectus femoris then attaches to this anterior inferior iliac spine heading down towards the femur there we can look at our greater trochanter now our greater turkanta has a lot of muscles coming posteriorly and attaching to that greater decanter or just below the greater trochanter and the way I go about learning these muscle attachments is by starting at the superior border of our pelvis and heading our way down and thinking of the various muscles that hit down posteriorly so let's start at the top here we have our gluteus Minimus and gluteus medius muscles that head from that posterior surface of these iliac wings and head down towards the greater trochanter itself inferior to that we get our piriformis muscle which heads from this lateral border of our sacrum posteriorly round towards our greater trochanter below the piriformis muscle we have our Superior and inferior glamela muscles that head out and attach just below the attachment of that piriformis muscle then we can think about this obturator foramen that's created by the superior pubic ramus and inferior pubic ramus and on the internal surface of that obturator foramen we have what's known as our obturator internus it's coming from the inside of the pelvis heading posteriorly behind the neck of the femur here behind the ischium here and heading towards our greater tricenter there we then have a muscle called the quadratus femoris that comes from the lateral border here of the ischium and also heads out just below the greater trochanter inserting on that side and lastly we can think of the muscle on the external surface of this obturator foramen known as our obturator externus which attaches just below the greater tricante in the tricenteric notch so all of those muscles are heading from the pelvis to the posterior aspect of this greater trochanter and the many muscles that attach to the anterior aspect of the greater trochanter which are more involved with the femur itself involved in extension of the knee and we're going to talk more about those muscles when we look specifically at the hip and the femur itself we can then look at muscles of abduction that cause the lower limb to abduct and we can think about those in a superficial and a deep layer in our superficial layer we have our pectin ears easy to remember comes from the pectinyl line heading towards the femur and just medial to the pectiners we have our adductor longus deep to the adductor longus we have our adductive brevis as well as our bacillus muscle and so those four muscles that are part of our adductor complex so those are the major pelvic muscles that I want to cover here we're not going into the internal pelvic muscles we'll look more closely at that when we look at an MRI of the pelvis and we're looking at the relationship of those muscles with the rectum and other organs within the pelvis itself so we've named them major muscles and the muscles of the pulvers are largely involved in movement movement of the hip joint as well as actually extending across that knee joint for some of those muscles but a major function of the pelvis is not only movement but it's also weight bearing or stability and the way this pulvis is designed is to allow us to take Central weights over our spine here and distribute it evenly to our legs and we need some way to distribute the weight being put through the sacrum here into now our lower limbs and the way we do that is with some clever geometry and let me just get my pen out here and we can draw some of that so we can see that our weight is coming here through the spine and wedging onto our sacrum here we can see our sacrum is taking most of the weight here now when we draw an arch we can get a shape like this if you think of an arch being built by five bricks here in this image we have the top of our Arch which is known as a keystone it allows for weight to then be distributed evenly on either side of the arch and that's exactly what the sacrum does it prevents our spine from falling through this way and distributes that weight out through the pelvis and into our lower limbs now in order for this distribution to happen without these bones falling away from one another we need quite strong ligaments to hold all of this in place so let's finish off by having a look at some of the major pelvic ligaments that provide stability within the pelvis the first ligament that we can look at is our ileolumbar ligaments that connect our ilium to our lower lumbar vertebra that allows for some stability of those iliac Wings to not be pushed away from our sacrum like that we then have sacroiliac ligaments both anterior and posterior sacroiliac ligaments that provide stability across these SI joints those ligaments run from a medial to lateral trajectory we then have ligaments that stabilize the hip joint itself we've got three major ligaments heading from the pelvis to the femur surrounding the neck of this femur those ligaments are the iliofemoral ligaments are pubofemoral ligament and our ischiofemoral ligament and the way those ligaments wrap around the neck of the femur there they go around it in a spiral pattern what that spiral does it allows us to flex our hip allows our leg to come out anteriorly and as our hip flexes that spiral loosens it unwinds allowing for more movement of that femur anteriorly but as we head our FEMA posteriorly extend our hip the spiral tightens and prevents anterior dislocation of that femoral head from our acetabulum now as we mentioned those acetabuli lie facing forward so we don't want that hip to pop out anteriorly and it's a spiral ligaments the iliophemoral pubofemoral and ischiofemoral ligaments that prevent that hip from popping out anteriorly from that acetabulum we then have a ligament that heads from our anterior superior iliac spine to our pubic bone here and this is what's known as our inguinal ligament our inguinal ligament heading across here and as you may recall our inguinal ligament makes up the floor of our inguinal canal and then lastly we mentioned a ligament heading from our sacrum towards our ischium that creates two foramina posteriorly within the pelvis itself that's what's known as our sacral spinous ligament coming from the sacrum to our ischial spine here as well as our sacral tuberous ligament from our sacrum to our ischial tuberosity there posteriorly it goes behind the superior pubic ramus and this creates a foramen here this is our greater sciatic foramen and our lesser sciatic foramen so posteriorly we've got our greater sciatic foramen as well as our lesser sciatic foramen anteriorly we have these obturator foramina here now actually not much passes through these obturator parameters It's actually an osseous membrane or ligamentous membrane in between our Superior and inferior pubic Rami and we have that obturator externus and obturator internist muscle overlying that octurator foramen so we've covered a lot the pelvis at first glance looks quite simple but there's so many bony features and muscles interlocking between one another and ligaments heading in all different directions and the best way to learn this is to start by labeling the Bony features become confident in identifying the various different bony features and then think about muscle movement and where the muscles need to attach in order to create the movement that that muscle functions to do but knowing where these muscles attach can be really important and the most common example of this before we end off is our iliopsoas muscle that attaches to this lesser tricante here often this trochanter can be avosed off of the bone here when tension has been put through our iliopsoas muscle and causes a break of this bony prominence here and that can happen on our anterior superior iliac spine are greater to counter a whole bunch of areas and knowing these attachments helps you to identify where those different fractures can occur so it's been a lot go through the lecture multiple times if you need to become more and more familiar with the anatomy this is going to need to be second nature before we then head into a pelvic or hip MRI and try and identify even smaller more detailed anatomy And if you like this way of learning by looking at a radiograph and then layering on the various different pieces of anatomy cementing the anatomy in your mind consider subscribing to this channel liking the video letting me know that you like it and speaking to me in the comments and until next time I'll see you all goodbye