Hi, everyone. Welcome to our AAPMNR 2021 session titled Musculoskeletal Radiology Fundamentals. And today we will be going over the HIP with some fantastic speakers. My name is Jennifer Suhu and I'm one of the sports medicine attendings at Weill Cornell Medicine and New York Presbyterian and I'll be the moderator for today's session. Before we delve into our session, some housekeeping items to go over. So in order to make sure we have enough time for all of our speakers, we'll be saving most questions until the end of the presentation. Please use the chat function below to ask questions. You can send the question either directly to me or to the entire group. I have no relevant financial disclosures. And then this is just a quick outline, outlining what we'll be talking about today. So first up will be Dr. Catherine Bartolo, who is an assistant professor and one of the sports medicine societists at UNC's PMNR program, who will be going over pediatric HIP x-ray. Then we'll have Dr. Nathan Oleson, who is an assistant professor and one of the sports medicine physiatrists at Washington University's PMNR program, who will be going over adult HIP x-ray. And then we're lucky to have Dr. Ashish Patel, who is an assistant professor of clinical radiology and radiological studies and one of the MSK radiologists at Vanderbilt, who will be going over MRI of the HIP. Then we'll spend any last several minutes answering any questions you may have. All right, Dr. Bartolo, why don't you kick us off here? I'm going to stop sharing my screen. All right. So to get started today, we'll be focusing on the fundamentals of pediatric HIP x-rays. I have no relevant disclosures. So our goal for the first part of this session is to review what normal anatomy looks like on a pediatric HIP and pelvis x-ray. Then we'll be reviewing commonly ordered x-ray views to evaluate for the pediatric HIP. And finally, we'll be going over x-ray findings of common pediatric HIP and pelvis pathology. There's a lot of overlap, hence the HIP and pelvis. So first things first, the big difference when looking at pediatric HIP and pelvic x-rays compared to adults is the presence of birthplates. So two main types of birthplates, you've got your physis or the epiphyseal plate. These are located at the ends of long bones and are usually associated with an articulation. Then you've got your apophysis, which is located more at bony prominences, and they tend to be associated with ligamentous attachments or tendinous attachments. Usually you keep in mind the muscular attachments at this location. So the main physis to be aware of when you're looking at the HIP and the pelvis is the proximal femoral physis. And denoted here by the blue arrow. And it's this line right here. And then the E here is denoting to you that this is the location of the epiphysis, which become relevant when we discuss different types of pathology later in the talk. The proximal femoral ossification center appears in the first year of life and then closure occurs in the mid to late teen years and occurs later in males than females. Then there are many apophyses about the pelvis and the HIP. As you can see here, denoted by the arrows. So we've got one here at the iliac crest, another at the anterior superior iliac spine or the ASIS. Another one is located at the anterior inferior iliac spine or the AIIS, the greater trochanter, the lesser trochanter located here, the pubic symphysis, and the atrial tuberosity. I just want you to note here what these look like. It's really important because it can be easy to look at a pelvic or hip x-ray of a kid if you're not used to it and think these look like fractures, but this is normal pathology to see these lines here where you see the apophysis and when you see the epiphysis, I mean, the physis here. Okay. So as I mentioned, there's apophysial attachments. And so it's important to remember your anatomy and what attaches where. This can be relevant when you're considering injury mechanism or diagnosis. And so I've highlighted specific sites where they're most common locations of avulsion fractures. And so our most common ones are going to be at the ASIS, the AIIS, and the atrial tuberosity here. I'll let you review these on your own time, but they're good to commit to memory. So a quick note, a bit more about the iliac apophysis. So the ossification of the iliac apophysis can serve as an indirect measure of skeletal maturity, and this can have relevance when thinking about management and treatment of scoliosis. So the amount that the iliac apophysis is ossified is thought to tell us about how much growth is expected in the future for a kid and then can inform, do we expect there to be curved progression in a kid who has scoliosis? So there's two accepted systems. The one I've presented here is called the original system and is the one that's predominantly used in the United States. There are a total of six grades and the first grade is zero. So RISR grade zero is considered, the iliac apophysis is absent. So you can see here on the right side of the screen, denoted by the yellow arrow, that there's a very thin black line. And this is between the iliac apophysis and then the iliac crest. And so that won't be there. You won't see it at all. And that means that it's grade zero. Then the iliac crest is divided in four different quadrants. And as the ossification, which basically just means as it starts to grow, it starts to exist and be present. It will go through all four of those quadrants. And as it does, then it will move through grades one through four. Grade five means that the ossification is complete and now it will start to fuse with the iliac crest. This is relevant because when kids are more in RISR zero and one, they're further away from skeletal maturity. And so we can assume that they're likely to have high potential for significant growth in the future, as opposed to kids who are in RISR grade four and five. They're likely nearing skeletal maturity and have a lower likelihood for significant potential growth in the future. This can help inform us once again about scoliosis. You know, do we expect it to get significantly worse in the future or it will likely, is unlikely to progress. So commonly ordered views when we're considering the pediatric hip and pelvis are going to be your anterior posterior or AP view and the frog leg lateral view. It's important to consider ordering bilateral studies for comparison. This can sometimes be very helpful when trying to identify pathology in the affected hip when comparing it to the contralateral unaffected hip. So for the anterior posterior view or AP view, the patient is supine. The leg is internally rotated slightly about 15 degrees. We want to pay attention to avoid pelvic rotation. We don't want asymmetry because of pelvic rotation. This will allow us to better evaluate for pathology. The detector will be located posteriorly so that the extreme beams are passing anteriorly to posteriorly. This view is best for visualizing dislocation, developmental dysplasia of the hip, apophyseal avulsion fractures, and leg calvae Perthes disease. So just take a look again at the location of the apophyses and the proximal femoral fissus here to commit those to memory so that you don't accidentally call those a fracture when it's just normal anatomy. The second view that's commonly ordered is the frog leg lateral. For this position, the patient is again supine and we're paying close attention to avoid pelvic rotation. In this case, the knee is flexed to about 30 to 40 degrees and the hip is also flexed to about 40, 45 degrees as well as abducted and externally rotated. Sometimes the sides of the knees are propped up with sponges or bolsters to help for discomfort. This is best for visualizing, this is best for visualizing slipped capital femoral epiphysis or SCIFI and can also be helpful in evaluating leg calvae Perthes disease. It's important to note that you do not want to order this view if you suspect that your patient has a hip dislocation or a fracture as the positioning required for this view can worsen that pathology. So the first pathological condition we will be considering is slipped capital femoral epiphysis or SCIFI. This involves translation of the proximal femoral epiphysis and is considered a type 1 Salter-Harris physiofracture. Classical presentation for this condition is in a child who's about 10 to 15 years old, more common in males and is sometimes associated with obesity although there is a small class of patients that are not obese and still present with this condition. They generally complain of hip, groin, thigh or even knee pain, have a limp and don't usually report a history of trauma. In this case it's really important to consider getting bilateral views. It is very common, some studies describing about 50 percent of children who present with bilateral disease, you don't want to miss that by getting only a unilateral view. The frog leg lateral is really important when considering this diagnosis and I've presented two views here for you to compare this. The reason why the frog leg lateral view is so important is because translation of the proximal femoral epiphysis often is initially in the posterior direction and may not be readily viewable on the AP view and could be missed and this is especially true in mild or early stages of the disease. And so you can see here on the AP view in this particular example there does appear to be, you know, some slippage that you can appreciate to the naked eye here down in the inferior aspect but when we look on the frog leg lateral view it's much more obvious and you're not going to miss that. Over here you can see that that proximal femoral epiphysis has slipped significantly. This is a much higher grade of the disease and this would be much easier to pick up even on the AP view as I've presented here. So not getting too into the nitty-gritty here as we're focusing on the fundamentals but it's important to know that there are grading systems that you can use to determine the severity as well as the prognosis for this condition. And so there are two different grading systems. One's looking at the degree of slippage of the epiphysis relative to the metaphysis and the other one is looking at the angle of slippage. And it can be pre-slip, mild, moderate, or severe. A radiographic measurement to be aware of though that is helpful is called Klein's line. So you can do this by creating a line along the superior aspect of the femoral neck and a normal hip as you can see here on the right. Klein's line should run and intersect a decent part of the lateral proximal femoral epiphysis. In this case it's about the lateral quarter but in a hip that has slipped capital femoral epiphysis it's not going to transect as much or it's going to miss it entirely. So when you're measuring this you want to look and see is it completely you know missing the lateral aspect entirely or you can say oh well it's it's transecting it somewhat but not nearly as much as it is on the contralateral side. If there is an abnormality when performing the measurement of Klein's line this is referred to as Trethewey's sign. And can be really helpful in milder forms of this disease because sometimes you can miss it because you're looking at for example this one this AP view here and it doesn't really look like there's much slippage to the naked eye but when we use Klein's line it's apparent that there is some slippage compared to this side. The second pathological condition that we will be covering is Legg-Calvé-Perthes disease commonly referred to in short as Perthes disease. This is idiopathic avascular necrosis of the proximal femoral epiphysis. There's varying stages of this and it common presents in children who are about four to nine years old. It's once again common in males and presents with vague hip pain also a limp and on physical exam they tend to have decreased internal rotation. For this one you'll obtain your AP and your frog leg lateral view and then you're looking to see that there's degeneration essentially of the proximal femoral epiphysis. You can see on this side is normal it's there and robust and on this side we can see that it's fragmenting and disintegrating and there's really not much left here on both views. Additionally, we start to see that there's flattening and widening of the femoral head which is more apparent on this next slide. A couple of the hallmarks that you can see on x-ray is this crescent sign here which is more common with the second stage and fragmentation and then once again here that flattening and widening of the femoral head which is usually much more apparent in later stages of the disease. And finally, we're going to review apophysial avulsion fractures. So we touched on all of the many apophyses about the hip and the proximal femur and the pelvis earlier in the talk and their muscular attachments. And so when you're concerned for an apophysial avulsion fracture, you'll usually just get an AP view. This will usually be sufficient to locate and identify your pathology. And so here I've demonstrated an ASIS avulsion fracture but sometimes with subtle or minimally displaced avulsion fractures at the ASIS, AIIS, or iliac crest, the fracture may not be as apparent on your AP view. If you continue to have very high clinical suspicion, you can consider ordering a Judae view which is a 45 degree oblique view of the pelvis. This view usually is used for evaluation of acetabular and pelvic rim fractures but once again can be helpful if you have a high degree of clinical suspicion or an avulsion fracture at these three locations that I mentioned and it's not showing up on your AP view. As you can see, it's a bit tough to make out but it's a much more prominent on this one that you can see it coming off as opposed to on the AP view here on the Judae. And finally, just to wrap things up, a couple more examples of common apophysial avulsion fracture locations. On the left, we've got the ischial tuberosity avulsion fracture. You can see that there is this osseous deformity as compared to the other side coming off of the ischial tuberosity and lastly at the AIIS, we can see that there is this osseous irregularity coming off of the AIIS which is an avulsion fracture. So thank you so much for your attention and I'll hand it off now back to Dr. Suhu. Thank you, Dr. Bartolo. That was fantastic. Next up, we have Dr. Olison who will be going over the adult x-ray. Hi everybody, I'm going to share my screen. Okay, so we're going to get started on the fundamentals of adult hip radiographs. I have no financial disclosures or conflicts of interest. What we're going to try to cover today is the typical hip radiograph series. We're going to talk about how to assess for image quality, also how to do a systematic assessment of these x-rays and loop in some pathology. For indications, as Dr. Bartolo mentioned, typically we're ordering these x-rays for pain. It's important to note, however, that intra-articular pain does not only manifest in the groin but can manifest elsewhere as well. Impaired motion and gait or other abnormalities that could be present and suspected referred pain such as pain in the knee. It's important to note that the radiographs we're going to discuss today will not be appropriate for the trauma setting. The typical views include the AP pelvis, as mentioned previously, as well as some hip abduction and flexion views including the DUN and the previously mentioned frog leg lateral view and lateral views including the cross table lateral and the false profile. We're going to focus our attention today mostly on the AP pelvis, DUN and false profile. When considering which views to order, it's really important to consider what aspect of the femoral acetabular joint is best imaged. When assessing the acetabulum, the AP pelvis and the false profile view are really important. All of the views can assess the proximal femoral head neck junction, but the DUN view especially, as well as the other views listed, are good for assessing this area. We're going to focus on these ones highlighted here in blue. Now we're going to move on to the AP pelvis, which is pictured here on the right. This can be obtained in supine or weight bearing. Weight bearing especially is important for assessing for joint space narrowing. As previously mentioned, the limb is internally rotated and then the beam is centered between the ASIS bilaterally and the superior aspect of the pubic synthesis. To assess for appropriate image quality, we need to talk about neutral pelvis rotation and optimal pelvic tilt. Here we have an AP of the pelvis and the limb is internally rotated to compensate for the typical femoral anaversion that is present. This lengthens the femoral neck and allows us to be able to visualize the femoral head neck junction here. Also, if the limb is externally rotated, the greater trochanter may cover up the head neck junction and the acetabulum. For neutral pelvis rotation, this is defined by the alignment of the coccyx relative to the superior portion of the pubic synthesis, as pictured on the right. The obturator foramen, which are starred, should be symmetric. The radiographic teardrops, which are indicated by the arrow, should also be symmetric and the iliac wings should be as well. This is vital when you're assessing joint morphology, especially acetabular morphology, which is heavily influenced by rotation. Similarly, acceptable pelvic tilt is defined here on the right by the distance between the sacrococcygeal joint and the superior pubic synthesis. Sometimes it's hard to assess for the location of this joint, so you can measure the tip of the coccyx to the superior pubic synthesis. There are distances that are reported for the acceptable distance, as indicated here on the left. Again, this is important because of joint morphology, especially things like acetabular version are heavily influenced by pelvic tilt. The AP pelvis is really useful for osteoarthritis assessment, as well as previously mentioned pubic synthesis pathology, but what we're going to focus on today especially is acetabular morphology, femoral head neck junction abnormalities, both of which can be seen in FAI or hip dysplasia. And finally, tendon origin and insertion pathology, as indicated by our figure here and in the previous talk. Later on, we're going to talk about pathology for the topics highlighted in blue. Here is the DUN view, which is one of the views that we often use in adult, especially young adult hip assessments. The patient is supine, and again, the pelvis and the leg are neutral, but the hip is abducted, and the hip can be flexed either 45 degrees, as indicated in this picture here, or 90 degrees, which is indicated in this picture here. When assessing image quality, there are some similarities with the AP pelvis, where the iliac wings need to be symmetric, the obturator foramen, which are starred, should be open, and then the greater and lesser trochanters, which are indicated by the arrows, should be in profile. In this 90-degree DUN view, there's a lot of tissue overlap over the joint, which can make it hard to see, whereas here, in the 45-degree DUN view, there's less tissue overlap. The DUN view is really helpful at looking at the femoral head-neck junction, as indicated by the arrow, and likely is the best view for assessing that superior or anterior lateral aspect of the head-neck junction, typically where the cam deformity is present. Of note, this view should not be obtained for a hip fracture, as previously mentioned, because it requires motion. Finally, we're going to talk about the false profile view. This is obtained while the patient is standing, and the hip to be imaged is against the cassette, and the foot is parallel, and then the hip is rotated away from the ipsilateral hip, and the beam is centered at that hip. It creates an image like this. To assess for image quality, we really need to make sure that the ipsilateral hip can be clearly seen and is not overlapped by the contralateral hip. This is really useful for looking at the anterior acetabular coverage and for the anterior inferior iliac spine. These here can cause a type of extra-articular impingement called sub-spine impingement. Now moving on to our pathology and assessment checklist, the first thing to do, we already did, which is to assess image quality. Then for the AP pelvis, DUN, and false profile views, there are abundance of things that could be assessed for. When you assess your x-rays, you should go through all of these, but in the interest of time, we're going to be focusing on these highlighted here in blue. degenerative changes, and head-neck junction abnormalities. Specifically in the AP pelvis, what I've listed here in this sort of lengthy slide are all of the different pathology that can be seen on the AP pelvis and their specific things that they relate to, such as depth of the acetabulum, for example. We're going to be focusing on coverage and then joint space abnormalities and degenerative change. A few definitions that are important to assess for or to define prior to moving forward is what hip dysplasia means. This is really a disorder of acetabular coverage and acetabular development. This differs from femoral acetabular impingement, where there is pain from mechanical impingement of the hip during hip motion that results from abnormal hip morphology. Typically CAM and pincer are the types that are described, with CAM being an abnormality of the head-neck junction and pincer being an abnormality of the acetabular overcoverage. So to assess for this, there are a number of different measurements and angles, and we're going to focus on a few of those. First we're going to talk about the lateral center edge angle, which is pictured here on the right. The AP pelvis is the view to obtain this, and it really assesses for the superior lateral acetabular coverage. To make this measurement, there's three lines that are important to describe, this transverse pelvis axis line, and then this vertical perpendicular to the transverse pelvic axis line that stops at the femoral center. The final line goes from that femoral head center to the lateral sorcel, or where the sclerotic weight-bearing portion of the acetabulum is. This angle is the lateral center edge angle. When reduced, it's consistent with hip dysplasia. When increased, it's consistent with pincer-type morphology. To drive this point home, this picture here has a normal lateral center edge angle, whereas the picture here on the right has a reduced, and this is consistent with hip dysplasia. Similarly, in the anterior center edge angle, we're going to define acetabular coverage, but in a different view. This is the false profile view, and we're defining the anterior aspect of the acetabular coverage. Similarly, there's a transverse axis line, as well as a vertical line through the femoral center. Then the final line, as indicated by number one and then number two, goes from that femoral head center to the anterior portion of the sorcel, or the sclerotic weight-bearing portion of the acetabulum. The angle created is your anterior center edge angle, and normally is 20 to 25 degrees or greater. That's indicated by this picture here. On the picture on the right, there's deficient acetabular coverage, which is consistent with hip dysplasia. Also, this view can look at, as pictured here, abnormalities of the anterior inferior iliac spine, which can cause extra-articular impingement, also called subspine impingement. Now we're going to move on to CAM deformity assessment. In the head-neck offset ratio, what we're trying to do is quantify how much of an offset is present from the head to the neck. This can be obtained on a number of different views, and it's really useful for CAM deformity assessment. Three lines are described first, and then a final line that we'll go through. Number one is through the femoral neck center to the femoral head, and the two lines are parallel to that, indicated by number two at the anterior femoral neck, and indicated at number three in the anterior femoral head. The difference between line two and line three is the head-neck offset, and then the ratio is when you divide that by the diameter of the femoral head. A reduced femoral head-neck ratio is consistent with a CAM deformity. This picture here is very normal, where you can see there's no CAM deformity. These pictures here, especially the picture on the right on this 45-degree DUN view, you can see a very obvious CAM deformity and a reduced head-neck offset ratio. The final measurement we're going to talk about is the alpha angle, which is pictured here. It's again obtained on multiple different views, especially the DUN view, and it's to assess for CAM deformity. It starts with a femoral head best-fit circle, as indicated by number one, and again that number two line goes from the femoral neck to the femoral head center. Finally, the third line, which is somewhat hard to understand, goes from the femoral center to where the neck extends outside that best-fit circle, or where the head loses its sphericity. There's controversy about what is normal, but generally accepted as greater than 50 to 60 degrees is an increased alpha angle. You can see here a clear CAM deformity with an increased alpha angle. Similarly, on these two pictures, obvious CAM deformities with increased alpha angle. Now moving on to osteoarthritis, which will be our final area of focus, there's multiple classification systems that exist, including the TANUS, Keldrin-Lawrence, and CROTH. In assessing for these, it's important to really understand each of these grading systems. Comparing the inter-rater reliability and sensitivity and specificity is really outside the focus of this talk. We're going to focus on this here. We're going to focus on this hip here, where you can see some joint space narrowing without any substantial sclerosis or cysts. This is consistent with a TANUS grade one. For the CROTH and Keldrin-Lawrence, minimal joint space narrowing or possible joint space narrowing is a CROTH two or Keldrin-Lawrence one. We're going to drive this point home with a more severely arthritic hip here, where you can see very large cysts, osteophytes, deformity of the femoral head, and obliteration of the joint space. That's a TANUS grade three, as well as a CROTH grade five and Keldrin-Lawrence grade four. Thanks for your attention. Here are my resources, and I will be turning it back over to Dr. Suhu to introduce our next speaker. Great. Thank you, Dr. Olison. That was fantastic. All right. Next up we have here is Dr. Patel, who will be going over hip MRI. Good afternoon, everyone. I'm Dr. Patel, Ashish Patel from Vanderbilt University Medical Center. Wanted to thank you guys for having me to talk about the MRI aspect of hip pathology. I don't think I need you to, I don't think I need you to, I think it's pretty obvious that an MRI is an incredibly big topic. We may not get to all of the topics, the relevant topics in this one presentation, but I hope to get to some of the bigger points that I think would be important for you guys as a practice. Disclosures. I have no, no disclosures. I want to take a quick second and thank all the veterans, men and women in uniform, past, present, and future. We appreciate your service. So I think Dr. Patel and Dr. Olison did a phenomenal job really kind of breaking down just some basics of what do you need to look for in an X-ray, and an X-ray, like I tell my residents, I tell my fellows, I tell ordering clinicians, it's a must. You know, there are a lot of things that MRI can solve, but there are a lot of simple things that they can't, it can't pick up. And that's where a nice X-ray can kind of really, you know, fill in the gap and really look for more subtle type of findings. For example, an X-ray is going to be phenomenal in looking for soft tissue calcification or subtle cortical regularities that would be missed on MRI. So what I can convey is please don't underestimate the power of a good X-ray. They can really kind of work towards and help towards a strong diagnosis. Hip pain, I don't think I need to really talk about this too in depth, but anything that can cause, you know, affecting the joints, soft tissues, it's, you know, it can be referred from groin pain, you know, undiagnosed hip pain, undiagnosed osteoarthritis can lead to really kind of accelerated deterrent of osteoarthritic changes. And X-rays, like I said, serve a really important role in assessment of FAI or arthritis, ambony evulsions, and again, can be underestimated. And sometimes X-rays are really, really helpful to really make sure that there's nothing major going on and kind of exclude major pathology from the get-go. We hear the normal X-ray of a pelvis, you know, we see normal hip articulation, normal pubic symphysis, normal SI joint. And so sometimes it's nice to be able to see a normal, and sometimes the findings on these studies are really, really, they're very obvious, right? So we can often tell on an X-ray, like that there's some, you know, really gnarly pathology going on in terms of avascular necrosis, subchondra collapsed, but sometimes these findings are not really obvious, right, they're more subtle. So for example, take a look at this X-ray where we can see subtle areas of geographic bony sclerosis, serpentine geographic bony sclerosis, really kind of conveying the pathology of AVM. X-ray, as perfect as it is, it can be helpful when it's obvious, when it's subtle, it can be more difficult, you know, again, it's just one tool in an armament of tools. CT, you know, excellent looking for subtle fractures, subtle pathology, you know, there's some things that can't be found on X-ray or you're questioning, like we see this hip, so radiographed frontal of the left hip, shows a little cortical regularity involved in the left femoral neck, while on CT, these findings are very, very obvious, right? So again, X-rays, get them, they can give you a lot of information, but if we're ever in doubt, always bump up to the cross-sectional study. Ultrasound, another great modality to use, you know, I myself trained heavily in musculoskeletal ultrasound when I was a fellow. It's great, but unfortunately it's highly user dependent, it can, you know, depending on the patient's body habits, you can have inherent limitations. Great for assessing for hyperemia, so there's some pros and cons with every imaging modality. So let's talk about MRI really quickly here, excellent, excellent for fractures, bony tendon avulsion, inflammatory arthropathy, osteonecrosis, you know, really what I tell my residents and fellows is that, you know, when you're ever in a situation where you need to really assess the soft tissue, assess for a septic joint, assess for inflammation, MRI can be a great tool, right? It'll allow you to look for bone marrow edema, it can allow you to look for abscesses that may not be as readily seen on CT, may not be as readily seen on ultrasound if the patient's large enough. And so MRI is a great, great tool. Other benefit, you have multiple imaging modalities, right? You have multiple imaging sequences, you have a T1, great for assessing fat, STIR, wonderful assessing, you know, edema. Just here real quick, I wanted to really touch base on this really quickly. So according to the American College of Radiology, we have recommendations where MRI is appropriate, where MRI may not be as appropriate, and it's really gonna extend through all imaging modalities that we have to work with, X-ray, ultrasound, even CT. And so there for a few different types of pathology, for example, for chronic hip pain, MRI is rated a nine, and nine is usually appropriate, highly recommended, you know, four, five, and six may be kind of a moderate, may be appropriate potentially, and one, two, and three is not appropriate. For example, if someone's coming with hip pain for the first time, getting an MRI right off the get-go may not be appropriate. But this just kind of really emphasized the point that MRI is a vital tool in a radiologist armament. So some basics, every time we go through an MRI sequence today, I'm gonna try to break down in terms of whether it's a T1, whether it's a T2-STIR, whether it's proton density. And the reason for that is that each one of these sequences serve a different purpose. Each one of these serve a different role in making a diagnosis. A T1 is simply, what I want you to remember is a T1 is great for evaluating anatomy. Basically looking at bone marrow, looking at for muscle atrophy, it shows you great, great anatomic detail, sharp cortical, sharp margins between tissue planes, excellent for evaluating marrow fat. For example, if there's a patient that you're concerned that has some sort of underlying myelomatous process, looking for the loss of fat can really make a big, you know, really influence outcomes, you know, medical treatment. Key things to remember is that fat is bright, fluid is dark. Blood products are intermediate, and those evolve over time, depending on the timeframe between initial bleeding and subsequent laying. Again, key here, cartilage is intermediate in signal, labrum is intermediate in signal. So hyper-intense bright, you see that cortical line along the iliac bone, that's what I would consider hypo-intense dark, right? This is a coronal view, coronal T1 of the pelvis, again, showing you great anatomic detail. Again, marrow fat will be bright, fluid will be dark, labrum, you can probably see some of the cartilage right here, it looks more intermediate in signal. We have a T2 stir where you can have great evaluation for bone marrow edema. For an example of if there's concern for fracture, you'll see often, you know, a jagged line of hyper-intense signal, we'll see examples of that down the road. And again, fluid will be bright on a T2 stir, fat will be dark. So if you remember back in the previous case of the subcutaneous soft tissue and some of the gluteal fat looked incredibly bright, and the same example looks a little bit dark, right? And it's excellent to really evaluate for any type of edema. Again, blood products are going to be intermediate, cartilage will be intermediate, labrum will be dark. Proton density, so a lot of practices incorporate proton density. So you may look at this and say, well, hey, it looks like a T1, and it shares a lot of similar characteristics. And so without going into the nitty gritty detail, what I want you to really remember when you look at a proton density, if you have a concern for a case, is to really look for differentiation between hyaline and fibrocartilage. That's a really big tool that proton density gives us, is to really be able to differentiate between the two. Hyaline cartilage is the native cartilage that we have in our joints. Fibrocartilage is something that we can get. For example, if a surgeon does microfracturing in a patient that has, let's say, an osteochondral or chondral defect in a knee, a surgeon will often go in with a sharp tool, poke holes into part of that knee, and allow some fibrocartilage or scar tissue to develop. It's a really great way to assess for any type of potential pathology. Proton density fat set, so it shares a lot of similar characteristics from the T2 stirrup. And again, you're really looking for bone marrow edema-like signal. Fluid will be bright, really great for looking for effusions, muscle strains. So if you're looking for potential fluid within bone, potential fluid within muscle strains, your fat set proton density or a T2 fat set slash stirrup are going to be really great important modalities for you. This is a nice table that I got from Fundamentals of MSK Imaging book. And I think if you're really going to hone in on any slide of trying to get understanding of what pathology will look like in different sequences, this may be a good tool. So we've talked about some of this. Muscle will be intermediate, fluid will be low on a T1, remember, T1s are great for fat, great for anatomy, T2 will be great for looking for fluid and strain, and so on and so forth. Or again, like I said, you know, acute hemorrhage, chronic hemorrhage can really vary over time. So again, combining these two can really help you figure out how long a process has been going for. So to break it down into search pattern, right, I tell my residents and fellows this all the time, humans will make mistakes, technologists will make mistakes, ordering clinicians will make mistakes. It's a natural part of the process, right? It's a natural process of getting better every single day. But a good search pattern, taking your time, a systematic approach, a good search pattern never makes mistakes. Or if they do, they make less mistakes than if had you just gone in randomly. And so for every pathology, every joint, every study, I have a search pattern, and I try to really push to my fellows and residents to have a search pattern. So that way, when you're confounded with a really difficult case, you're able to really break it down into simplicity, because if you don't, it can be really, really confusing, really, really chaotic. In case you haven't noticed, there are going to be a lot of speed game references. I think in the middle of doing this presentation, my wife and I binged the entire show within two days, so be prepared. So here's how I break things down, right? So we have nerve osteostructures, so we'll talk about those in a tiny bit. I look at pubic symphysis, I look for pathology like osteoarthritis, we'll get into potential fractures of pubic symphysis and athletic prebalgia, look for SI joint pathology, right? In case of, you know, inflammation, I look at the gluteal tendon, hamstring tendon, so tendon insertions upon the pelvis, which is a common area for pathology. I look at the joints themselves, fractures, dislocations, and then I keep a nice little separate box for other stuff, right? Because no matter what you're looking for, there's always going to be something that you're not prepared for, and that's something that I want, really, really want to convey to everybody here. Okay, let's begin. So I'm going to break it down in terms of cases, and then we can kind of talk about it afterwards. So we'll show you a case, we'll show you the imaging findings, we'll talk, explain it, and then we'll look at a, like a comparison between normal and abnormal. So you have a single frontal radiograph of the pelvis. So just to kind of get everyone oriented, we have L3, 4, 5, S1, we have the iliac bones, right, left, pubic symphysis, superior and inferior pubic rami. We have the greater troch, lesser troch, and we see a normal looking radiograph, right? The joint spaces are preserved. I don't see fractures. This is Ward's triangle, by the way. If you're ever looking for fractures in an x-ray of the pelvis, look at Ward's triangle. It's basically a paucity or a lack of trabeculation overlap, and they're highly vulnerable areas for fractures. We see them often in trauma. Here we have, what? This is a T1 sequence. How do I know it's T1? Because I see fat looking really, really bright, the marrow looking really, really bright, and I'm looking at the muscles, which are intermediate, intermediate. However, if I look here, what do we see? We see hyper-intense signal that matches, what, fat, along the rights, piriformis musculature. We have a comparison on the left. So that's something to be aware of. We have, what? We have a coronal T1. We have the axial STIR, so get everyone oriented. Right, left, top of the head, feet. We see here is that we see the left piriformis musculature, nice, robust, and thick. However, when we look at the right side, we see this really kind of generalized increase T1 signal. On this axial fluid-sensitive, meaning STIR or T2 FATSAB, we see a really thickened, nice appearance of the left piriformis musculature, and kind of a, what, smaller, you would say, a little bit increased signal within the right piriformis musculature. I don't even make the argument that there's increased T2 signal, right? T2 fluid bright. This is what? These are examples of piriformis syndrome, rare condition due to entrapment of potentially the sciatic nerve, or even just abnormal trauma to the piriformis muscle itself. You can break it down into primary or secondary. Primary is more due to anatomic variation. Even though I showed you kind of a diminutive appearance of the piriformis, oftentimes you can have a really thickened appearance. Secondary is obviously due to kind of an extrinsic pathology like an enlarged lymph node, large focal fluid collection, osteophyte spur formation. What I tell my residents is that the S2 nerve root should basically surf on top of the piriformis, right? If the S2 nerve root surfs on top of the piriformis, not a big deal. If the S2 nerve root dips into the piriformis muscle and comes out, again, not a big deal. You may even have signal changes often, sometimes in the sciatic nerve or the S2 nerve root as it goes through the piriformis, again, not a big deal. We generally hesitate in calling any type of pathology unless there's a clinical context within it, but we'll often see variations in the S2 nerve root as it goes through the piriformis musculature. That's another great way to really kind of get anatomic bearings on where you're at is to look for the piriformis and look for the S2 nerve root, which should generally surf on top of it. So glide on top of it. Just to kind of a quick example of the sciatic nerve from L4 to S3. So it's got multiple components. This is the nerve root that I tend to look at when I really look at the piriformis musculature. Things to look for in potential piriformis syndrome, increased fatty atrophy, intramuscular edema, space-occupying mass within the greater sciatic notch, increased edema, which we saw with the piriformis. You can often see within the sciatic nerve. And then once in a while, you'll see kind of a, for whatever reason, hypertrophied piriformis muscle, which can sometimes be an issue if the S2 nerve root's going through it and there's symptoms associated with it. You have a coronal T1, right, left, head, feet, sacrum, sacrum, SI joint. We have the hamstring muscles or tendons here, and they're the piriformis. You can see how they're nice and symmetric. Intermediate signal, thickened, right? Now look at our abnormal example, right? Coronal T1s, again, coronal T1, great for anatomy, great for marrow fat. You see how there's this really kind of focal atrophy of that muscle compared to this, and then compared to how a nice normal symmetric looks like. Right? We have a normal T1, abnormal T1. And again, I'm really trying to emphasize the point of how that piriformis musculature on their own looks symmetric. Meanwhile, here it's focally atrophic for a number of reasons. Here, they're showing you an atypical lipomatous lesion. What is an atypical lipomatous lesion? Basically, a fat-containing lesion that's greater than five centimeters or has internal septations, abnormal thickening, neural nodularity. It looks nasty, right? You shouldn't have focal fat burrowing through the sciatic notch right there, as opposed to kind of a more normal setting right here. All right, case two, 70-year-old female with bilateral hip pain. I know this is an MRI lecture, so forgive me, but I did want to show some CTs here. So we have a chronal CT, we have an axial CT. So what we see here, right again, right, left, head, feet, axial, right, left, anterior, posterior. We see a little bit increased sclerosis along the left hemisacrum. And an MRI done subsequently shows on this T1, again, T1's great for anatomy, great for fat, great for marrow fat, a loss of normal marrow fat signals. So you look how bright this fat is, you see how dark it is. And then you correspond it with the T2 or STIR, great for fluid, great for fractures, where we see increased bone marrow demyelic signal along the anterior sacrum. And we see this kind of jagged irregularity along the sacroiola on the left and to a lesser degree on the right, which if you can even look here, you'll see it, it's often better manifested on the T1, which we'll talk about later on. Coronal views, T1, we have a STIR, fluid-sensitive coronal view, and again, showing the same type of pathology, jagged linear signal involving a bilateral sacroiola. These are sacral insufficiency fractures. I tend to think of these in two different flavors, fatigue, long-distance runners. So let's say you have a patient that comes in, started training for a marathon, trained inappropriately, now they're running, trying to run 10 miles every day, or military personnel that are in bootcamp, rain bootcamp, you name it. So these are basically normal bone that's being pressured by abnormal biomechanics, right? So abnormal stresses, as opposed to an insufficiency fracture, which is more weakened osteopenic bone being subjugated to more normal day-to-day ambulatory stress, walking, getting up, getting the mail. Now, you don't always have to be osteopenic, you can have a variety of pathology that can cause someone to be predisposed to insufficiency fractures, recent delivery, vitamin D deficiency, and so forth. MRI is great. MRI can really kind of help nail down this pathology. The example that I showed you right here can also be difficult to see. So if they're really osteopenic, or they have a lot of osteoarthritis, this finding won't be as easily manifested, which is why MRI can be really, really helpful, because you won't miss this as a radiologist, even as a physiatrist, you'll be able to see that there's increased bone marrow edema-like signal. We see linear signal here to suggest an insufficiency fracture Normal, normal. We can see here on this abnormal side that we can make out the fracture line better on the T1, which will often be the case on any MRI sequence. We'll be able to see fracture lines better because we're not being obscured by as much edema. So these together can be really helpful in differentiating between, for example, bone marrow contusion versus just bone marrow edema, and bone marrow edema and contusion with fracture. You see how there's nice, homogenous T1 fat marrow signal. There's no edema on the normal side, as opposed to the increased edema that we catch here. Normal, normal. T1, stir. Abnormal side, again, same type of finding, right? Nice, homogenous signal. No abnormal stress fracture lines. So next few cases are kind of like clumped together because it kind of goes to a bigger point. So we have a normal radiograph of the pelvis. We see a coned-in view of the pubic symphysis on a T1, or sorry, T2, or stir. How do I know it's T2 or stir? Looks incredibly fluid bright. Looks dark on T1. That is hot, bright on T1. We see this kind of small linear signal right along the anterior aspect of the pubic symphysis. These aren't the best, I'm sorry. They're really motion degraded, but I have other examples, but you can see the same type of T2 hyper-intense linear signal along the pubic symphysis. Case number four, 27-year-old professional baseball player with left groin pain. As we can see here, there's a coned-down image of the left hip, left pubic symphysis. We're showing you a lesser trochanter issue, tuberosity, pubic symphysis, pubic tubercle. And we see this increased T2 hyper-intense signal along the insertion of this musculature. Case number five, professional football player with groin pain. Again, showing you a coned-down image of a pubic symphysis. This is a fluid-sensitive T2 sequence showing increased edema in the left pubic body with increased signal within the musculature attaching to the pubic body. Same manifestation on a coronal view. We know this is a T2 because the fluid looks bright and the fat looks dark. And last but not least, a 34-year-old with groin pain kind of showing you kind of redundant appearance of a myotendon disjunction. What are we really putting it all together? It is athletic pubology. What is athletic pubology? And when I tell my residents and my fellows, it's a wastebasket term, meaning like it's a one-phrase catch-all where we can attribute all sorts of groin pain that includes issues with the pubic symphysis, rectus abdominis, adductor, insufficiency fractures, inguinal wall deficiencies, all-in-one diagnoses. So it's important when I hear a diagnosis of athletic pubology on an MRI, I often don't think of one, I think of multiple pathologies and I end up thinking about multiple different types of scenarios. A common important structure to be aware of is the adductor erectus abdominis aponeurosis. So basically it's like this thick fiber span of tissue that is basically the encompassment of the pubic symphysis joint capsule, adductor musculature, rectus abdominis, the pubic bone. And then really from this thick capsule that can also get injured and cause a manifestation of these types of symptoms. It's involved in everything. I mean, I'm telling you everything, football, rugby, martial arts. There's not a sport I haven't seen it in, right? Because it can involve any of these types of pathologies. This just trying to show you really kind of this area that we're looking at, really within the rectus abdominis, adductors would come in here. So it's a really area of complex pathology or complex anatomy. Just showing you some more anatomy we'll get to here in a little bit. So the most common injury usually involves the adductor muscles, really the adductor longus. And it ranges about from 44, about 60%. And the findings really range from like low grade strains to complete muscle tears. And it really, really, it really depends. You can often get isolated injuries of the rectus abdominis, but usually they come in a package, right? Usually you don't injure just one because there's such an intimacy of the aponeurotic plate. If one finding can often bleed into the other finding. And these we'll talk about here in a quick second. So these are just some cases that are revisited. Anatomy, we have some T2, T1, fat is bright, fluid is bright on a T2, fat is bright on T1, obturator externus, internus, pectineus, and then the aponeurotic plate or that kind of anterior pubic symphysis joint capsule. So we look here, we see that kind of linear signal. Take my word for it if you can't see it, it's there. Basically we're catching a tear in the aponeurotic plate as opposed to a normal side where we see a nice hypotense signal. Okay, this was our baseball player. Again, pectineus, obturator externus, internus, we're getting a T2 view of the left hip. And really we're showing you what? Fluid bright signal where a tendon attaches. When I think of a fluid bright signal at a tendon attachment, I think tear. And that's exactly what this is. A low grade tear of the pectineus at the pubic tubercle insertion or attachment. Again, really kind of just a low grade example of what I showed you previously. We see reactive edema, likely due to ultrabiomechanics, strain. We see some periosteal edema. Again, the same pathology, right? We're getting either, could be from direct contusion, ultrabiomechanics, all following under the umbrella of athletic pubalgia. And this just showing the examples of a normal, right? I see nice homogenous signal, homogenous marrow fat where I see increased marrow signal here involving the left pubic tubercle. And this just showing you an adductor longus redundant tear. As you can see here, pubic sempsis, iliacus, piriformis. Yeah, I'm sorry. I'm kind of rushing through fight through cases here. I want to make sure that you guys see as much as possible. And then I can always run back if you guys have questions. So we have a normal frontal view of the pelvis, quick anatomy, right, left, heads right here, lower there, symphysis, SI joints. This is the anterior inferior iliac spine, right? Which serves as a direct attachment or direct origin of the rectus femoris. In case you don't know, this rectus femoris has two origins, direct anterior inferior iliac spine, and the indirect is a supracetabular origin. Looks great. But let's focus out here on the right greater trochanter on this coronal T2 sequence. We see tons of edema along the right greater trochanter. Axial, again, showing you the same T2 sequence showing irregularity of the greater trochanter. This is a gluteal tendon tear, underlying cause. It really is just chronic repetitive micro trauma, tendinosis, you know, trauma, fall. Seen in many, many athletes, but mainly runners and ballerinas. The important thing to really understand with the greater trochanter is that there are multiple facets, right? So the anterior facet is home to the gluteus minimus, while the lateral and posterior lateral facets are to the medius. And you can often make those diagnoses of which tear it is depending on where the pathology is. Oftentimes, again, one bleeds into the other. You know, the greater trochanter is really the, you know, the shoulder of the hip as we call it in radiology, right? Because the way I look at a shoulder MRI, the way I look at a gluteal insertion of the trochanter, you can get tendinosis, you can get bursitis, and you can get tendon tearing. So we're looking at the minimus, medius. We see increased signal here, irregularity of the, you know, tuberosity. Again, anterior facet, lateral, posterior lateral facet, and posterior facet. Minimus, medius, medius. And if we can see here, most of the minimus is intact. However, as we get to the more of the lateral and posterior lateral facet, we see a predominant tear of that gluteus medius as it inserts. We only have like a minute left here. Yeah. So I know you had a lot of slides and thank you for going over them. Yeah, no problem. Just so we can have some time to answer some of these questions that have come through. So next, for unilateral hip pain, do you typically prefer a pelvis MRI over a unilateral hip MRI? So you can compare side to side as you did with the piriformis case? Yeah, that's a really great, great, great question. So I recommend getting a pelvis MRI if they can, have them do a dedicated MRI or sequence of that right hip. I'll give you a really good example. In athletic prebiology, you can often get pain that results from the pubic symphysis that translates into groin pain. And if we don't get visualization of the pubic symphysis because they're so focused in on their hip, we may be missing potential pathology that we could address. So get a pelvis MRI, and if you can, get a couple of sequences that are more dedicated to the hip. Great, and then there was one question asking, what is the magic angle on the stero sequence? So the magic angle is 55 degrees. And on certain sequences, you'll be able to look at, let's say, let's say you're looking at a gluteal tendon. I'm just gonna use a gluteal tendon as an example, because we were talking about gluteal tendon tears. So you'll often see, looking at tendon, you'll see tendon that has, it'll look like it has increased signal, right? And when you see increased signal like PD signal, you know, fluid bright signal, you'll often be confused thinking that there might be tendinosis. But when you have a ster sequence, it can help negate that. It'll make the tendon look more what it should like, more normal. And so you're not gonna be tricked into thinking that there's some sort of tendon pathology when there really isn't. So that's what I mean by ster can kind of circumvent the issue of the magic angle, which happened at 55 degrees. It's just a weird, you know, weird phenomenon that we find where tendons look abnormal, looking bright, brighter than they should. Great. There's a question asking the surgeons that they've worked with prefer MRI arthrogram for rolling out labral tears. Do you feel like MRIs without arthrograms are typically sufficient? No, I don't. I mean, I know the reasoning for it. I know there's a big push at HSS. You know, Dr. Potter does phenomenal work out there. The only issue that I have is that in the rural setting, in the community setting, you may not have MR machines that are able to give you the same level of detail, the same level of like anatomic detail. If you can put fluid in there, you can really manifest those subtle labral tears, right? If you don't, it can make things difficult. I'll show you a really quick example. I know I have tons of stuff here, but... So we look here, for example, this is just a normal MRI arthrogram of the hip, right? Sagittal PD. I can make out really good that that's a sharp triangle. But when I don't have that, it's often very, very difficult to make out these subtle abnormalities, right? And sometimes these delamination tears are really, really tough to see without getting an arthrogram. So if you can, please get the arthrogram because you may not have all the, you know, sequences that a major institution has or the firepower of a newer scanner to really, you know, see those fine details without an arthrogram. Great, thank you. I know we've gone two minutes over and sorry to cut you off, but I think I have to let everyone go, but thank you so much for presenting. And thanks everyone for coming out. And hopefully, you know, you guys found this helpful. The idea behind this is to hopefully each year do a different joint to kind of go through and go through both x-ray and MRI. And so hopefully see you guys all next year for the rest of your conference.

Musculoskeletal Radiology Fundamentals

hip

pediatric HIP x-ray

adult HIP x-ray

MRI of the HIP

normal anatomy

pediatric HIP pathology

osteaoarthritis

femoral acetabular impingement

MRI evaluation of the HIP