All right. I think we are good to go. Good morning, everybody. Thanks for popping on. Thanks for joining. So we are, as was the case last week, we are continuing along with our faculty presentations. Today, we have Dr. Zach Bailowitz. So he is a sports medicine physician in the orthopedics department at Kaiser Permanente in sunny California. He's the head team physician at Cal State University, East Bay, and also clinical faculty for the UCSF Primary Care Sports Medicine Fellowship. We are, I'm excited to have Zach. I've known Zach for a little while and he's a great guy and great ultrasonographer, and I'm sure this talk will be great. He's going to give us a talk on rectus femoris muscle injury. So with that, Zach, take it away. Cool. Thank you, Ryan and Doug for inviting me. Excited to speak about this. I've been doing a little bit more digging into muscle injuries as I've started kind of learning and listening. I realized how primitive my understanding was of muscles and their different types of injuries. So yeah, hoping to just convey some of what I've learned and I continue to learn on this topic. And so yeah, thanks for having me. Can you see my slides and hear me okay? Yeah. Can you make it full screen, Zach? Yeah. There you go. Yeah. Perfect. All right. Perfect. So I have no disclosures. Our outline today, we're going to do a little case presentation. We'll review the complete anterior knee ultrasound exam. We're going to discuss briefly the muscle, a couple of muscle injury classification systems. We'll review the rectus femoris ultrasound appearance, and then I'll do a completed ultrasound report. It does seem like sort of the trend in this series to give some thank yous. So I think the first people I actually want to give a shout out to, I've had some incredible mentors and teachers along the way, but I think the first ultrasound experience and a lot of the learning I did as a resident was with my co-residents. I think for those folks that are listening that are residents, fellows, your co-fellows, your co-residents are really going to be your greatest teachers because I spent hours scanning Nadios and Lauren and really learned so much from that time. So make sure you're taking the time to practice on each other. That experience is invaluable. In my residency, Dave Price, Anthony Martin, and Julian Willoughby all gave me a lot of ultrasound experience. And then Maderic was gracious enough to let me spend some time with him during residency as well, so thank you all. I had great fellowship faculty led by Chris Fisco, and I'm really appreciative. I continue to bother these guys, as they probably know, with ultrasound questions, so thank you all. And then last but not least, the class, the 2018-19 PM&R Sports Fellows. We continue, we have like a group me text thread, continue to talk probably once or twice a week with clinical questions and other banter. And I think that really has proven so valuable in the last couple of years that we all started practice at the same time. We all were kind of bouncing ideas off each other. So make sure that, you know, those of you that are interviewing for fellowship, keep in touch with your class. So this patient that I saw, this was just a few weeks ago. This was a 17-year-old male American football player. During practice, he went to push off and felt a pop in his left anterior thigh. The pain radiated down to the knee. He didn't note significant bruising, but he had some swelling and a palpable nodule in the left thigh. He was able to walk, and even after about a week, started jogging, really with not a lot of discomfort, but he did have pain with any sort of burst-type activities or squatting movements. So I saw him two weeks after his injury. He came into my clinic. I like to kind of be systematic about my approach to the physical exam. So my mnemonic is the IRS Pesters Students, and that's sort of the way that I try to approach everything when it comes to the physical exam. So on inspection, he had a small region of kind of swelling in the mid-substance of the anterior thigh. His knee range of motion was full, but he did feel tight at the end range of flexion. He had some very subtle, slight weakness with hip flexion and knee extension. Otherwise, his strength and sensation was normal. On palpation, he was pretty tender in the anterior thigh, and he had this kind of lumpy nodule feeling, and then he did have some tenderness more distally around the distal quad. From a special test standpoint, I did examine his knee pretty thoroughly, and I didn't notice any ligamentous laxity. He did not have an extension lag. His patellar grind was normal, and meniscal testing was negative. I did examine the hip as well, and he had a positive sting field, but the rest of his intra-articular testing was negative. So from a differential standpoint, you know, at this point, quadriceps muscle injury seemed like the most likely. Certainly, I was wondering about a quadriceps tendon strain or tear at the knee, which is why I did a complete knee exam. Given that he was 17, and I didn't have hip x-rays at the time, I didn't know if his growth plates were closed, so thinking about an AIS avulsion is always something that comes to my brain for these kids. And then, you know, less common, something I wasn't really worried about, but always thinking about femoral fracture or some sort of nerve injury. I did have knee radiographs when I saw him. These are not his, but, you know, I had kind of three views, and I think especially for someone presenting with anterior knee pain, you want to make sure that you've got not only your AP and your lateral, but also this kind of merchant or sunrise view to make sure that you're looking at what the patella looks like sitting there in the trochlear groove. After I saw him, I did order hip x-rays, and again, mostly looking for any sort of AIS pathology, and it ended up being normal. I think, you know, if I had my druthers, I probably would have had this beforehand, and so if you are able to, and patients come in, you know, a lot of the referrals I get from primary care doctors, oh, it's a muscle injury, doesn't need x-rays, and in fact, that makes me want x-rays of two regions if it's a muscle injury in between a knee and a hip, let's say. So, in terms of the protocol that I use, you know, I've tried to sort of model it after the curriculum that came out in 2015, and then I've sort of adjusted my protocol slightly based on this 2022 paper. You know, I always want to be able to identify the stuff that's here in the essential pathology, and does the presentation is, I'll look at some of this stuff in the optional pathology section as well. So, my typical protocol, I'll start off looking at the patellar tendon. During this view, I'll be able to look at some of the infrapatellar bursa and the tibial tuberosity. I'll look at the prepatellar space for a potential bursa there, take a look at the MPFL, the horns of the menisci that are anterior there, and then the quadriceps tendon and suprapatellar recess. I have these other structures here on the right that are sort of more optional that I do depending on what the clinical scenario looks like. You know, I threw IT band on here. I think it's interesting, you know, it's considered part of the lateral exam, but so many of the patients I see with sort of anterolateral sounds, patellofemoral-ish pain, I think that some of those people are having issues with the IT band, and so I try to scan that a fair amount with their anterior knee pain. We did a couple of posters on a dynamic patellar tracking technique a couple years ago, and so I use this a fair bit for my patients if they have like patellofemoral-type symptoms, and then I'll look at the saphenous nerve if it feels indicated, the pes bursa and pes tendons if indicated, and then in our case, we'll be looking at the quadriceps muscle. So we'll start off looking at the patellar tendon. I tried to, Ryan, I tried to sort of copy your box coloration from a few weeks ago. I liked that. So you can see that there's blue and green down here that correspond to these short and long axis views. So this is the patellar tendon and long axis. You can see this nice linear stripy fibular echo texture. It's pretty homogenous, and then you've got the fat pad just underneath. It's important to image all structures, but particularly the patellar tendon in both long and short axis. So this is your short axis view here. You can see the trochlear cartilage is deep to it, and it's important to do that for a couple reasons. You know, these red boxes, these are not, excuse me, not our case, but here's a nice kind of long axis view of a patellar tendon that's hypoechoic thickened here and then has this big old chunk of calcium sitting there that's causing some posterior acoustic shadowing. But if you look in the short axis view here, this was an interesting, I don't see this very often, but the patellar tendon actually had sort of two focal regions of tendinopathy. And if you were planning on doing some sort of percutaneous treatment, whether it's PRP or 10x or a needle fenestration of the tendon, if you didn't look in short axis, you might only see one of these areas in your long axis view and miss some of the pathology. So don't forget your short axis view on the patellar tendon. The prepatellar bursa is the next thing I'll look at. I think one of the biggest keys here is lots and lots of gel. You can see in my normal image here, I've got a good little gel standoff here that you can visualize, and I'm trying to really avoid putting a ton of pressure on. You can imagine that in this clinical scenario where there is a bursitis here, if you put too much pressure, you might displace some of this fluid. So light transducer pressure, lots of gel. I recently learned about the prepatellar space. And so this is actually not something I had heard of until a patient walked in. He said, hi, I'm an avid cyclist and this is what I have. And he handed me this paper and it turns out he was actually correct. And after kind of talking with him and then looking at him and scanning him and then getting an MRI, we sort of confirmed this sort of fascial defect that these athletes who do a lot of repetitive friction can develop. So this is sort of these triple fascial layers that cover the patella and kind of extensions from the quad and patellar tendon. And on ultrasound, you can see on this left side, there's a comparative image of the normal right side. That prepatellar space is thickened, looks a little bit irregular. And occasionally you can see these actual defects like this one on the MRI of the prepatellar fascia. And this one paper actually kind of changed the way I think about this stuff for our big cyclists. They stated that this anterior knee stuff is very rarely patellofemoral pain syndrome and can commonly be this prepatellar friction syndrome. So if I have an avid cyclist with anterior knee pain, I've started scanning this region a bit more. The next thing I'll move on to is the MPFL. The orientation of the transducer can be a bit tricky. I'm typically off at an oblique angle here just a bit, making sure you've got your patella and your sort of distal femur or adductor tubercle in view here. The ligament is typically a bit thicker, kind of more towards the patella and then tends to thin out as it becomes the retinaculum here attaching onto the femur. And then you can perform dynamic maneuvers where you sort of push on the patella if they've had any sort of recent event that might tell you if the MPFL is intact. Interestingly, this is also a place where you can see the VMO fibers coming in here. And there are some papers that describe looking at the fiber angle in comparison to the line of the femur and even have postulated that that fiber angle can perhaps be a clue as to why people are developing patellofemoral syndrome. I'm not typically measuring that angle in my evaluation, but it's something to note. And of course, if you're interested in this, you can take a look at these papers. I do often look at patellar tracking. And so this is a sort of protocol that we developed a few years ago, basically where we have the patient lying supine with the knee fully straight and relaxed. And the patient, you basically are using the patellar tendon as a proxy for where the patellar is sitting in the trochlear groove. And you measure the distance of the midpoint of that patellar tendon from the lateral trochlea. And then you have the patient contract their quadriceps, which sort of mimics some of the quadriceps contraction you might get with running or cycling and see how far lateral that patellar tendon tracks. And so we did some measurements and found it to be relatively reliable in terms of the measurements between raters. And then we also were able to kind of look at normative value. So I look at this sometimes when I'm interested in seeing if there's any sort of maltracking for patients who might have patellar femoral syndrome. You know, I do look at the anterior horns of the meniscus. Admittedly, I don't know that I find this to be too valuable. Certainly, if there's some big sort of perimeniscal cyst or an obvious tear, then you can document it. But to be quite honest, I don't know that I see too much pathology that's worth looking at. But I do know that to be quite honest, I don't know that I see too much pathology that's worth documenting here. I often put in my note, you know, complete evaluation of the meniscus is recommended with an MRI. And then last but not least, you know, I like to take a look at the quadriceps tendon and the suprapatellar recess. I think, you know, when you're looking at the suprapatellar recess, you obviously want to identify the quadriceps and pre-femoral fat pads. The joint space typically lives right in between. Our patient did not have any sort of fusion at all here. One thing that's important, I think, if you look at this quadriceps tendon coming up, if you're in your suprapatellar recess view, it can look a little bit hypochoic here. You might even mistake that for tendinopathy. But I think a lot of that is because when the patient's in their more typical relaxed position, there's not enough tension on the quad. And so, oftentimes, I will flex the knee up. And so, you can see here's the trochlear cartilage indicating that the knee is flexed. And once you see that, you can see that that quadriceps tendon brightens up real nicely here, and we can sort of rule out any tendinopathy. Like we've talked about, making sure you're looking at your images in short axis as well, not only to take a look at the quadriceps tendon, but also this is the type of view you might expect when you're doing an ultrasound-guided knee joint injection. Just a couple of clinical cases here, not our case, but here's a nice example of a quadriceps tendon avulsion. You can see the sort of bite or chunk taken out of the patella here, and you can see a little piece of calcium floating over there. And then, you know, don't forget your dynamic exam. This one I was struggling to tell whether or not it was fully torn. It looks like the fibers kind of approach the patella real well here. And so, if I just play the sine loop here, you can see with contraction, you get a nice dynamic exam that's obviously showing a full tear there of the quad. So, don't forget your dynamic exam there. So, before I go into the rectus femoris and quadriceps anatomy on ultrasound, it's important to highlight a few things, you know, because the rectus femoris specifically is a very unique muscle. As we know, up at the hip, you have the direct head and the indirect head, and the direct head as it extends distally becomes the anterior aponeurosis, so sort of this covering here. And the indirect head becomes this sort of central tendon or central aponeurosis, and that's this kind of comma-shaped little guy right here. And this area right around that central tendon is sort of almost its own muscle. People have described sort of a muscle within a muscle type appearance. You can see this diagram here. It sort of shows them pulling out that central tendon and the surrounding muscle, which is interestingly sort of bipennate, whereas the remainder of the rectus femoris is almost a unipennate muscle. And so, it's important to understand this concept for when we start looking at how the rectus femoris can get injured. So, here's some normal images for contrast of the rectus femoris. This was not our patient, thanks to my current sports fellow, Ryan Way, for letting me steal images of his quad. So, again, trying to sort of show corresponding images with color here. So, this is further proximal, and this is a little bit more distal, but these are both short axis images. I typically will start a little bit more distally. Here, you can see this sort of U-shape here, and then a kind of, it doesn't really look like an A, but it's kind of like an A coming over here. So, it kind of looks like the underarmor sign. And this is a nice view of the rectus femoris, bassus intermedius, lateralis, and medialis. And then, as you go further up, you're going to start to see this central tendon come in. So, you can see a nice, excuse me, normal appearing central tendon. We don't see any evidence of any hematoma or anything around it. And if you look in long axis, you can see the central tendon coming down from the left side of the screen, which is proximal, and it sort of ends up ending kind of right around here. And so, these are the views that I would recommend getting for those sort of mid-quad type injuries. So, before we can, and I'm sorry, I got a little something in my throat here. One second. Before we can determine the type of injury that they sustain, we kind of need to think about what types of injury classification systems exist. You know, when I was in med school, it was sort of like, oh, if it's a small tear, it's a one. If it's a medium tear, it's a two. And if it's a big tear, it's a three. And that was sort of the way I understood muscle and tendon injuries to be. And so, I think this was from 2013, if I'm not mistaken. This was the Munich consensus statement. And they sort of described functional muscle disorders versus structural muscle disorders, where an actual tear may be something that's either a type three, where it's minor or moderate, and those are A and B, and then a type four, which is kind of a full tear. I haven't found this to be too helpful. And so, I typically use the British Athletics Muscle Injury Classification, or BAMIC. And this was a relatively novel classification system when it came out, because not only did it classify based on the size of the tear, it also used a letter to denote the location. And this is key, because what we've started to learn is that the location of the tear, is it myofascial, is it musculotendinous, or is it intratendinous? These types of tears can determine the prognosis for the injury. And so, this was really a real landmark paper when it came out, and something that I continue to use when I'm trying to classify these. Now, of note, as you can see, this is a hamstring here, not a quad. And I think one of the challenges is that these classification systems are based on certain muscles, and they don't, it's not a nice, perfect fit for every single muscle that exists. And so, for the quad, as we'll get into it, maybe it's a little challenging, but we try to fit into this box if we can. And again, here's just a nice visual representation. You've got the myofascial injury here, more on the outside, where that kind of fascial layer is. Musculotendinous injury, where you see the injury to the muscle abutting the tendon, but not into the tendon itself. And then here's the tendinous injury. And as you can see, with tissue healing time, it does get higher depending on this grade. Now, how does this affect prognosis? Well, this paper was from 2009, so this predates our BAMIC classification. But these guys looked at sonographic prognosis of rectus femoris injuries, and they divided it up into distal versus proximal, as well as looking at the length. And they found that higher grade, longer injuries, and the more proximal they were, resulted in longer absence. Unfortunately, since then, there haven't been a lot of prognostic papers on the rectus femoris. Most of the data that we have now looks at hamstring. So this was a paper from 2016 using that BAMIC classification. And as you can see, the higher the classification on BAMIC, the longer the return to play time seemed to be. This paper just came out last year, or no, sorry, this year. And they stated in theirs that they found that hamstring injuries extending into the intramuscular tendon did not seem to influence time to return to play. But I thought it was interesting because they don't have in their cohort, they didn't have any grade three C injuries. And grade three C are the ones that extend into the tendon for a grade three. And so I didn't know if their conclusion was really completely valid. But again, you can see the BAMIC classification does seem to correspond with kind of time to return to play. So have there been descriptions of rectus femoris injuries? Not many. This was, believe it or not, all the way back in 2002. Here's our sort of some of the early pioneers, Bianchi and Martinelli. And they sort of described three types of rectus femoris injuries, these sort of more focal peritendinous injuries, kind of more diffuse peritendinous injuries, and then kind of a complete tear. But again, this is well before BAMIC and honestly, well before I was even holding an ultrasound transducer. So these guys have really done an incredible work for how long they've been doing this. I think one of the most interesting papers I've seen on these types of injuries is this from 2014 that looked at MRI findings and described this sort of novel concept of a degloving injury. And so this goes back to that concept of the muscle within a muscle. So again, you've got sort of the whole rectus femoris here, but you can see that that central tendon and the surrounding muscle almost looks like it's separated from the rest of the rectus femoris. And you can see down here, there's even a little hematoma where that central muscle area was just sort of yanked and pulled proximally. This one over here, not as severe. You don't have that big hematoma and surrounding separation, but you can still see some surrounding edema of that central tendon, as well as this kind of fuzzy hyper-intense appearance here that indicates that there may have been some traction on that central muscle. I tried to look for rectus femoris degloving injuries with ultrasound and there is nothing. And so certainly an area where more research may be needed. And I know that some of the folks over in Spain have been looking at this a little bit, and I think Maderek has looked at this a bit. So hopefully we'll get some more data on this soon because it's something that I have started to see. So here is our case. And we'll start off kind of in the middle here. You can see that you've got this kind of central region, the central tendon sits here in the middle, and you can see that the musculature surrounding that central tendon is kind of hazy. We don't have that typical muscle appearance that looks striated with the perimusium. And then you've got this sort of hypochoic almost surrounding region here. We don't see any significant hematoma there, but then as you scan proximally, you start to see this hematoma develop here, which kind of sits just adjacent to the central tendon here. And then in the long axis view, no hematoma where that degloving injury starts down here, but you can see the central tendon is a bit wavy because it's not quite on tension. And then you've got this kind of fuzzy hypochoic region surrounding that kind of central muscle. So here's a couple of clips. This is first going to be going from distal to proximal. So you can see this sort of, here's our underarmor sign, normal appearance down here, and then you start to notice immediately some kind of ugly appearance of this rectus femoris here. You've got a little hematoma there on the lateral side here. I'll play that again. Again, normal musculature, and then you start to notice some hypoechogenicity, the loss of that normal architecture, and then some hematoma over here. Now, as we look proximally, you can see this big hematoma sitting here that's just adjacent to that central tendon. And as we scan distally, we can appreciate that there's a little hematoma there on the left as well. Again, with that kind of loss of normal architecture. A couple of companion cases to compare this to. First of all, this was a patient who came in, their injury was months ago or years ago, I don't remember, but you can see it obviously looks much different. There's hypoechoic, this is scarring here. Here's the very edge of the central tendon. So this is much more distal, further down towards the knee, not involving that central tendon or any sort of that central muscle slip at all. And then this is a nice example of a myofascial injury. So the central tendon is over here, it looks normal, but here you can see this area of muscular disruption along the outside. And so that's a myofascial injury, which is a lower grade based on BAMIC. I'll play that one more time. Lower grade based on BAMIC. And so, again, a nice way to be able to say, okay, I'm not sure that this is quite as severe as what we might see in other patients. So how do we describe this? Again, I like to put the indication here, comparison images, the transducer and machine I use. And so my description was that there is a degloving type injury of the central portion of the rectus femoris muscle without associated injury to the central tendon itself. There's also a more proximal rectus femoris musculotendinous tear with associated hematoma. It comprises less than 50% of the muscle cross-sectional area. And so we can characterize this as a 2B injury based on BAMIC classification. And then the rest of the report was normal. And so my impression here is down at the bottom, a rectus femoris muscle degloving injury without central tendon injury. Now I have to say, I was chatting a bit with Wes Troyer last night, who does a lot of muscle injury scanning as well. And we had a really esoteric and nerdy conversation about whether or not the 2B classification makes sense. Because if it's really a muscle within a muscle, maybe that's more of a fascial injury than it is an actual musculotendinous injury. And I think the challenge here again, is that this BAMIC classification is based mostly on hamstring injuries. And so trying to take a hamstring injury classification and apply it to a different muscle that has a unique structure can be challenging. And so understanding that we're trying to fit all these muscles into one small box and it doesn't always work, but doing the best to explain your rationale when you're describing these so that people understand where you're coming from. And I think that that can be really valuable. So yeah, this was my classification. I was able to give this guy a little bit of data at least to tell him what type of injury he sustained. And yeah, hopefully that was valuable to him. So that's all I've got here are my references and thank you very much.

3rd Edition, Case 01

3rd Edition

Abdomen

rectus femoris

sports medicine

muscle injury

ultrasound diagnosis

BAMIC system

Dr. Zach Bailowitz