Interactive Transcript
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Case number three is not gonna be a case of a meniscal tear,
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it's not gonna be a meniscal tear, there may be a meniscal tear
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there, but that's not the reason why I'm showing you the case.
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In fact, there is actually a meniscal tear here, but that's not why
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I wanna show you the case. I wanna show you the case for
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a different reason. I wanna start with the sagittal T1 as I always
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do. I think it's very important to get into a habit
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of looking at things. So I'm starting laterally. I'm already noticing that
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there's a little bit of signal in the posterior and lateral tibia maybe
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the anterior lateral femur there, okay, maybe... Yeah,
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maybe some meniscal signal right here, but you wanna look at it on
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a proton density or a T2 weighted, okay, so
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there's something going on there. When I turn to the sagittal T2s.
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Okay, and then look at the marrow. Oh, wow, okay, so I'm already
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seeing marrow edema along the anterior lateral femoral condyle right here.
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Posterior lateral tibial plateau. Okay, so these are likely microtubule
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contusions that have occurred. If I go immediately, I'm also seeing Bone
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Marrow Edema along the posterior medial tibial plateau.
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So there are microtubule contusions, these are micro fracture in the bone.
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Okay, that's what this is. And The patella overall looks okay.
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So I wanna bring Ashley in here to ask question number
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four. Okay, so based on this, what soft tissue structure is injured in
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this patient that has bone marrow edema in both the anterior lateral femoral
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condyle and the Posterior tibial plateau? Is it the ACL, the PCL,
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the media collateral ligament, or the medial retinaculum, which soft tissue
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structure is injured based on the marrow edema findings that you're seeing
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here? Okay, so 89% of people got this correct, the ACL, the Anterior Cruciate
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Ligament, that's exactly right. Okay, good. So this is a pivot shift injury,
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this is a pivot shift injury when you get marrow edema along the
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anterior lateral femoral condyle as in this case, in the posterior lateral
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tibial plateau. That should ring alarms in your brain automatically, okay.
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This is a pivot injury. The ACL will be torn in 100%
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of cases. Okay. In every case that I've seen of this,
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the ACLs has always been at least partially torn if not completely torn,
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okay. This is a pivot shift injury, this happens in people like... Skiers
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or American football players, okay. When a valgus load is applied to
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a knee with a femur, either an internal rotation or the tibia in external
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rotation. Right? So if the valgus load is applied to a flex knee,
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where the femur is internally rotated or the tibia is externally rotated,
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you get this pivot shift injury mechanism where you get
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loading on the ACL and the ACL is pretty much torn. Okay. And
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you get these microtubule contusions in these areas. Now I'm gonna show
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you the ACL, just look at that. Look at this ACL it's thickened, there's
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fluid transecting, the mid substance of it. It's just...
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That's a complete rupture or a complete tear, you can't trace all the
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fibers because you have this fluid discontinuity right here in the middle
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of the tendon... Of the ligament, excuse me. So, this is a complete
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tear of the ACL. With a Pivot shift mechanism with bone marrow microtubule
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contusions along the anterior lateral femoral condyle, the Posterior lateral
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tibial plateau. In fact, the reason why I'm showing you this case,
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is that Bone Marrow Edema patterns in the knee are extremely,
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extremely important. Okay. The Bone Marrow Edema patterns predict the soft
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tissue structure that's injured. Okay, so if you get...
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This is one of five marrow edema patterns that's recognized
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as a classic pattern that predicts soft tissue, this is known as the pivot
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shift mechanism of injury. When you get, if you get marrow edema of the
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anterior lateral femoral Posterior lateral tibial plateau, the ACL is always
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injured. There's four other classic contusions patterns that... I'm actually
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gonna show one of them later on in this talk, but this is
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the pivot shift mechanism of injury. And I wanna show you another
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finding in this case, so this is the medial, and again,
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notice that the posterior horn is double the size of the interior.
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There is a little bit of signal here,
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it's not really going to the inferior or the superiority that... So maybe
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this slightly degenerative signal or equal degeneration within the meniscus
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without the sweet terry. But as we come laterally... Look at the anterior
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horn, the posterior horn, there is a little bit of signal here kinda going
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to superior and the inferior surface there. Okay, it looks a little abnormal,
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seen on two or three slices. If I go to the
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coronal stars to focus on that lateral meniscus there...
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Okay, so yeah, there's a signal here, this meniscus is torn,
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there's a tear that the periphery of this... Of the
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lateral meniscus, the posterior horn of the lateral meniscus. This is anteriorly
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with a meniscus is attaching with a transversal ligament along with a tibial
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root attachment, and then if we go posteriorly, it doesn't look that great.
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This may involve the root, this maybe a root ligament here as well
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on the posterior root about ligament. And you can see part of the...
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It's sort of a complex tear, there's some signal here and there's some
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signal there, so this lateral meniscus is not looking great, okay. So you
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can see the nice microtubule contusions here along the lateral femoral condyle.
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You wanna make sure there's no condyle defects. So this is the marrow,
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this hypo intense dark line is the cortex, and this great intermedia signal
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is the articular cartilage. So you wanna scrutinize this cartilage well,
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I like looking at it at the coronal's the best, especially the medial lateral
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femoral condyle, I think the coronals is the best. For patella department,
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I think the axial is better to look at the articular cartilage,
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you can see the cartilage better, but you wanna make sure that the
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signal is preserved and it's nice and great. You start to see a fluid
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signal, you know that there may be a defect in the cartilage can
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be partial thickness, or if it involves the entire thickness of the cartilage.
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It's a full thickness. Here, the cartilage actually looks relatively preserved.
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When you have intermedia signal within that cartilage, there's debate whether
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that's normal, that could be cartilage generation or early cartilage generation,
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but here the lateral compartment cartilage, I think looks, okay. Okay,
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you can actually also see the ACL, this is the ACL right here, look how
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it's amorphous, it's not well defined, there's fluid all around it,
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this is a torn ACL. The PCL on the other hand,
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which is a dark hypo intense structure is preserved. I can see it
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inserts extra articularly, about the proximal tibia, and If I trace it approximately,
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I can see it inserting right there on the medial intercondylar notch, that's
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a normal PCL, okay. Good, you can see here too look at this
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fibular collateral, create one, maybe create two sprains of that fibular
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collateral ligament approximately, okay. Other findings here as well.
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Come back to the sagittal. We can again, take a look at these
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here, there is probably a small joint effusion, this is more than just
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physiologic, there's likely a small super patellar joint effusion. The quadriceps
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tendon looks intact. The extensor magazine, the patellar tendon, I think
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probably looks okay, there is a little bit of pre patella soft tissue
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edema here, along the posterior joint capsule here. So those are all findings
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that you wanna kinda take a look at, when you're reviewing a case
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like this. Okay, so this is a pivot shift injury, they can be
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associated with meniscal tears... Meniscal... Both medially and laterally.
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In this case, we had a lateral meniscal tear, but the pivot shift
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is, 100% of the time is associated with an ACL tear,
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as we saw in this case. The Anterior Cruciate Ligament is torn. When
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you have... The moral of the story, and this... The teaching point here
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is that when you have marrow edema along the anterior lateral femoral condyle,
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posterior lateral tibial plateau as in this case, the ACL is totally torn,
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in those cases. Okay? Alright, good.
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