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Wk 2, Case 3, Knee MR - Review

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This was a teenager footballer knee injury.

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So here besides the, uh, fibro anoma obviously,

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which can look somewhat ominous, uh,

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especially when large in some patients along the posterior aspect,

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eccentric located at the proximal tibia. What we have here in this case is,

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uh, uh,

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a mildly displaced avulsion fracture of the

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ACL uh, footprint, okay? Right here.

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And we see those ACL fibers attaching upon this, uh, uh,

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actually quite, uh, large, about almost three centimeter, uh,

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fracture fragment. Okay? And obviously, uh, uh, you know,

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this could obviously be diagnosed by x-ray,

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but we can also appreciate here that it's slightly comminuted.

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And for those that are interested or like, um, a classification systems,

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there is a Myers and McKeever or a system, um,

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and I think it's three or four grading systems, but basically, uh,

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the more displaced or comminuted, uh,

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these fractures are, the more prob problematic it becomes. Okay?

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And that's a higher grade system. If it's a,

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if it's a large fragment that's non-displaced, um, uh,

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lower grade injuries like type ones, sometimes they'll, even the,

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those lower grade injuries, they, they can manage those conservatively.

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But if it's a higher grade injury where it's more displaced or comminuted,

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that is a type three or type four, um, that's gonna be more problematic.

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And that's gonna be, uh, that's typically gonna require surgery.

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The surgeon's gonna wanna go in there and fix that to prevent, uh,

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instability of the knee. Okay? So that's just a,

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a nice case of an ACL, uh, a displaced ACL avulsion fracture.

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Uh, that's, uh, probably gonna require fixation in this case.

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I guess the other thing that I can also highlight on this case, okay,

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is notice here that, uh, notice the common footprint w uh,

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of the ACL with the angio horn of the lateral meniscus right here.

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So it's a common footprint. Um, and, uh,

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if you're reading MRIs of the knees, you may see, um,

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sometimes cystic degeneration, uh,

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or cystic change of either the distal ACL or even the, uh,

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anterior horn. And then you'll see some cysts, uh,

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running anterior to the anterior horn to the lateral meniscus.

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And you may be tempted to call, uh, anterior horn lateral meniscal tear,

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but that's sometimes just, uh, some, uh,

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ganglion cyst that are associated with those common footprint of those two

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structures.

Report

Patient History

14M football player, knee injury

Findings

Cruciate Ligaments: High-grade sprain of the ACL with fragmented avulsion fractures at its insertion on the tibial eminences and the intercondylar notch.

PCL is buckled but intact.

Bones: Passive anterior tibial translation.

Contusional mildly depressed osteochondral fracture at the anterior weightbearing surface of the lateral femoral condyle at the terminal sulcus.

Contusion nondepressed osteochondral fractures involving the posterior weightbearing surfaces of the tibial plateaus.

Well-circumscribed, subcortical, lobulated, polycystic lesion located in the posterior aspect of the proximal tibial metadiaphysis with a narrow transition zone and associated osteoedema, without cortical breakthrough or periosteal reactions measuring 1.4cm x 1.8cm x 4.5cm (AP, transverse and CC) with diffuse enhancement and a thin sclerotic rim in keeping with a nonossifying fibroma (NOF).

Menisci:A 3 cm vertical longitudinal tear involving the upper surface of the medial meniscus body and anterior horn outer edge with disruption of the meniscocapsular junction and meniscofemoral ligament in keeping with a ramp 2 lesion.

Lateral meniscus is intact.

Medial Collateral Ligament: Low-grade sprain.

Lateral Collateral Ligament Complex: Torn arcuate and popliteofibular ligaments. Low-grade sprain of the popliteus myotendinous junction. Fibular collateral ligament and biceps tendon are intact.

Medial Compartment: No chondromalacia or osteoarthrosis. No osteochondral defects.

Lateral Compartment: No chondromalacia or osteoarthrosis. No osteochondral defects.

Anterior Compartment: No patellofemoral dysplasia. No patellar dislocation or subluxation. No osteochondral defects, chondromalacia or osteoarthrosis.

Extensor Compartment: Normal patellar and quadriceps tendons.

Flexor Compartment: Normal.

Unremarkable neurovascular bundle.

No soft tissue masses or cysts.

Large joint effusion/hemarthrosis without internal debris or free bodies.

Diffuse periarticular soft tissue swelling.

Impressions

1. Right knee pivot-shift injury with sprain of the ACL that remains attached to a fragmented and avulsed fracture at its insertion on the tibial eminences in the intercondylar notch. Passive anterior tibial translation.

2. Depressed osteochondral fragment of the anterior non weight bearing surface of the lateral femoral condyle at the terminal sulcus and the contusional nondisplaced microfractures at the posterior weight bearing surfaces of the tibial plateaus.

3. A 3 cm ramp 2 lesion of the body and anterior horn medial meniscus with disruption of the meniscofemoral ligament.

4. Torn arcuate and popliteofibular ligaments with low-grade sprain of the popliteus myotendinous junction at the posterolateral knee corner.

5. Large joint effusion/hemarthrosis with no internal debris or free bodies. Diffuse periarticular soft tissue swelling.

Case Discussion

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Gitanjali Bajaj, MD

Assistant Professor

University of Arkansas for Medical Sciences

Edward Smitaman, MD

Clinical Associate Professor

University of California San Diego

Brian Y. Chan, MD

Assistant Professor of Musculoskeletal Radiology

University of Utah

Todd D. Greenberg, MD

Radiologist

ProScan

Tags

Musculoskeletal (MSK)

MRI

Knee