The Posterolateral Corner: Arcuate and Fabellofibular Ligament on MRI
HIDEInteractive Transcript
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I've got a magnified coronal projection on your left, water weighted,
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an axial T2, also water weighted, but not as much so.
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And a very magnified view of the posterolateral corner.
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There's the lateral meniscus and fibular head, just to get you oriented.
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Where should I start?
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Well, perhaps the axial projection, where we see the medial limb,
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the arcuate limb and the vertical lateral limb of the arcuate.
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There are the two limbs.
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Let's scroll.
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They're barely visible. There's the lateral limb.
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What happened to the medial limb?
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It fused with the posterior capsule
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which consists of the capsule and the OPL, which came from the medial side.
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So medial limb, lateral limb.
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What about the coronal projection?
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We need to go to the apex of the patella to find them.
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There's the medial limb with its arcuate
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shape and the more vertical lateral limb is right there.
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Let's draw over the medial limb for a minute.
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l'll use my pen.
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There is the origin of the medial limb coming from the tip of the head.
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Now I'll take it away, and now I'll put it back.
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Oh, that's tough.
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Now, you have to scroll that a little bit to follow it,
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and most of the time you can't follow it
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because it merges pretty quickly with other structures.
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Here's a little bit of the arcuate, too,
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right there, this linear structure having an arcuate component to it.
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And now in the sagittal projection,
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if we cross-reference these structures, here's the medial limb.
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There's the medial limb of the arcuate
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in the sagittal projection, and then the lateral limb we cross reference.
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And the lateral limb is kind of buried in all this tissue that includes some veins.
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So it's a little harder to see.
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It's a lot easier when there's an injury to identify the arcuate because these
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little wispy structures that make up the arcuate membrane and ligament, will
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retract and fold and get a little bit thicker, and be surrounded by fluid.
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So it's almost as if you have a free arthrogram.
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But the definitive medial limb is seen right here.
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That is the medial limb.
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And you can tell by cross-referencing from the axial to the sagittal.
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And that's how thin it is.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
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