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Dr. P here with a tough case.

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3 00:00:02,949 --> 00:00:05,040 It's a four-year-old with ankle pain

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and tenderness and some swelling.

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And we have a sagittal proton density

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fat suppression image, so-called heavily

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water-weighted sequence on the left.

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Slightly different parameters,

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but basically the same sequence on the right.

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We have the T1 spin echo fat

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weighted image in the center.

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Now what makes this case a little bit

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challenging is trying to sort out the signals

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distal to the growth plate.

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Now one thing you can do is go to

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an area that you know is more normal

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and that is the back of the talus.

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Here's an area that's unossified.

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So you're looking for something that

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sort of matches the signal intensity

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of the unossified talus here and here.

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And when you look up here in

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the tibia, there's a good match.

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So you'd say to yourself, okay, that's

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probably normal cartilage and maybe that's

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abnormal cartilage and maybe that's bone.

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Now, admittedly, over here on the far left,

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on the water-weighted image,

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you've got a rather protonaceous effusion here.

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And if you look really carefully,

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that protonaceous effusion has diffused through and

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interrupted the articular surface of the talus.

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So, we've got something going on, at least

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potentially on both sides of the joint,

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which in your brain should light up a flare.

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You know, septic arthritis,

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septic arthritis, septic arthritis.

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That alarm bell should be going off.

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It's a child.

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Now, let's return to that signal that we said

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was a lot like the normal talar cartilage.

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And when we look at the water-weighted image,

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I'm going to blow it up a little more.

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In no way, in no way is that area like the normal

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talar cartilage.

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So you see how you have to use multiple

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sequences to figure out what is really going on.

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In fact, that is more fluid-like.

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It's a collection of something,

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and in this case, a collection of pus.

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It's a Brody's abscess of the epiphysis.

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Now, what about this area right here?

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This area right here is not this area.

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Now if we go to that same area, that's this,

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and that area is cartilage, that's cartilage.

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And in the front, we've got osseous material here.

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Now maybe there's a little bit of edema in

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that cartilage, maybe there's a little bit

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of edema in that osseous segment, because

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we already know there's some infection

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with a Brody's abscess in the back.

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But let's keep scrolling around for

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some really concentrated hot spots

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on our sagittal water-weighted image.

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And we found another one, right there,

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that looks very different from any

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other portion of the growth plate.

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Let's see if we can corroborate

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it on the coronal image.

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And we can, it's right here.

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In the midline, just starting to peek its

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way out, trying to get into the joint,

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and perhaps getting into the joint.

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Let's keep scrolling.

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Let's keep scrolling around

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and see if we find any others.

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Not really.

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Maybe this one right here.

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But let's move over to the coronal image,

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and look at this area right here.

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That's an interesting area.

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That area looks a lot different than this area.

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See, this area is cartilage, and if we

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look at the normal cartilage, let's see

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what the normal cartilage signal is.

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The normal cartilage signal intensity is gray.

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This cartilage signal intensity is not gray.

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So, while there may not be an abscess present

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here, that part of the cartilage, which is edematous,

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is affected by this infectious process.

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And even the areas that are ossified,

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those too are edematous, so one must assume

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that this subtle gray area that involves

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half of the epiphysis

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is also infection.

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So we've got partially infected

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osseous component of the epiphysis.

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We've got infected hyaline

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cartilage without abscess.

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And then in the back, we have an abscess.

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Let's see what our abscess looks like

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in the coronal projection.

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Here it is.

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Right here.

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You can line it up perfectly.

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That whole thing is a Brody's abscess.

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And then when we look at the rest of

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the foot, there's plenty of hyperemia

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to go around throughout the foot.

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There's hyperemia of the talus, there's hyperemia

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of the calcaneus, and you have to be concerned,

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certainly, about the talus as you move forward.

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You can see on the T1-weighted image,

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the signal is relatively normal, but as stated earlier,

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there is some crossing of the joint,

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so the final dispensation here, the final

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diagnosis is going to be septic arthritis,

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osteomyelitis of the epiphysis with Brody's

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abscess formation, multifocal, involvement of

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both sides of the joint, has to be carefully

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monitored, especially as it relates to the talus,

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which is currently edematous but not destroyed.

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There is a collection in the joint

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to be aspirated and cultured.

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There was no abscess, there was no gas in the

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soft tissues, and that's how you play this case.

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Remember to use structures that you

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know or think are normal as a reference,

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and then go back and cross-pollinate

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your visual skills between different

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projections and different pulsing sequences

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to tease out what's cartilage,

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what's infected cartilage, what's ossified

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cartilage, what's infected ossified cartilage,

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and what is a fluid collection.

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In this case, we had all of the above.

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Let's move on, shall we?

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Dr. P out.