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So this was a case of hip arthroplasty.

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And as we can see that there is abnormal soft tissue around the hip

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arthroplasty, which is, it looks like a ated fluid. It has this really thick,

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uh, dark, uh, rim. And then there is like irregular, uh,

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soft tissue density inside. So it looks like a,

0:19

a thick wall fluid collection with debris inside. And, um, I'm sorry,

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I'm not able to bring up the other images. Hopefully this axial will run. Uh,

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so we see that these changes have gone into the medial wall of the tuum.

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The bone is expanded and it's all filled up with this, uh,

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heterogeneous soft tissue.

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So when you have a finding like this with a hip arthroplasty,

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that suggests what is known as adverse local tissue reaction. So what is it?

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It's just an inflammatory response to the micro,

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uh, particles that are shed from the arthroplasty.

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The different components when they glide over each other over time,

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microparticles are shed from the implant.

1:00

And if the body amount amounts and inflammatory response to those

1:04

microparticles, uh, it causes soft tissue destruction. And that's what, uh,

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this is manifestation of. It's the,

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it's the destruction of the surroundings soft tissues because of all the

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inflammatory response that is mounted to the,

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the microparticles that are shed from the arthroplasty or these particles.

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If it's a metal on metal, it'll be metal. If it's metal on plastic,

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it can be metal debris or even plastic debris. And the amount of, uh, the,

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the testt logic response can be little different.

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One is lymphocyte dominant response.

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The other can be a monocyte dominant response, but very irrespective of, um,

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like what we see on imaging is, uh,

1:46

is this soft tissue destruction around the hip arthroplasty. So, uh,

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again,

1:53

I just quickly show you some teaching points on this one just to understand what

1:56

we need to talk about. So,

1:58

adverse local tissue reaction is the umbrella term for local soft tissue

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complications resulting from host reaction to arthroplasty related metal

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products. So adverse reaction to metal debris, also the other term,

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now Val, if you hear of that term,

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which stands for aseptic lymphocyte dominant vascular associated lesions,

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it's a histopathologic description of these changes.

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So radiologic term is adverse local tissue reaction and ve is the histopath

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term.

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Metalosis is specifically when you have changes in response

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to big metallic debris.

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So this is easy to see on MR because these things are going to cause

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susceptibility artifacts. So if you see, uh, uh,

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abnormal soft tissue and it has like really T two dark signal and has

2:46

susceptibility, then you know it's probably metalosis.

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And then this term pseudo tumor is what is has been used,

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uh, for these abnormalities. This was a common term that has been

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Used so far,

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but it's an old term for any mass like solid appearing periprosthetic adverse

3:04

local tissue reaction. So it's, it's, it's a misnomer,

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but that's what we've been using it. And that's the most more common,

3:11

like commonly used term for these arthroplasty related complications.

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But the more accurate term to use is adverse local tissue reaction.

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Val is the histopath term. So, uh, in a painful arthroplasty,

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if we have, um, elevated, uh,

3:27

CRP and ESR that suggests chronic inflammation and if,

3:31

and joint aspiration you have, uh,

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elevated white count is seen both with infection and adverse local tissue

3:38

reaction. But in ALTR the culture is negative.

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And typically these implants will have high cobalt and chromium levels,

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either high cobalt or chromium or both. Uh,

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any any level maybe elevated depending on what type of arthroplasty is.

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And for this abnormal soft tissue, there are certain classifications. There are,

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I think there's um, an Anderson classification.

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Then there is the imperial classification.

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It depends on how that soft tissue is looking.

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If it's more fluid like soft tissue,

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then it's type one and sometimes it looks the,

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the abnormal soft tissue around the implant is completely solid and dark.

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So that will be type three.

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And something in between will be type two and type two B.

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So this was an example of like, this was,

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this is a specific term used trion noses.

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It's again a part of adverse local tissue reaction where you get corrosion at

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the head neck junction, which is known as the trion of the implant.

4:28

So there was erosion here. That's why this implant failed. You, you're seeing,

4:31

um,

4:32

angulation and on MRI you have this lot of abnormal periprosthetic,

4:37

almost like a fluid collection, right? But it's very thick world.

4:39

It's really thick world.

4:41

There is no surrounding edema to suggest a whole lot of inflammation.

4:44

Like we see it in infection and uh, we aspirated the joint.

4:48

The aspirate in these cases is very dark because of, again, metal deposition.

4:53

And uh, even in surgery, the, the tissue that the,

4:57

the necrotic tissue that the debride, it's all coated with metal particles,

5:03

but not all per prosthetics of tissue is ALTR. So to make sure,

5:07

sometimes you can get heterotopic ossification around the implant.

5:11

Sometimes there is complex bursitis.

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Sometimes there is a hematoma seroma and sometimes it can be a neoplasm.

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So not of all abnormal soft tissue around the implant is ALTR. So again,

5:21

we have to look at your t and anti T two weight images carefully and determine

5:24

what we are looking at. So for example, like uh,

5:27

we had one case where the patient had arthroplasty done for a chondro sarcoma in

5:31

the pelvis. And on follow-up Mr. He developed a periprosthetic soft tissue.

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Now that soft tissue didn't look like a fluid. It was more that uh,

5:39

the tumor gray or the evil gray. Um,

5:42

that soft tissue had that signal and it enhanced on post contrast. So we then,

5:46

um,

5:47

in those cases you will like hesitant from saying it's

5:52

adverse local tissue reaction,

5:53

we should say probably recurrent tumor that sounded

5:56

More likely in that scenario and that actually turned out to be tur and was not

6:01

adverse. Local tissue reaction. So coming back to images, uh,

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this is what we are seeing really abnormal soft tissue that gets into the bone.

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So it can cause osteolysis

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and it can even decompress into the bursa.

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So here it's decompressing into the ele lio versus bursa. Sometimes it'll be,

6:19

if the fluid goes more posteriorly,

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it can decompress into the tro enteric bursa.

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So these are your good locations and when they're bright,

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they're easier to locate. But some,

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the type three ones which are more solid and very dark,

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they will blend with this dark signal of arthroplasty.

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So we have to be very careful in determining what's the margin of arthroplasty

6:41

and see if there is any high point and signal beyond the margins of that

6:44

arthroplasty and its artifact. And um, that's when we question that,

6:49

that could be adverse local tissue reaction.