Interactive Transcript
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This is a 22-year-old man with knee pain.
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He's had prior ACL surgery.
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They can either perform this surgery
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using some hamstring,
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they can use patella,
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or they can use cadaveric tendon.
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And this patient,
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you can tell right away from the axial projection,
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there's a defect in the anterior patella.
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So they have used bone, tendon bone,
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the other piece of bone coming from the tibia or
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an autograft to make this new ACl for this
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patient. Now, there are some advantages of this,
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namely the longevity of the graft as opposed to,
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say, cadaver, which may last a little less time,
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but the recovery period is a lot easier when
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you use cadaveric, non native acl.
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As I scroll up and down,
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this patient's got a small effusion and quite a
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bit of scarring anteriorly or low signal
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intensity in the axial projection.
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And you can see the graft as this linear structure
0:59
along the lateral aspect of the femoral notch.
1:01
And the femoral notch is fairly generous in its
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breadth or diameter from side to side or width.
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let's look at the sagittal projection.
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And one of the things I do in somebody that's had
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an autographed is I look at the character
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of the patellar mechanism,
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because when you harvest tendon from the patella
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and then take a strip of tendon down to the tibia,
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the patella will often overgrow,
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it'll get too big,
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and sometimes that leads to patellar tendinopathy.
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That is one of the complications of using
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a bone tendon, bone autographed,
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or a piece of patellar tendon.
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And this patient actually has it.
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They weren't born with a pointy inferior patella.
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Now, that may not be problematic today,
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but that can be problematic in the future.
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And that's one of the reasons why I personally
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would go for a cadaveric graft at my age,
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and many people would.
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The quadriceps tendon usually
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isn't affected in patients that are harvested
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because the harvesting usually occurs right
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about here and then the strip comes down.
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The other thing I like to look at is the character
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of the patellar tendon. And admittedly,
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it's a little hazy. It's a little thickened,
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but there's no focal tear on
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the water weighted image.
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There's a little bright signal
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right under that spur. Again,
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the patient isn't symptomatic there yet.
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There's also a little bit of signal intensity
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at the patellar tendon insertion.
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And I would comment on that
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in the body of the report,
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and there's extensive scarring at the site
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where the clinician has entered the knee.
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Now,
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another caveat when you're looking at patellar
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harvesting is to look at the length of the
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patellar tendon, because it can contract.
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And this is one of the causes of patella baja.
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In other words,
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a patella that's pulled down from scarring
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of the infra patellar tendon.
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And this one is a little bit short.
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I like to see the length of the patella and the
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length of the patellar tendon about one to one.
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And just eyeballing it,
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I think you would all agree that the patella
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is substantially longer than the tendon.
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So you would say that there is a tendency
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for patella baja in this patient.
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But let's move on to our graft.
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Now, there are a few ways to look at the graft.
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the conventional way would just simply be to do
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your standard orthogonal views and hope you catch
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the graft correctly, which, by the way, we did.
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Another way to do it would be to look at the graft
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and then angle with the graft distally, and then,
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if necessary,
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make a second angle along the femoral tunnel so
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that you can see the intra tunnel portion or
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the intraskeletal portion of the graft.
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You only need to really do that in complex cases
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where there's definite graft laxity.
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This patient had pain but not locking
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and not any known instability.
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Or you may have to do it as part of an
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add on or bring back examination.
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Another technique that you might use,
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especially in difficult cases where there's
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extensive swelling, scarring,
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and the graft is hard to really discern,
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is you might take an axial oblique that's
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perpendicular to the graft, like that,
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so that you can see the graft in cross section and
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assess its overall diameter from top to bottom.
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Now, let's take away this line,
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and let's look at where our
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graph should be placed.
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Our graft should be placed as close as humanly
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possible to this line right here,
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which is the posterior femoral line.
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So we bring that line down,
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and then at the intersection between
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that line and Blumenstadt's line,
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which is going to be right here,
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that's where as close to the cortex as possible,
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the femoral tunnel entrance should be drilled,
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which takes a fair amount of courage and talent,
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because you are right subcortical,
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you're right next to the cortex.
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So a lot of nervous nellies may take that hole
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and put it too far forward or too far down.
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And that is a lot worse than moving
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the tibial tunnel around.
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This is the more important of the tunnel
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entrances. Now, the tibial tunnel,
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I give a fair amount of latitude to that tunnel.
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I like to see the tunnel a little further back.
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If the roof is very vertical,
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I like to see it forward a bit.
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If the roof were very horizontal.
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What do I mean by a horizontal roof?
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It goes this way, our roof is going this way.
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A vertical roof would go this way.
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So I might put my tibial tunnel back a little bit
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with the vertical roofs so it doesn't get bumped.
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Now,
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another thing I also like to do in looking at my
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graft is look at this distance right here.
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I like to have about a centimeter between the
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graft and the femur when the patient is lying
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on their back. Now, think about this.
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If a patient is lying on their back and this piece
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of bone is already touching the
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trampoline of the graft,
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imagine what happens to the graft
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when they're standing up. Bang.
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It gets slammed every time they jump or run.
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So that is a little pearl,
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a little nugget that is not often discussed that
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you can take away from this brief talk.
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Now,
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I'm sure a lot of you are honing in
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on this structure right here,
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which we'll discuss in a minute,
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but let's just go back to the
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tibial tunnel for a minute.
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I usually take the center of the PCL
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and the center of the tunnel,
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and I like it to be about 2 cm.
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Beta has already stated there's a little bit of
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variability and flexibility here depending
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upon the femoral roof. Now,
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let's go to this structure
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that is a round mass anterior to the Acl.
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It's ill defined on the T1 because it's buried in
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this tissue, which is synovium, and this tissue,
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which is proteinaceous fluid, and this tissue,
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which is synovium. And this is synovium.
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So synovium against the background of proteous
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fluid and synovium makes it
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a little hard to discern,
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a lot easier to discern on the sagittal water
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weighted image about the T2 weighted image.
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Let's have a look.
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Let's go to the T2 weighted image.
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And now it's really easy.
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Now you can see the mixed heterogeneous character
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of this mass, which is known as a cyclops lesion.
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So hopefully you'll keep an eye out for the
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cyclops lesion because it looks
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a little bit like an eye,
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and sometimes it even has a pupil in the middle of
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it. This one a bit more amorphous and ill defined,
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but rather large.
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This is a definite cause of pain.
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It restricts range of motion.
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But despite all that,
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let's look at the position of the tibia with the
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patient on their back. Is the tibia translated?
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So is there passive instability?
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Right. We're not examining this patient.
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So we're not examining this patient
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for dynamic instability,
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but we can assess for passive instability with
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indirect signs like anterior displacement of the
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tibia relative to the back of the femur.
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I like these to line up about 5 mm
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within each other vertically.
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So if I take a line at the back
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of the femoral cortex,
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I want to be within 5 back of the tibia
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on either side, and I certainly am.
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So there is no passive anterior
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tibial translation.
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And I take the sagittal line or the lateral line,
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the line that I just drew,
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and I draw it where the tibia is furthest back.
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So you can see they're almost congruent.
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So this patient does not have passive
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anterior tibial translation.
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It's highly unlikely that they'll have dynamic
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anterior tibial translation as well.
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But there's going to be some micro instability and
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friction going on in the notch because that's
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how you get the cyclops lesion.
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Let's look at a few other findings that
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may catch your eye and define them.
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One finding that may catch your eye is this,
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this vertical signal in the
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posteromedial meniscus.
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How long will that vertical signal persist there?
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Forever.
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How do you know that's not a sign of a new recent
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pivot shift injury? Well, here's one easy way.
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The history. There's no new trauma.
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Why not use what you've been given?
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So it wouldn't make sense to have a pivot shift
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injury without a history of trauma.
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Second,
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if this was a new vertical longitudinal
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tear from another new pivot shift,
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the ACl wouldn't look so good,
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and you'd have some signal above and
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below the area of abnormality.
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No,
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this is a tear with granulation
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tissue that's healing. Now,
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you might say what do you do about it?
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Usually nothing.
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Sometimes if it's very long,
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it's got a lot of length.
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A physician will stitch it,
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but that has become less common now,
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as we've learned that red, red zone, outer third,
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vertical longitudinal tears that are not gapped
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will heal on their own, scar on their own.
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And you certainly can't go in here and take
10:44
out the outer third of the meniscus.
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That's a disaster.
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Let's look at the posterolateral meniscus.
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Do we have something similar?
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Not really,
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but we do have a little bit of swelling at the
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meniscocapsular junction from the original
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pivot shift injury. It's kind of bland.
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It's not very swollen.
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There's no bone injury around it.
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So there has not been a new pivot shift phenomena.
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That being said,
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there are biomechanics here consisting of micro
11:13
instability that are a this graft
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that are producing cinnavitis,
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that are resulting in a cyclops
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lesion and an effusion.
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So this patient has impingement syndrome
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of their ACL graft with a large,
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obvious cyclops lesion best depicted on the T2
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weighted image. Let's do another one, shall we?
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