Video summary
The video focuses on the sixth extensor compartment of the wrist, which is clinically significant as it is the second most commonly affected area after De Quervain's disease. This compartment houses the extensor carpi ulnaris (ECU) tendon and functions as a fibro-osseous tunnel formed by the distal ulna and its associated sheath. A critical diagnostic tip provided is the importance of asking patients to mark their pain location during an MRI; if the marker is on the ulnar side, clinicians should specifically investigate issues related to the TFCC or the ECU tendon rather than getting distracted by minor incidental findings elsewhere in the wrist.
Structurally, the ECU tendon is secured within its groove by a specialized sub-sheath that sits deep to the main extensor retinaculum. Pathological changes in this area often manifest as tendinosis, characterized by increased signal intensity and bulkiness within the tendon itself, accompanied by fluid accumulation in the tendon sheath known as extensor carpi ulnaris tenosynovitis. The transcript also highlights a specific type of injury where peripheral fibers of the tendon remain intact while a tear runs longitudinally through the substance, effectively splitting the tendon into two distinct parts.
Beyond simple tears or inflammation, the video emphasizes the importance of identifying sub-sheath injuries that can lead to tendon instability. In one case described, although MRI showed minimal signal changes and difficulty tracing the sub-sheath attachment, an ultrasound revealed that the tendon was subluxing or slipping out of its groove. This dynamic movement is a crucial finding that static imaging like MRI might miss without careful correlation, underscoring the necessity of combining different diagnostic modalities to fully understand the mechanical failure of the ECU system. Ultimately, recognizing these specific patterns of injury and instability in the sixth compartment is essential for accurate diagnosis and appropriate management of wrist pain on the ulnar side.
Read the full video transcript
Now moving from there to the next
compartment which is most commonly
affected is compartment six.
This is your extensor carpi ulnaris
tendon. That is your ECU tendon. So
again, very important, second most
commonly affected extensor compartment.
And these are the things which you're
going to see very commonly.
One important thing which I didn't
mention in the beginning, whenever you
are doing a wrist joint MRI, ask them to
put pain marker. Because then if you see
a pain marker on extensor compartment
one sheet, you know that you have to
carefully look for de Quervain's. If you
see the pain marker on the ulnar side,
you know you need to carefully look for
probably TFCC related pain or ECU
related pain. So that gives you a very
clear idea that what you really need to
look into because otherwise you might
see small tiny miny things here and
there everywhere. So pain marker is very
important with the wrist. In moving back
to compartment six, compartment six is
like a fibro-osseous tunnel. So your
distal ulna along with the sheet and in
between runs the
extensor
So let's see this. So this is our entire
extensor tendons. One and on the ulnar
side you have extensor compartment six.
So this is your six and this is your
extensor retinaculum which is holding
all the tendons in place, right?
But for ECU, there is a special sheet
which is this red one which is holding
the ECU within the groove related to the
ulna. So if you try to see this above
black band which is going like this is
your
uh
extensor retinaculum. So this black band
is your extensor retinaculum. But you
see this thin black band deep to it
running across like this, this This your
ECU sub-sheet. So this is a sheet which
is holding the ECU tendon in place. So,
you whenever you're looking at the ECU
tendon, you need to look at this area
also carefully.
Again, once you start to analyze the
spectrum remains same. Here you see that
there is increased signal within the
tendon and which looks bulkier as well.
So, this becomes tendinosis along with
this tendon sheath fluid, we call it
extensor carpi ulnaris tenosynovitis.
Then another case which we saw in the
beginning as well. So, here is ECU
tendon. Few peripheral fibers are intact
over here and there is this tear which
is running through and through through
the extensor carpi ulnaris tendon.
Right? So, this is your extensor carpi
ulnaris tendon tear, which is split tear
because the tendon is split into the two
parts. Then you can specifically have a
sub sheath injury. So, if you see this
tendon has some increased signal, but
very minimal, right? But if you try to
trace the sub sheath, which I can do
over here, here, here, here, but I am
not really able to figure out this
attachment over here and there is some
edema over here. So, uh then an
ultrasound was performed to this patient
and the tendon was subluxing out from
here a little bit. Uh unfortunately, I
don't have put the video over here, but
that's the importance of ultrasound
because you can see the dynamic things
as well. So, this is a sub sheath injury
which is let leading the tendon to
sublux out. So, which you need to pick
up and look carefully for.