Ultrasound of the Ankle and Foot - HD

Introduction and Objectives

Hello, my name is Sandra Allison
and I will be lecturing on ultrasound of the foot and ankle.
I have nothing to disclose.

The objectives of this talk will be to learn about ankle
and foot structures that can be imaged with ultrasound.
Recognize the sonographic appearance of the normal ankles,
tendons, and ligaments,
and describe the sonographic features of common ankle
and foot pathology.

Posterior Compartment: Achilles Tendon

The ankle is divided into four compartments
and they can be imaged in four compartments.
For the posterior compartment,
we will be discussing the achilles tendon,
which is the structure
that is outlined on blue in this netter diagram.

Now the appearance of a normal achilles tendon is the same
as with any tendon in the body.
Tendons are hyper coic.
They are composed of fine parallel echogenic lines,
which represent collagen fibers.
In this case, we are looking at the achilles tendon
as it comes from proximal
to distal towards its insertion onto the calcaneus.
Now distally at the insertion, we may see an area
of decreased echogenicity in the tendon, which is due
to anisotropy.
To prove that this is not pathology,
we would reorient the tendon by flexing
or extending the ankle
or reorient the transducer
to bring those fine parallel echogenic lines into view,
bring them perpendicular to the beam
and increase the echogenicity in that area of the tendon.

Now, when normal tendon architecture is not seen, one
of the differential diagnosis would be a tendon rupture.
In this case, this patient presented
with acute posterior heel pain, and tenderness
and swelling, and came with a diagnosis of Achilles rupture.
Here we have lost the normal tendon pathology,
that normal tendon appearance.
We don't see those fine parallel echogenic lines.
And instead we see this hyper
to hypoechoic heterogeneous fluid collection in the
expected location of the tendon.
And this is an example of Achilles tendon rupture.

Now, many times you may see a tendonous structure
that is medial to the achilles tendon,
and this is the plantar tendon, which we don't want
to mistake for intact achilles fibers.

Now tendinosis is another type of pathology
that can affect tendons.
In this case, we are looking at a chronic repetitive injury
to tendons that can lead
to muco degeneration in the tendon
and can even progress to tears.
Now here we are looking at the right achilles tendon
and then the normal left achilles tendon.
So you can see on the right the tendon is hypoechoic.
It's thickened. We've lost some
of its normal tendon architecture,
and this is a case with Achilles tendinosis.

Now, measurements can sometimes be useful
because when you're not sure if you're looking at pathology,
you may see that there is a difference
with the unaffected side.
Another thing to point out is that even very small tend measurement differences may in fact be relatively
or proportionately significant, such as in this case
on the transverse view,
the normal tendon has a normal football or ovoid shape.
It is uniformly hyper coic.
Whereas this tendon, which has the tendinosis,
has focal thickening of the medial aspect of the tendon,
which is the more common location for tendinosis.
Also with tendinosis, we may find increased vascularity
with power doppler imaging
and one should always be careful to not compress
or have a heavy hand when scanning so as
to compress these vessels.
During the scan. Now with more advanced
or severe cases, you may completely lose normal
tendon architecture.
So in this case we are looking at achilles tendon
that is significantly or markedly thickened.
It is hypoechoic. We've lost its normal architecture.
Another thing to point out is
that the tendon is not involved that it's insertion,
but rather proximal, closer to the myo tendons junction.
Over time, calcium may form within the tendon.
So this is a case of calcific tendinosis.
You see calcifications within the tendon just at,
near its insertion onto the calcaneus.

Medial Ankle

Moving on the medial ankle, we are looking at three tendons.
The tibialis posterior tendon,
which is outlined in blue flexor digitorum longest tendon,
which is outlined in red
and flexor haliss longest tendon, which is outlined in green
between the digitorum and haliss.
Longest tendons are the structures
that travel within the tarsal tunnel, which is covered
by this flexor reticulum.
And these structures are the posterior tibial artery
and veins as well as the tibial nerve.

The axial view, we are looking at the tibials posterior
tendon up against the medial mais.
Adjacent to that is the flexor digitor longest tendon,
but the flexor lysis long tendon is frequently not seen in
the same view due to anti atrophy.
In between, we are looking at the tibial tibial nerve
and we are looking at the posterior tibial artery
and then the posterior tibial veins, which are right here.

Long axis, this looks just like the other tendons.
We see the fine parallel echogenic lines
and a very hyper coic tendon
as it traverses around the media.
Maus again, as it dives distal to the maus, you can see
that we have a drop in Genicity.
And in order to determine whether this is pathology
versus anisotropy, you'd like to reorient the transducer
and align the tendon perpendicular
to the ultrasound beam.
It is also normal to have a small amount of fluid adjacent
to the posterior tibials tendon just beyond the,
the medial mais and just prior to its insertion.

Now when you see a lot of fluid,
what you might wanna think about is tenino synovitis.
10 synovitis is an inflammatory condition.
We see fluid surrounding the
tendons within the tendon sheath.
We may see thickening of the tendon sheath.
The tendon themselves may look abnormal.
There may be hypoechoic nodular areas within the tendon
or heterogeneity of the tendon.
There is typically increased vascularity during
this inflammatory condition
and you can detect that with power doppler.
You don't always see fluids surrounding the tendon,
but you may see ill definition
of the tendons and tendon sheath.

Now, tarsal tunnel is
An area where the nerve can become entrapped.
So just like with carpal tunnel where you have entrapment
of the median nerve, we are looking at entrapment
of the tibial nerve at the level of the tarsal tunnel.
Here we see a anti coic
to hypoechoic multi lobulated structure
that is in the region of the tarsal tunnel.
This is a ganglion cyst.
Now this patient felt pain,
especially every time they flex their foot.
You can see with the change in the foot,
you can see that this ganglion shifts medially
and will actually displace
and compress on the adjacent tibial nerve.

Lateral Ankle

Moving onto the lateral ankle, we are looking at the
peroneus longest tendon
and the peroneous brevis tendon
on the lateral at the lateral maus and the axial view.
If you want a mnemonic, you can remember
that the brevis is against the bone B brevis bone
and the longest is sitting superficial to
or lateral to the brevis tendon
long axis view the tendons, you can again see
that they're uniformly hypoechoic
and are composed of fine fibrillar echogenic lines
distal to the ulus the longest,
and the brevis diverge with the longest diving deeper
as it wraps around the foot
and the brevis extending towards its insertion on the base
of the fifth metatarsal.

So just like with the prior case,
this patient presenting with lateral ankle pain,
but in this case we have a 10 synovitis involving the
perineal tendons.
So we're looking at the perineal longus
and brevis within their tendon sheath,
and we see fluids surrounding the tendons,
increased vascularity on power doppler, perhaps thickening
of the synovial sheath, and decreased echogenicity
or heterogeneity involving the tendons.

One can't perform interventions when they see
inflammatory conditions of the ankle tendons.
In this case, this is an injection into the lateral
or perineal tendon sheath.
We see these tendons are enlarged.
They're hypoechoic, they're surrounded by complex fluid,
and in this image we are seeing the needle viewed
with a linear transducer in plain
as it is inserting into the tendon sheath
and injecting around the tendons.

Now a special thing that can happen
with a perineal tendon is a subluxation
or dislocation of the tendon.
The nice thing about ultrasound is that the subluxing
or snapping structures can be imaged with a dynamic scan.
So here we have the transducer over the perineal tendons
and we're having the patient perform the maneuver
that causes the clicking in their ankle.

Just to orient you,
we are looking at the fibula over here
we are looking at the brevis pers brevis
and the pers longus.
Now we have the patient perform the maneuver
and you can see now we are looking at three tendons.
So now we are looking at two longest, I'm sorry,
brevis tendons and one longest tendon.
So not only is the brevis subluxed or dislocated,
but the it is also split.
Second, there is fluid surrounding the
tendons within the tendon sheath.

Lateral Ankle Ligaments

Moving on to other causes of ankle pain.
Here we are looking at the lateral ankle ligaments,
which are most commonly involved with ankle sprain.
Here we're looking at the anterior tail fibular ligament in
red, the calcan fibular ligament in green.
Note that it is deep to the perineal longus
and brevis tendons right here.
And we're looking at the anterior tibia
fibular ligament in blue.

Normal appearance.
The nice thing about ligaments is that they are named
after their bony attachment sites.
So here we're looking at the anterior talo fibular ligament
going across from the Alis to the fibula.
The calcan fibular ligament, which attaches to the calcaneus
and the fibula deep to the perineal tendons.
And then we are looking at the tibia fibular ligament
Bridging from the fibula to the tibia.

Now here is a radiology resident who
was playing volleyball over the weekend
and as they landed on their foot,
they felt a pop followed by some swelling.
This is the normal tail fibular ligament
and on this side we see there is fluid deep to the ligament,
superficial to the ligament
and tracking through a defect into the ligament.
The calcan fibular ligament you can see extending normally
from the fibula to the calcaneus just deep to the tendons.
On the affected side, we see
that there is a hypoechoic area which may represent fluid
or abnormal ligament, which was also sprained.
The anterior tibular fibula ligament was normal.

Anterior Ankle Tendons

Moving on to the anterior ankle tendons,
we are looking at the tibialis anterior tendon,
really the extensor lysis longest tendon
and the extensor digitorum longest tendon.
The anterior tibialis tendon has the same appearance
as the achilles tendon and other tendons in the body.
It is composed of fine fibrillar echogenic lines,
which are the collagen fibro, and is hypoechoic.

So this patient presented
with a painful lump on the medial foot
and the original history was to rule out ganglion cyst.
Instead, we see this hypoechoic structure,
and we see that if we look closely, there are
fine hypoechoic lines within the structure.
If you trace it proximally, you can see that it connects
to the tibialis anterior tendon.
So this is a tendonosis of the tibialis anterior tendon.
But if you also look closely at the insertion,
you can see that there's likely a,
a longitudinal split tear within the
tendon at its insertion.

This patient presented with a pop followed
by pain in the anterior ankle,
and when you're scanning the anterior tobi tendon,
you can see it is no longer extending across the joint,
but rather it is retracted.
And you can see that it is
somewhat wavy in its configuration
because it has lost tension.
You can see that it is hypoechoic
and there is fluid in the tendon sheath distally,
we find an empty tendon sheath,
but as we scan more proximally, we find
that the intact portion of the tendon,
this is a normal ankle joint anteriorly.
In the sagittal plane, we have the extensor lysis long
as extending across it,
but this is the area where you would be looking
for ankle effusions.

Heel: Plantar Fasciitis

Moving on to the heel, patients may present with heel pain
and what we'll be looking for is plantar fasciitis.
Now here's the normal plantar fascia.
It has the appearance almost like a tendon or ligament.
It maintains a somewhat constant thickness.
And as you can see here, it is attached to the calcaneus
and it can extend distally toward the toes.
And this is the structure
that we're looking at right here.

Now, plantar fasciitis normally affects the medial
portion of the heel.
And so when you put your transducer right here,
you would start medially to look for thickening.
Now, thickening can occur anywhere
and when it occurs distally,
what we're talking about is plantar fibromatosis.
But proximally, when you look at the plantar fascia,
you're gonna see proximal thickening of the fascia as it is,
attached to the calcaneus.
So here is normal, here is abnormal, normal is hyper coic
and attached to calcaneus, abnormal is hypoechoic
and thickened as it's attached to the calcaneus.
And the patient will tell you
that this correlates with a side of pain.

Other Foot Pathologies

Foreign Objects

Now, ultrasound is also great in evaluating
for foreign objects,
and this is a patient who presents with foot pain
after a barbecue.
The x-rays were negative,
but when you look, you see this linear structure
that is in their small toe,
and this is a patient who has an embedded
toothpick in their toe.

Morton's Neuromas

One other thing that can happen in the foot are Morton's neuromas.
Now patients present with forefoot pain,
and what we're looking for is a mass
in the inter metatarsal web space.
So normal web space is usually hypoechoic
because it is filled with fat.
In an abnormal situation,
you find a well-defined hypoechoic lesion,
which is well-defined.
Oftentimes when you press on this lesion,
patients will confirm that they're feeling pain,
but what you really want to see is you want
to see the entering and the exiting nerve from this lesion.
So here is that neuroma.
Here is that entering nerve and the exiting nerve.

Now, many times, adjacent to the neuroma,
you'll find a fluid distended structure,
and that is the inter metatarsal bursa.
And the whole entity is really a metatarsal bursa, inter metatarsal bursa
and neuroma complex.
So here we see that lesion in the inter metatarsal space
adjacent to it is a hypoechoic
or anti coic fluid collection.
When you compress on it, you can flatten out
that fluid collection and
what remains is the Morton's neuroma

Conclusion

and that ends this talk.
And if you have any questions, feel free
to email me at this address.
Thank you.