Sciatic Nerve

Subtitles

- The Popliteal Sciatic Nerve Block
is a good block to do for the sciatic nerve
because this is where the sciatic nerve
is found most shallow.
This block can be performed for post year knee pain
after knee surgery, as well as, calf, foot
and ankle surgery.
This is the main nerve that supplies the lower leg.
I find a lateral position gives you good control
of the patients airways if you sedate them
as well as good ergo-dynamics to do the block.
Here we have our patient positioned laterally
with a pillow between the legs for comfort.
To do the Popliteal Sciatic Nerve Block
we use a linear probe.
The linear probe allows us to see structures well
in the shallow plane,
but gives us a wide field of view
to see our needle approaching the nerve.
To perform the Politeal Sciatic Nerve Block
we put the probe directly in the back of the knee.
Placement of the probe in the back of the knee
reveals a structure of the nerve, the vein, the artery.
I call this structure, the snowman in the back of the knee.
You have three circles on top of each other.
The upper most circle represented by the tibial
component of the sciatic nerve.
The middle structure represented by the vein
and the deep structure represented by the popliteal artery.
If we put color Doppler on the screen
we are able to see the pulsating artery
in this area.
Sometimes it's difficult to see the popliteal vein
because this is a low-flow state,
such as we see here.
To visualize the popliteal vein better
we can squeeze the back of the calf,
increasing venous flow through the popliteal vein,
such as this.
There we can see increased venous flow
through the popliteal vein represented better
by color Doppler.
Now, as I mentioned, this is only the tibial component
of the sciatic nerve.
We wanna get the nerve where it comes together
and has both components, the peroneal
and the tibial component.
As we scan up the leg, here we now see
the peroneal component laterally,
the tibial component medially,
the popliteal vein and popliteal artery.
On the medial side we see the semitendinosus
and semimembranosus muscles.
On the lateral side we see
the biceps femoris, long and short heads.
As we keep going up the leg
the tibial and peroneal components join into one nerve.
Sometimes we block the nerve at this level
where the two components are joining.
This allows us to get both components
with a single injection at the nerve.
My needle approach for these blocks
are gonna be from lateral to medial.
What I typically do is measure the depth
of the sciatic nerve in this setting.
Here the sciatic nerve is approximately
one-and-a-half to two centimeters deep to the probe.
So if I measure one-and-a-half to two centimeters deep,
my needle is gonna come in completely perpendicular
and have a very bright view of the needle
and needle shaft as it advances to the nerve.
Now, I typically like to inject deep to the nerve
as well as superficial to the nerve
in order to get complete surrounding
of the popliteal sciatic nerve
for the most rapid onset for this block.
Typical volumes used are 20 to 30 milliliters
of local anesthetic.
This block takes some time to onset
and studies have shown even with complete surrounding
of the nerve, it takes up to 30 minutes
for the nerve block to onset in most patients.
Here we see the popliteal sciatic nerve
surrounded by the biceps femoris laterally
and the semitendinosis/semimembranosis medially.
Our needle is advanced directly above the nerve
and the local anesthetic is injected,
pushing the nerve deeper.
We then withdraw the needle
and readvance the needle again close to the nerve
so we can get local anesthetic spreading
to the medial side of the nerve,
which is more of the tibial component.
Now you can visualize both the peroneal and tibial component
with a local anesthetic completely surrounding the nerves.

Brightcove ID

5508136021001

https://youtube.com/watch?v=X0wqmWXEcTg

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How to: Subgluteal Sciatic Nerve Block

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Dr. David Auyong reviews scanning techniques and sonographic landmarks for an ultrasound guided nerve block .

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Subtitles

- The Sciatic Nerve Block can be used for surgery of the
leg, knee, foot and ankle.
To do the Sciatic Nerve Block,
you can block it at the Popliteal region
or you can block it higher.
Some benefits of blocking it higher
are to be above the tourniquet,
so you don't have to worry so much about nerve ischemia.
You may also get the Posterior Femoral Cutaneous nerve
of the thigh, which comes off very high on the Sciatic nerve
and it's also medial to the Sciatic nerve, as well high up.
This way, you can cover any kind of pain of incision
in the upper thigh area.
To position patients for Subgluteal Sciatic Nerve Block,
we position the patient lateral.
This way, the patient is comfortable,
they can be well-sedated and you can place a probe
on the posterior side of the leg and advance the needle
from lateral to medial.
The probe we use for a Sciatic Nerve Block
is a curvilinear low-frequency probe.
The reason we use this probe is because
it penetrates deeper and this is useful in larger patients.
So some of the landmarks we use
for the Subgluteal Sciatic Nerve Block
are the Greater Trochanter laterally,
the Ischial Tuberosity medially, and
directly in between these two is where we place the probe
The initial view we see is the Greater Trochanter
on the left side of the screen.
On the right side of the screen,
we see the Ischial Tuberosity.
There is a large muscle, the Gluteus Maximus
at the superficial level of the screen.
Underneath the Gluteus Maximus is a hyperechoic nerve,
the Sciatic Nerve.
Between the two bony landmarks is the Quadratus Femoris.
So on this level, the nerve is sandwiched between
the Gluteus Maximus and the Quadratus Femoris.
The nerve here can appear wide, flat or triangular.
It is not a circular structure like some people imagine.
Needle approaches for the Sciatic Nerve Block,
whether is be here, at the Mid-Femoral region,
or higher up at the Subgluteal region,
are performed from a lateral-to-medial approach.
The lateral-to-medial approach usually starts
three to four centimeters away from the probe in this angle.
Now, higher up we'll use the same needle approach.
We can see the triangular Sciatic Nerve here,
and we'll start the needle angle about here.
Now you typically put my nerve
on the distal side of the screen from where my needle
is entering, in order to see the needle better
and travelling across the screen to the nerve.
Typical volumes are 20 to 30 milliliters
of local anesthetic.
Because this nerve is so deep in some people,
some anesthesiologists like to approach this nerve
from an Out-of-Plane needle angle.
And Out-of-Plane needle angle would be in this direction
into the Sciatic Nerve.
Other people like to turn this probe in a longitudinal
direction and see the nerve in long axis.
So here we are turning the probe in the long axis
and following that nerve in the longitudinal pattern here.
So now we see the Sciatic Nerve going down the leg.
The needle approach in this orientation would be in
this angle in plane of the ultrasound beam
down to the Sciatic nerve.
- (Dr. Auyong) Here you can see the Greater Trochanter
on the left side of the screen, the Ischial Tuberosity
on the right side of the screen, the Gluteus Maximus
superficial and a 21 gauge needle
advancing to the Sciatic Nerve.
The Sciatic Nerve is below the Gluteus Maximus
and above the Quadratus Femoris.
Our needle is advancing above the Sciatic Nerve
to attempt to get local anesthetic to spread
to the medial side of the nerve.
Which would be more likely to get the larger
Tibial component, as well as the posterior femoral
cutaneous nerve of the thigh.
Now you can see the nerve, which very hyperechoic,
below the local anesthetic.

Brightcove ID

5508120191001

https://youtube.com/watch?v=IL4qqETpb0k

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Dr. David Auyong reviews scanning techniques and sonographic landmarks for an ultrasound guided nerve block .

Popliteal Nerve1

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Popliteal Nerve

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Popliteal Nerve Bifurcation1

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Popliteal Nerve Bifurcation

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3D How To: Popliteal Sciatic Nerve Block

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3D animation demonstrating an ultrasound guided Popliteal nerve block.

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Subtitles

- [Voiceover] A linear array transducer
with a nerve exam type is used to perform ultrasound guided
popliteal nerve block.
The target depth is approximately 2 to 4 centimeters
in an 80 kilogram adult.
The patient is positioned in a lateral decubitus position
with the hip and knee slightly flexed.
The transducer is placed transversely
on the popliteal skin crease with the orientation
marker directed laterally.
The transducer should be moved medially and laterally
to identify the dark round pulsatile popliteal artery.
The compressible poplital vein can be seen superior
to the popliteal artery.
The tibial nerve lies superficial to the popliteal vein
and appears as a bright hyperechoic oval structure.
The transducer should be slowly translated
up the posterior thigh to identify the point
where the peroneal and tibial nerves join.
The ideal point for needle insertion is at or just below
the split of the tibial and peroneal nerves.
The needles is advanced using an in-plane technique.
The needle is positioned 1 to 2 centimeters lateral
to the transducer and advanced under the transducer.
The initial end point for the needle is immediately
beside the tibial nerve.
Local anesthetic should be principally injected
around the tibial nerve, as it is responsible
for the majority of the innervation of the foot.

Brightcove ID

5764118112001

https://youtube.com/watch?v=9c1A-87maFE

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3D animation demonstrating an ultrasound guided Popliteal nerve block.

3D How To: Gluteal Sciatic Nerve Block

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3D animation demonstrating an ultrasound guided Gluteal Sciatic nerve block.

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