Femoral Nerve Block

1
Femoral Nerve Block
2
Femoral Nerve Origin

• The femoral nerve is the largest branch of the
  lumbar plexus, and is formed from L2,3,4.

3
Femoral N. Anatomy
4
Femoral N. Anatomy Key Points

• VAN vein, artery, nerve (from medial to
  lateral).
• Nerve lies on top of iliopsoas muscles.
• Nerve to sartorius m. exits and lies superficial
  and medial to main body of femoral n.

5

• Note fascias lata and iliaca. Fascia iliaca lies
  between the artery and the nerve thus they lie
  in different compartments.

6
(No Transcript)
7
Femoral Nerve Cutaneous Distribution

• The femoral nerve supplies the anterior thigh and
  part of the medial thigh, then as the saphenous
  nerve supplies the medial aspect of the lower leg
  and ankle.

8
Knee Hip Bone Innervation
Anterior
Posterior
9
Standard Femoral Block Technique

• Palpate femoral artery at inguinal crease.
• Mark a spot 1 cm lateral to pulse.
• Advance needle till quadriceps twitch obtained.

10
Issues With Standard Technique
Body Size
11
Sartorious Twitch
Issues With Standard Technique

• Injection should not be done when a sartorius
  twitch is present, because the nerve may have
  already exited the sheath.

12
Injection Outside Sheath
Issues With Standard Technique
13
Femoral N. Ultrasound Imaging (1)

• Positioning
• Patient flat, stomach retracted with wide tape
  if needed.
• Stand on side of block, machine on opposite side.
• Try to line up needle, transducer, and US monitor
  makes it easier to image your needle.

14
Femoral N. Ultrasound Imaging (2)

• Holding the Probe
• Notice the hand is holding the probe in a way
  that the side facing us is easily visualized
  making it easier to get the needle lined up with
  the middle of the probe.
• Notice that the hand is resting on the patients
  skin. This helps keep the probe from sliding
  around on the gel.

15

• SAX approach.

16
Imaging

• Start below crease.
• Perpendicular to leg, not parallel to crease.
• Look for femoral artery, white triangle.

Yes!
No!
17
The white triangle anatomic correlations
18
Example Images
19
Lateral
Medial
20
Lateral
Medial
Try to identify the fascial planes and the nerve.
21
Lateral
Medial
22
Lateral
Medial
23
Lateral
Medial
24
Fine Tuning Imaging

• Slight rotational and angle adjustments of probe,
  to get best cross section.
• Move probe cephalad to find best compromise
  between femoral nerve image and depth. (As you
  move cephalad, the nerve becomes a more distinct
  bundle. However, it can be harder to image as it
  gets deeper.)

25
Medial
Lateral
26
Medial
Lateral
Another example. Try to identify the fascial
planes and the nerve.
27
Medial
Lateral
28
Medial
Lateral
29
Medial
Lateral
30

• Note second artery below femoral artery the
  profunda femoris branch.

31

• At this location, femoral nerve is also branching
  out, and harder to image, so best to move more
  cephalad.

32
The probe is being moved cephalad.
33
Approaches With Stimulation
IP
OOP
34
OOP
IP
35
Approaches No Stimulation

• Here, an 18 g Touhy needle is being used easier
  to see with US, and easier to feel the 2 pops
  through fascias lata and iliaca.

36
Dont aim for nerve. Aim to pierce fascia iliaca
lateral to nerve. Feel fascial pop, then give 1
ml test dose to confirm location.
37
OOP Geometry
A good goal for the OOP approach would be that
your needle tip approaches the nerve at the point
that the ultrasound beam intersects with the
nerve. That way, you will be sure to see your
test injection. You can measure depth to nerve
with US, then use that information as shown.
38
Example of In Plane Approach
39
Example of Out of Plane Approach
Note that the needle isnt seen here, but tissue
movement shows general track of the needle.
40
Injection
41
More Injection
42
In Plane Outside Sheath
An example of a test injection above the fascia
iliaca, and probably also above the fascia lata.
43
Out of Plane Outside Sheath
An example of a test injection above the fascia
iliaca.
44
One more nice example a 16 y/o female for an ACL
repair.
45
Post injection. Even though nerve is not
completely surrounded with local, the block is
still usually good.
46
ScenarioTotal Knee Replacement

• Preop meds celexecob, gabapentin
• Spinal anesthesia
• Femoral single shot block vs catheter
• Pre or postop.
• Local by surgeon (helps with sciatic mediated
  pain).