Chapter 77 Blocks of the Lumbar Plexus and its Branches Flashcards Preview

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Flashcards in Chapter 77 Blocks of the Lumbar Plexus and its Branches Deck (91):
1

he roots of the lumbar
plexus

deeply located, coursing through the substance
of the psoas major muscle in their journey from the lumbar
paravertebral space to the lower extremity

2

The fasciae of the large psoas major muscle (anteriorly) and
quadratus lumborum muscle (posteriorly) invest the lumbar
plexus from its origin at the

anterior primary rami of
the L1, L2, L3, and L4 nerve roots

3

The proximal
part of the lumbar plexus supplies

the iliohypogastric and
ilioinguinal nerves, which are in series with the thoracic
nerves and innervate the lower trunk.

4

The iliohypogastric
nerve supplies

the skin of the buttock and the muscles of
the abdominal wall.

5

The ilioinguinal nerve supplies

the skin
of the perineum and adjoining inner thigh

6

The genitofemoral
nerve (from L1 and L2) supplies

the genital area
and adjacent thigh.

7

The three major components of the
lumbar plexus

(femoral, lateral femoral cutaneous, obturator nerves) soon divide and take widely divergent course down through the pelvis toward their ultimate destinations in the leg.

8

Of the three nerves, only the largest branch of the lumbar plexus, remains in close
proximity to the psoas muscle as it descends toward the leg

the femoral nerve

9

The lateral femoral cutaneous nerve leaves the lateral border of the

psoas major muscle at about its midpoint and
enters the lateral thigh at a very superficial level

10

The obturator
nerve leaves the medial border of the

psoas major muscle and enters the medial thigh at a deeper level, within the adductor muscle compartment.

11

The femoral nerve derives from the dorsal portions of

L2, L3, and L4,

12

femoral nerve course

descends from its origin to appear at the lateral margin of the psoas major at approximately the junction of the middle and lower thirds of that muscle. As the nerve continues on its descent toward the leg, it remains between the psoas major and the iliacus muscles so
that, proximal to the inguinal ligament, the femoral nerve is surrounded laterally by the iliacus fascia, medially by the fascia of the psoas major, and anteriorly by the transversalis fascia. Distal to the inguinal ligament, the fused iliopsoas fascia continues to provide a posterior and lateral wall to this compartment

13

The lumbar plexus
can also be blocked

using an anterior approach distal to the inguinal ligament (the inguinal paravascular technique) that attempts to block the three major nerves using a modification
of the standard femoral nerve block technique (3-in-1 block). The lumbar plexus
can also be blocked with a posterior approach or psoas
compartment block

14

LUMBAR PLEXUS BLOCK
INDICATIONS

Lumbar plexus block is indicated for surgeries of the thigh or knee, including above-the-knee amputation, as a diagnostic and therapeutic tool for chronic pain disorders, or to provide analgesia for painful conditions of the proximal
leg, including herpes zoster. It can also provide analgesia
following a variety of surgical procedures of the thigh or knee, including femoral shaft surgery, total knee and hip replacements, and open-reduction and internal fixation of
acetabular fractures.

15

LUMBAR PLEXUS BLOCK ADVANTAGES

reduce opioid
requirements as part of a multimodal analgesic regimen following total hip or knee arthroplasty. Blood loss following total hip arthroplasty is reduced using this
block when compared with general anesthesia

16

LPB Positioning

A posterior approach or psoas compartment block is typically
performed with the patient in the lateral decubitus position with the intended surgical site uppermost. The
upper thigh is flexed at the hip and the knee is flexed (i.e., Sim’s position).

17

LUMBAR PLEXUS BLOCK

LANDMARK

A line is drawn between the iliac crests (intercristal line) and another one is drawn through the
lumbar spinous processes. The posterior superior iliac
spine (PSIS) is identified and marked. A line is drawn, parallel
to that connecting the lumbar spinous processes from about L3 inferiorly, bisecting the PSIS. The site of needle insertion is where the parallel spinous line (or paraspinous line) bisects the intercristal line.

18

LUMBAR PLEXUS BLOCK

TECHNIQUE

a 4-inch, 22-gauge insulated regional block needle is advanced perpendicular
to all planes until the desired transverse process is encountered. The needle is then re-directed in a slightly cephalad direction and advanced slowly beyond the transverse process (not more than 2 cm after bony contact) until a quadriceps contraction is elicited, typically at a current of up to 0.5 mA. The usual volume of local anesthetic is 30 ml.

19

LUMBAR PLEXUS BLOCK

Complications

systemic local anesthetic toxicity
and retroperitoneal hematoma, unintended
epidural placement

20

The inguinal paravascular technique of lumbar plexus block (3-in-1 block)

With the patient in the supine position, the
lateral edge of the femoral arterial pulse is palpated about
1 to 2 cm distal to the inguinal ligament. A 22-gauge, 2-inch insulated regional block needle is advanced using
nerve stimulator guidance in a cephalad direction at about a 30º angle to the skin, with the needle entry point 1 cm lateral to the femoral artery. A quadriceps muscle response is sought at a current of up to 0.5 mA. Increasing the volume of LA from 20 to 40 ml (mepivacaine
1%) modestly increases the chances of blockade of the three nerves. Ropivacaine 0.25–0.5% and bupivacaine 0.25% provide similar degrees of analgesia following total knee replacement using a single-injection technique.

21

3-in-1 block indications

hip fracture
repair and knee arthroscopy

22

The major difference between 3-in-1 block and femoral nerve block

a larger volume of LA is used, providing a greater degree of muscle relaxation and a longer duration of postoperative analgesia

23

LUMBAR PLEXUS BLOCK

ULTRASOUND-GUIDED TECHNIQUE


Positioning

The patient is
positioned either in the sitting or lateral decubitus position
with the side to be blocked uppermost.

24

LUMBAR PLEXUS BLOCK

ULTRASOUND-GUIDED TECHNIQUE

Scanning

A lowfrequency
(4–5 MHz) curved array transducer ensures sufficient depth of imaging. An initial longitudinal paramedian scan allows precise identification of the intervertebral spaces. The probe is initially placed at the upper
end of the sacrum (seen as a continuous hyperechoic line),
just off the midline, in an oblique plane of imaging angulated
toward the midline, and slowly maneuvered in a
cephalad direction. The first “break” in this line represents the L5/S1 junction. The laminas of L5, L4, L3, and L2 are subsequently identified in a similar manner. The lower pole of the kidney can be found as caudally as L3/ L4 on deep inspiration. It is prudent, therefore, to continue to scan higher and laterally until the kidney is identified (hypoechoic oval-shaped structure) to avoid accidental
puncture. The probe is then positioned at the interspinous level where the block is to be placed and rotated 90° from a longitudinal to a transverse orientation

25

LPB
Important internal bony landmarks that
need to be identified include

the vertebral body, spinous process, articular process, and transverse process

26

LPB
Important soft tissue structures to be identified include

the erector spinae, quadratus lumborum, and psoas muscles. Deep (anterior) to the psoas muscle, the intraperitoneal
structures can be seen

27

targeted for LA injection

The roots that form the lumbar plexus are rarely imaged in adults but are known to run
through the posterior or middle third of the psoas muscle.

28

LUMBAR PLEXUS BLOCK US

Medial needle angulation is
best avoided to prevent

inadvertent subarachnoid injection

29

help locate the needle tip (the so-called hydrolocation technique).

Injecting 5% dextrose
(D5W) in 0.5 to 1 ml increments

30

LUMBAR PLEXUS BLOCK US

Needle technique

The needle should be advanced until its tip is positioned in the posterior third of the psoas muscle. A peripheral nerve stimulator can be used to confirm the position
by observing quadriceps contraction. After negative aspiration, the desired LA volume may be administered in divided doses and fluid and tissue expansion can be observed within the psoas muscle.

31

the lumbar plexus
may be successfully blocked using the “trident” acoustic
window

(the shadows of the transverse processes in the
longitudinal plane) as a landmark

32

Complications of continuous
techniques are similar to those occurring after single shot
blocks

femoral neuropathy and femoral nerve compression from a subfascial hematoma. Systemic toxic reactions to local anesthetic may also
occur from intravascular injection or from exceeding the
recommended local dosing limits. Arterial puncture and
intravascular catheter placement, although rare, do occur, as does epidural block from advancing the catheter too far in a cephalad direction

33

femoral nerve course

femoral nerve (L2–L4) courses from the lumbar plexus in the groove between the psoas major and iliacus muscles, where it enters the thigh by passing deep to the inguinal ligament. At the level of the groin crease, the femoral nerve lies anterior to the iliopsoas muscle and
slightly lateral to the femoral artery. At or above the inguinal ligament, the femoral nerve
divides into anterior and posterior divisions; Both divisions lie deep to the fascia iliaca.

34

femoral nerve innervations

the anterior division innervates the skin over the anterior thigh and supplies the sartorius muscle, and the posterior division innervates the quadriceps femoris muscle, the knee joint, and its medial ligament, and also is the division from which the saphenous nerve is derived. Therefore posterior division
block is essential for successful femoral nerve block
for procedures of the anterior thigh and knee. The two
divisions may lay one behind the other (as their names suggest, respectively), or side-by-side at the level of
the groin crease

35

Stimulation of the anterior division results in

muscle contraction of the medial thigh (sartorius twitch).

36

The branches from the anterior and posterior division are primarily

The branches from the anterior division are primarily sensory and the branches from the posterior division are primarily motor.

37

INDICATIONS Femoral nerve block

provide analgesia to a fractured
shaft of the femur following total knee arthroplasty and anterior cruciate ligament reconstruction, or for skin graft donor sites of the anterior thigh. It may also suffice for analgesia following quadriceps tendon repair and in hemiplegic patients for the reduction of quadriceps
spasticity. used in a
(PCA) mode for analgesia following total hip or knee
arthroplasty

38

FEMORAL NERVE BLOCK
SURFACE LANDMARK–BASED TECHNIQUES:

The patient lies supine with the leg on the operative side
extended. The needle entry site is marked using a felttipped marking pen, 1 cm lateral to the arterial pulsation
at the level of the inguinal crease. A 22-gauge, short beveled, 2-inch insulated regional block needle is advanced from the injection site in a cephalad direction at a 60° angle to the skin surface. A peripheral nerve stimulator is used to elicit the “patellar snap” (quadriceps femoris muscle contraction) at a stimulating current of up to 0.5 mA. Once a brisk patellar snap is observed, a volume of 20 to 25 ml of LA is incrementally injected. Bupivacaine or ropivacaine with epinephrine 1:200,000 are frequently used. Alternatively, for shorter-duration block, 1% to 1.5% lidocaine or mepivacaine with epinephrine may be employed

39

If a sartorius twitch is observed on the lower medial thigh,
the stimulating needle should be

advanced an additional
5 to 10 mm to stimulate the posterior division of the nerve

40

Successful Femoral Nerve block is indicated by

quadriceps muscle weakness, anterior thigh anesthesia, and
saphenous nerve sensory analgesia.

41

FEMORAL NERVE BLOCK
ULTRASOUND-GUIDED TECHNIQUE

The patient is positioned supine with the leg slightly abducted. A high frequency (10–15 MHz) linear array transducer is positioned over the inguinal crease, and the femoral artery and vein are identified superficial to the ilio-psoas muscle. If more than one artery is observed, a location distal to the femoral artery bifurcation is implied, and the probe should be moved in a cephalad direction until the arteries converge. The transducer is then moved laterally to locate the femoral nerve. The nerve is typically hyperechoic and located deep to the fascia iliaca (a continuous hyperechoic
line) but superficial to the iliopsoas muscle. A block needle is guided toward the lateral aspect of the nerve, where the posterior division of the nerve is often located. After negative aspiration, the
LA is injected in divided doses

42

The nerve can be distinguished from nearby
lymph nodes by

scanning in a proximal to distal direction. The nerve is a continuous structure, while lymph nodes are discrete

43

FEMORAL NERVE BLOCK

technique can be modified to allow for catheter placement

D5W may be used to expand the sheath compartment to facilitate catheter placement. An in-plane or out-of-plane approach may be used. Suggested methods to ease placement include keeping the needle tip slightly away from the target, turning the bevel to face in a cephalad direction, and caudal angulation of the needle hub. No more than 3 to 4 cm of catheter need to be passed through the end of the needle.

44

Complications associated with femoral nerve block

vascular puncture with hematoma formation,
intravascular injection, and femoral nerve palsy. vascular puncture with hematoma formation, intravascular injection, and femoral nerve but catheter-related infection is very rare palsy.

45

relative contraindication to femoral nerve block

A history of previous ilio-inguinal surgery, including
vascular grafting and resection of tumors or inguinal lymph nodes,

46

The lateral femoral cutaneous nerve (LFCN

a purely
sensory nerve that is derived from L2–L3 roots

47

course of lateral femoral cutaneous nerve

After emerging from the lateral border of the psoas major muscle, the LFCN lies deep to the fascia lata, and medial and
inferior to the anterior superior iliac spine (ASIS). The
LFCN enters the thigh below the inguinal ligament, medial
or lateral to the ASIS. There is a relatively consistent
relationship between the LFCN and the tendinous origin of the sartorius muscle

48

typically results in LFCN block

LA infiltration
anterior to the sartorius muscle, distal to the inguinal ligament

49

lateral femoral cutaneous nerve (LFCN) divides
into

anterior and posterior branches about 7 to 10 cm below the ASIS. The anterior branch supplies the skin over
the anterolateral aspect of the thigh as low as the knee, and
the posterior branch supplies the skin over the lateral aspect
of the thigh from just below the greater trochanter to
about the mid-thigh

50

LATERAL FEMORAL CUTANEOUS NERVE BLOCK
INDICATIONS

provide analgesia of a skin graft donor site on the lateral thigh, for performing muscle biopsies during work-up of malignant hyperthermia, or as a supplement to femoral and sciatic nerve blocks for lower
extremity surgery where a thigh tourniquet will be required.

51

LFCN block is an important aid in diagnosing

syndrome of meralgia paresthetica.

52

Lack of significant
pain relief in the presence of demonstrable analgesia in the
lateral thigh area following the block may indicate

a more proximal source of lateral thigh pain, including lumbar radiculopathy or intrapelvic pathology. meralgia paresthetica.???

53

Treatment of meralgia
paresthetica may include

repeated LFCN blocks using
combinations of local anesthetics and corticosteroids

54

LATERAL FEMORAL CUTANEOUS NERVE BLOCK

SURFACE LANDMARK AND TECHNIQUES

The sensory stimulation technique is performed with the patient in the supine position. The ASIS is marked using a felt-tipped marking pen. A point 2 cm medial and inferior to the ASIS is identified and also marked. A nerve
stimulator is set to deliver a 2 to 3 mA current using a
single-twitch cycle. The negative lead is moved from medial to lateral until a paresthesia is elicited corresponding to the
innervation of the lateral thigh in the distribution of the
posterior branch of the LFCN. An uninsulated 22-gauge, 2-inch regional block needle connected to the nerve stimulator is then introduced and the same paresthesia should be elicited at 0.5 to 0.6 mA at 1 Hz. A total volume of 5 to 8 ml of local anesthetic should be incrementally injected in divided doses.

55

LATERAL FEMORAL CUTANEOUS NERVE BLOCK

the blind infiltration technique

the ASIS is again marked. A second point, 2 cm medial and 2 cm caudad to the ASIS is also marked. A 22-gauge, 2-inch short beveled needle is advanced through a local anesthetic skin wheal at this second point in a direction
toward the ASIS (point one). As the needle traverses
the fascia lata, a distinct “pop” will be felt. Fifteen to 20 ml
of LA may be deposited in a fanwise manner, both above
and below the fascia lata, specifically between the fascia lata and the sartorius

56

LATERAL FEMORAL CUTANEOUS NERVE BLOCK

ULTRASOUND-GUIDED TECHNIQUE

With the patient in the supine position, a high-frequency
linear array transducer is positioned transversely, just inferior and medial to the ASIS. By moving the probe in a
caudad direction, the sartorius muscle is identified. This
muscle has a triangular shape and runs obliquely and medially as it descends in the thigh. Superficial to the sartorius, the fascia lata and the fascia iliaca can be identified. The LFCN is located between these two fascial planes, running in a lateral direction anterior to the sartorius muscle. It may appear as a discrete hyperechoic round, elliptical, or lip-shaped fibrillar structure. Paresthesia in the distribution of the LFCN can then be sought prior to LA injection. The block needle is inserted in-plane to the probe and
directed toward the nerve using a shallow angle. hydrodissection with D5W between the fascia
lata and fascia iliaca may enhance the visibility of the
LFCN

57

can occur
with landmark techniques when blocking the LFCN.

Inadvertent blockade of the femoral and obturator nerves

58

The obturator nerve

derived from L2–L4, although
the contribution from L2 is frequently small or even
nonexistent.

59

The obturator nerve course

The nerve emerges at the upper level of the medial border of the psoas major muscle at the approximate
level of the sacroiliac joint and passes behind the iliac vessels from which it is separated by the fascia iliaca. It continues its downward course with the iliac vessels and obturator artery and vein along the obturator groove and passes through the obturator foramen into the thigh. At the level of the obturator foramen or canal, the nerve divides into two terminal branches (anterior and posterior) that supply the medial thigh.

60

obturator nerve innervations

The anterior branch supplies an articular branch to the
hip joint and the anterior adductor muscles (pectineus,
adductor longus, adductor brevis), and makes a small
cutaneous contribution to the medial and inferior thigh.
The posterior branch innervates the deep adductor muscles (adductor brevis and magnus, obturator externus)
and frequently sends a contribution to the knee joint.
Some individuals may have a small accessory obturator nerve derived from the ventral rami of L3 and L4. This accessory branch may give off rami to the pectineus and
hip joint.

61

OBTURATOR NERVE BLOCK


INDICATIONS

indicated in the diagnosis and management of painful conditions of the hip and for the relief of adductor spasm of the hip. The block is also a valuable adjunct to femoral and lateral femoral cutaneous nerve blocks for surgeries of the knee, or for analgesia for
surgical tourniquets placed on the thigh.

62

Obturator nerve block used as an adjunct for

transurethral surgeries for bladder tumors, since
subarachnoid block or general anesthesia without the aid of
muscle relaxants does not routinely prevent adductor muscle contractions that could contribute to bladder perforation, bleeding, or incomplete resection.

63

OBTURATOR NERVE BLOCK

SURFACE LANDMARK AND TECHNIQUE

The patient is placed in the supine position with the leg
to be blocked slightly abducted. The pubic tubercle is palpated and a local anesthetic skin wheal is raised 1 to 2 cm below and 1 to 2 cm lateral to it. A short-beveled,
22-gauge, 3.5-inch needle is advanced through the skin
wheal in a slightly mesiad direction until the ramus of the
pubis is contacted. Once the horizontal ramus is identified,
typically at a depth of about 1.5 to 4 cm, the needle is
withdrawn and re-advanced in a cephalad direction to attempt
to enter the obturator canal. This should occur at a
depth about 2 to 3 cm deeper than that at which the ramus
was contacted. Once the canal has been contacted, the
needle must again be withdrawn and redirected slightly laterally and inferiorly until it enters the obturator canal. Once within the canal, the needle is advanced
2 to 3 cm, and after ascertaining via negative aspiration that the obturator vessels have not been punctured, 10 to 15 ml of local anesthetic are incrementally injected.

64

OBTURATOR NERVE BLOCK


It is essential to identify

the bony wall of the obturator canal to verify that the needle has not entered contiguous
structures such as the rectum or vagina, which lie medially and superiorly

65

OBTURATOR NERVE BLOCK


an alternative technique, using a peripheral
nerve stimulator

As an alternative technique, a peripheral nerve stimulator may be used to find the nerve. In this approach, the 22-gauge insulated regional block needle is advanced until adduction of the thigh is noted at stimulating currents of less than 0.5 mA. Successful block is heralded by the onset of weakness of thigh adduction

66

OBTURATOR NERVE BLOCK


ULTRASOUND-GUIDED TECHNIQUE

a high-frequency linear-array transducer is placed in the inguinal crease and the femoral vessels are identified. Medial to the vessels lies the pectineus muscle. More medially the three adductor muscles can be observed—adductor longus (the most superficial), adductor brevis, and adductor magnus (the deepest). At this location the nerve has most likely divided into its anterior and posterior branches. These branches are
small in size (2–3 mm in diameter) and are found within the fascial planes investing adductor brevis. (The anterior division lies between adductor longus and adductor brevis; the
posterior branch between adductor brevis and adductor
magnus.). The nerves usually
appear as fascicular structures, flat or lip-shaped with discrete hypoechoic internal areas. The block needle is advanced, aiming to target both branches

67

Potential side effects and
complications of obturator block include

intravascular injection,
nerve injury with resultant neurapraxia or neurotmesis,
and the aforementioned injection into contiguous,
unintentional sites such as the rectum or vagina. Obturator
arterial injury has also been reported in a patient undergoing resection of a bladder tumor

68

saphenous nerve

the only cutaneous branch of the posterior division of the femoral nerve

69

saphenous nerve course

It arises in the femoral triangle, descends lateral to the femoral artery, and then enters the adductor canal of Hunter, where it crosses over the artery to lie in an anteromedial position.

70

The
saphenous nerve supplies

an extensive cutaneous area over the medial side of the knee, leg, ankle, and foot. The nerve exits the lower part of the canal by emerging between the sartorius and gracilis muscles. At this level this small nerve becomes superficial (subcutaneous), and it soon divides into two branches: the infrapatellar branch innervates a small
cutaneous area distal to the knee, and the sartorial branch
runs down the medial aspect of the leg, innervating this
area all the way to the ankle and sometimes the medial aspect of the foot.

71

SAPHENOUS NERVE BLOCK

INDICATIONS

in conjunction with
sciatic nerve block to provide complete anesthesia or analgesia to the ankle and as a component of ankle block for
foot surgery. Chronic pain applications include blocks for
saphenous neuralgia or saphenous nerve entrapment at the adductor canal

72

SAPHENOUS NERVE BLOCK
Locations

The saphenous nerve can be blocked above the knee,
at the level of the knee, below the knee, and just above the medial malleolus.

73

SAPHENOUS NERVE BLOCK

Blockade above the knee includes

the
perifemoral, subsartorial, and transsartorial approaches

74

SAPHENOUS NERVE BLOCK

Blockade at the level of the knee includes

includes the paracondylar
saphenous field block (PSFB) and the nerve stimulator technique, where the nerve is blocked at the level of the medial femoral condyle

75

The saphenous nerve
has also been blocked by subcutaneous infiltration below

the knee distal to the medial condyle of the tibia (belowthe-
knee field block [BKFB]) and the paravenous approach. Finally, the saphenous nerve can be blocked just above the medial malleolus of the foot

76

SAPHENOUS NERVE BLOCK


PERIFEMORAL APPROACH

The site of needle insertion is 5 to 6 cm distal to the inguinal
crease, 0.5 cm lateral to the femoral artery. At 2 to
4 cm depth, the nerve to the vastus medialis muscle is
stimulated, resulting in the contraction of the medial aspect of the thigh. The vastus medialis muscle contracts secondary to stimulation of the nerve to the vastus medialis muscle, which runs alongside the saphenous nerve. The nerve to the vastus medialis muscle is used as a landmark to locate the saphenous nerve since the saphenous nerve is purely a sensory nerve

77

SAPHENOUS NERVE BLOCK


TRANSSARTORIAL APPROACH

The sartorius muscle is identified; this is facilitated in the supine patient who elevates the extended leg. The site of needle insertion is 3 to 4 cm superior and 6 to 8 cm posterior to the superomedial border of the patella. The insulated needle is inserted at an angle of 45° caudally and directed
slightly posteriorly. Paresthesia may be elicited with a nerve stimulator at 3 to 5 cm depth

78

SAPHENOUS NERVE BLOCK


BELOW THE KNEE FIELD BLOCK

A linear subcutaneous injection of local anesthetic is made immediately below the insertion of the sartorius tendon at the tibial tubercle. The infiltration is made in an
anterior and posterior direction up to the anteromedial
aspect of the gastrocnemius muscle.

79

SAPHENOUS NERVE BLOCK


BELOW THE KNEE FIELD BLOCK

paravenous approach

wherein the saphenous vein is identified in the medial head of the gastrocnemius muscle at the level of the tibial tubercle. Subcutaneous infiltration is made lateral and medial to the saphenous vein. In this technique the patient’s leg hangs down and a tourniquet is used to make the saphenous vein prominent

80

SAPHENOUS NERVE BLOCK


BLOCKADE AT THE MEDIAL MALLEOLUS

Local anesthetic is injected subcutaneously above the
medial malleolus of the foot. The injection extended
anteriorly and posteriorly above the medial malleolus

81

ultrasound-guided technique at the distal adductor canal

landmark

the saphenous branch of the
descending genicular artery (SBDGA) as a landmark

82

SAPHENOUS NERVE BLOCK


ULTRASOUND-GUIDED TECHNIQUE

At the level of the adductor canal the saphenous nerve lies in close proximity to the femoral artery, immediately deep to the sartorius muscle. The patient is supine with the leg abducted and slightly externally rotated. A high frequency linear array transducer is placed on the medial aspect of the distal thigh perpendicular to the
long axis of the leg. Sartorius, vastus medialis, and the femoral artery are identified. In this area, the nerve is located antero-medial to the artery, deep to the sartorius muscle and medial to the vastus medialis. It appears as a small, hyperechoic structure with a honeycomb internal appearance. The structure is confirmed to be neural
by tracing its course as far as the adductor hiatus. Successful
blockade can occur within the adductor canal (approximately
10–13 cm proximal to the knee crease) using the femoral artery as the landmark.

83

A potential downside of blocking the saphenous nerve at the adductor canal is

concurrent blockade of some of the most distal branches of the motor nerve to the vastus medialis, which also accompanies the femoral artery in this region. However, this will not result in complete quadriceps weakness, only partial weakness of the vastus medialis.

84

SAPHENOUS NERVE BLOCK


An alternative approach

to block the nerve more
distally after it leaves the adductor canal by piercing the fascial plane between the sartorius and gracilis muscles, using the saphenous branch of the descending genicular artery (SBDGA) as a landmark. If the nerve cannot be seen, LA may be deposited
under the sartorius, close to this artery.

85

SAPHENOUS NERVE BLOCK


Below the knee,

the nerve is difficult to visualize. Its anatomic relationship to the saphenous vein in the proximal leg provides a substitute landmark (the nerve is adjacent to the vein).

86

The femoral nerve, LFCN, and obturator nerve run a considerable part of their course close to

the inner aspect of the fascia iliaca.

87

The fascia iliaca

attached medially to the
vertebral column and upper part of the sacrum. It covers the
psoas muscle and iliacus muscle and is attached to the inner lip of the iliac crest and pelvic brim. At the groin the fascia iliaca is continuous with the posterior margin of the inguinal ligament. Laterally it attaches to the ASIS. Medially it
blends with the pectineal fascia. The fascia iliaca reflection thus forms a triangular potential space, the “fascia iliaca
compartment.” Distally, at the level of the femoral triangle,
the fascia iliaca becomes narrow. It is covered by the fascia lata and forms the roof of an adipose-filled space known as the lacuna musculorum, which lies adjacent to the femoral vessels.

88

injection of a sufficient volume
of local anesthetic solution into the lacuna musculorum
favors

cephalad migration toward the iliacus muscle, facilitating
spread of LA within the entire fascia iliaca compartment
and resulting in blockade of all three component nerves (femoral, obturator, LFCN) that lie within it.

89

FASCIA ILIACA BLOCK


INDICATIONS

used in the prehospital treatment of femoral fractures. It can provide analgesia following total knee replacement surgery and a variety of other proximal surgeries of the lower extremity

90

FASCIA ILIACA BLOCK



SURFACE LANDMARK–BASED TECHNIQUE

With the patient in the supine position, a line is identified
from the anterior superior iliac spine to the pubic tubercle. The needle entry site is 1 cm distal to the point where the middle and lateral thirds of the inguinal line meet. A 22-gauge short-beveled regional block needle is inserted at the marked site and advanced in a cephalad direction at a 75° angle to the skin. Alternatively, a 20-gauge Tuohy-type needle may be substituted. The “loss of resistance” (tissue “pop”) will be appreciated as the needle tip traverses the fascia lata. The needle continues to be advanced, however,
until a second loss of resistance is experienced. This second loss of resistance corresponds to the needle entering and passing through the fascia iliaca. The 75° angle of the needle to the skin is then reduced to about 30° and the needle is advanced an additional 1 cm in a cephalad direction.
After negative aspiration tests, a volume of local anesthetic (25 to 30 ml) is incrementally injected in divided doses.

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FASCIA ILIACA BLOCK

ULTRASOUND-GUIDED TECHNIQUE

A high-frequency linear-array
transducer is placed transversely over the area of the inguinal ligament. Two fascial planes (fascia lata and the deeper fascia iliaca) will be observed. They appear as two distinct continuous hyperechoic lines. A block needle is inserted in-plane to the probe. The needle tip should lie just below and deeper to the fascia iliaca. After negative aspiration,
the desired LA is then injected in divided doses. LA should
be noted to spread both in a medial and lateral direction
under the fascia iliaca.

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