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EDRA > 5.2 Lower Limb > Flashcards

5.2 Lower Limb Flashcards

1
Q

LumboSacral plexus

A

The lumbosacral plexus
is not a single plexus;

it comprises two distinct
and separate components:

the lumbar and sacral plexus.

A single injection of the lumbosacral
plexus cannot anaesthetise the whole lower extremity.

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2
Q

The lumbar plexus is derived from

A

The lumbar plexus is derived from the anterior primary rami (ventral) T12–L4,

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3
Q

The sacral plexus is derived from

A

The sacral plexus is derived from anterior primary rami

(ventral) L4–S3 spinal nerves

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4
Q

What is the benefit of LL block vs central

A

The renewed popularity of lower-limb peripheral blocks has been
attributed to techniques such as ultrasound guidance and continuous catheter techniques.

It also avoids the potential risk of epidural
haematoma in orthopaedic patients, where the use of venous
thromboprophylaxis is routine

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5
Q

Is lumbrosacral plexus block effective

A

Continuous lumbosacral plexus block
has been shown to be superior
to morphine patient-controlled analgesia
and equally effective as
epidural analgesia, for post-operative analgesia

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6
Q

facet joint pain.

A

the posterior (dorsal)
primary rami produce
lateral and medial branches
which innervate the back.

The medial branch innervates the
facet joint and is often targeted
as a chronic pain procedure to treat facet joint pain.

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7
Q

The lumbar plexus is

main supply

lies in

A

formed by the anterior primary rami of T12–L4

The lumbar plexus mainly supplies the anterior part of the thigh.

lie with the bulk of the psoas muscle

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8
Q

The lumbar plexus is most important branches:

A

most important branches:

1
the lateral cutaneous nerve of the thigh (LCN)
(lieslaterally),

2
the femoral nerve (FN)
(lies in between) and

3
the obturator nerve
(ON) (lies medially)

within the psoas muscle

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9
Q

Issue with FIB

A

evidence that the
LCN and the FN may
be separated from the
ON by a muscular compartment,

hence a fascia iliaca
or femoral three-in-one
block usually spares the obturator nerve.

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10
Q

The branches of the lumbar plexus (T12–L4)

A

Iliohypogastric

Ilioinguinal

Genitofemoral

LCN

Femoral
Obturator

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11
Q

Iliohypogastric

A 
Iliohypogastric
T12–L1
(anterior
rami)
Abdominal
muscles
Inferior abdomen and buttock
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12
Q

Ilioinguinal

A 
Ilioinguinal L1
(anterior
rami)
Abdominal
muscles
Medial thigh, external genitalia
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13
Q

Genitofemoral

A

Genitofemoral

L1–L2
(anterior rami)

Cremaster

Medial thigh, external genitalia

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14
Q

LCN

A

LCN

L2–L3
(posterior rami)

None

Lateral thigh

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15
Q

Femoral

A

Femoral

L2–L4
(posterior rami)

Anterior thigh muscles

Anterior thigh and medial side of l
eg below knee up to
medial malleolus

Hip and knee joint

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16
Q

Obturator

A

Obturator

L2–L4
(anterior rami)

Medial thigh muscle

Medial side of thigh,
posterior lower thigh

Hip and knee joint

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17
Q

Femoral nerve innervates

A

femoral nerve innervates

iliacus,

psoas,

sartorius,

quadriceps
(rectus femoris and three vastus muscles),

and pectinius.

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18
Q

The obturator nerve

motor

A

The obturator nerve

innervates three adductor muscles, 
obturator externus, 
gracilis 
and 
pectinius
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19
Q

Lateral cutaneous nerve of the thigh has

A

Lateral cutaneous nerve of the thigh has a

cutaneous innervation only.

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20
Q

What supply hips

knee

A 
The anterior divisions of both 
femoral and obturator nerve supply 
the hip joint, 
while their posterior branches 
supply the knee joint.
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21
Q

Hip surgery

A

Lower-limb blocks are an efficacious way to provide post-operative
analgesia.

lumbar plexus supplies the hip joint and part of the knee joint

Hence a lumbar plexus block offers good analgesia for hip surgery,
while femoral nerve block often proves inadequate for knee surgery

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22
Q

Knee replacement

A

sacral plexus supplies the posterior part of knee joint and ankle
as well. Hence a combined lumbar plexus–sciatic nerve block is
appropriate for a total knee replacement.

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23
Q

Ankle surgery

A

Only the medial malleolus of the ankle is supplied by the femoral nerve (via
the saphenous nerve), while the remainder is innervated by the sciatic nerve.

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24
Q

Dermatomes of lower limbs

T12-S5

A

T12 At inguinal ligament
L1 Pubic area
L2 Anterior medial thigh
L3 At the medial epicondyle of the femur
L4 Over the medial malleolus
L5 On the dorsum of the foot
S1 On the lateral aspect of the calcaneus
S2 At the midpoint of the popliteal fossa
S3 Over the tuberosity of the ischium or infragluteal fold
S4, S5 Perianal area

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25
Q

lumbar plexus block is performed at

A

L3–L5 level where the
lumbar plexus originates.

The aim is to block the 
three main branches by depositing 
a large volume of 
local anaesthetic within the 
bulk of psoas muscle
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26
Q

lumbar plexus block aim

A 
The aim is to block the 
three main branches by depositing 
a large volume of 
local anaesthetic within the 
bulk of psoas muscle
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27
Q

lumbar plexus block - needle passes

A

The needle pierces skin, subcutaneous fat, erector spinae, quadratus
lumborum and psoas major muscles.

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28
Q

Lumbar plexus block - landarks

A

The landmarks include

Posterior superior iliac spine
Iliac crest
Spinous processes of lumbar vertebrae

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29
Q

Lumbar plexus block - landmark lines (detail)

A

Line 1 –
iliac crest and intercristal line/Tuffier’s line (vertical).

Line 2 –
passing through spinous process of L4 and L5 (horizontal).

Line 3 –
parallel to the above line passing through the posterior
superior iliac spine (PSIS) (horizontal)

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30
Q

Various puncture points for lumbar plexus block (detail)

A

Puncture point:

Winnie’s: junction of lines 1 and 3. Anatomical studies suggest that
the location of this classic site is in fact too lateral.

Capdevila’s: the part of the intercristal line between lines 2 and 3 is
divided into three parts. The puncture point is the junction between
lateral and the middle third (as shown).

Chayen’s: caudal to Capdevila’s puncture point at L5 level

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31
Q

Performing lumbar plexus block:

Position

Needle

A

The patient in placed in the

lateral position
(side to be blocked uppermost)

and hips and knees flexed at right angles.

A 100–150-mm 22-G needle is inserted perpendicular to the skin at Capdevila’s puncture point.

The PNS is set at 1–2 mA #
and 100 μsec
pulse width.

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32
Q

Needle contact TV process how deep

Then how do you proceed

What is the response

A

The needle contacts the transverse process at 6–8 cm depth (varies with gender and body mass index).

This depth is noted and the needle
is withdrawn and reinserted by directing it
5° cranially or caudally,

to pass its tip beyond the transverse process 
until evoked motor response (EMR) for 
lumbar plexus (patellar twitch) is obtained.
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33
Q

How much further beyond TV process

A

The needle should

not be advanced more than 2 cm

beyond the transverse process,
as studies indicate the average distance

between transverse process and plexus
is 18 mm regardless of
body mass index
or gender.

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34
Q

What is a successful LP block

A

A successful lumbar plexus block

will anaesthetise the

FN, LFN and ON, and
the lower abdominal nerves

(iliohypogastric/ilioinguinal) in
70% of cases

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35
Q

Troubleshooting manoeuvres while performing a lumbar plexus block

Twitch of erector
spinae

A

Twitch of erector
spinae
Superficial muscles Advance needle deeper

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36
Q

Troubleshooting manoeuvres while performing a lumbar plexus block

Needle contacts
transverse process

A

Needle contacts transverse process

An important landmark that serves as a
guide; mark this distance

Redirect 5° cranially/caudally
to proceed deeper

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37
Q

Troubleshooting manoeuvres while performing a lumbar plexus block

Quadriceps twitch

A

Quadriceps twitch

(patellar tap)

Appropriate twitch Inject solution in aliquots of
5 mL

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38
Q

Troubleshooting manoeuvres while performing a lumbar plexus block

Obturator twitch

A

Obturator twitch

(thigh adduction)

Needle too medial

Redirect laterally at the same
level

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39
Q

Troubleshooting manoeuvres while performing a lumbar plexus block

Hamstring twitch

A

Hamstring twitch

Sacral plexus stimulation caudally or
medially (lumbosacral twig)

Redirect needle cranially and
laterally

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40
Q

Troubleshooting manoeuvres while performing a lumbar plexus block

Psoas twitch

A

Psoas twitch
(thigh flexion)

Needle is too deep and
is stimulating muscle
directly

Withdraw needle

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41
Q

Precautions while performing lumbar plexus block

Anticoag?

Needle Depth + Direction

A

1
The patient should not be anticoagulated, since this is a deep block.

2

The needle should not be advanced 2–3 cm beyond the transverse process.

3
The needle should not be directed medially to avoid epidural or intrathecal injection.

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42
Q

Precautions while performing lumbar plexus block

is there much blood supply?

A

4
Rapid, forceful injections must be avoided,
as this is a vascular area.

5
For the same reason, epinephrine should be added to injectate to permit early recognition of intravascular injections.

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43
Q

Precautions while performing lumbar plexus block

Motor response should be >?

Catheter?

A

6
Avoid injection of local anaesthetic when a response is produced with a current < 0.5 mA, as this may lead to epidural or intrathecal spread.

7
A continuous catheter should not be threaded beyond 3 cm, as it may migrate away from the plexus.

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44
Q

complications of the lumbar plexus block

common

A

complications of the lumbar plexus block
include

1
renal and

2retroperitoneal haematomas,

3
intravascular injections
(due to vascularity of this region),

4
nerve damage and

5
catheter placement in
the abdomen or other unintended places.

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45
Q

More serious complications of the lumbar plexus block include

A

More serious complications include
unintended sympathetic block
(spread to sympathetic chain located anteriorly),
epidural
(15%–30% incidence due to medial injections
or lateral extension of dural sleeves)
or even intrathecal anaesthesia.

In fact, the epidural spread may even
be bilateral.

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46
Q

Femoral nerve is formed by

A

FN is formed by the
posterior divisions
of the anterior rami of
the L2–L4 spinal nerves

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47
Q

Path of FN

A

first lies within the bulk of psoas muscle,

emerging from its lateral border
in a fascial compartment
between the psoas and iliacus muscles
and innervating both.

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48
Q

Path of FN regards inguinal

Relations to vascular

fascial relations

A

It then enters the thigh under the
inguinal ligament.

Here it lies lateral to femoral artery.

The femoral sheath contains the
femoral artery and vein,

which lie beneath the fascia lata but
above the fascia iliaca.

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49
Q

The femoral nerve lies deep to

A 
The femoral nerve lies deep to the 
fascia iliaca, 
which forms the iliopectineal ligament 
to separate the femoral nerve from the
femoral vessels medially
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50
Q

FN anterior division

A

The anterior division of the femoral nerve

supplies the skin of the
medial and anterior surfaces
of the thigh,

innervates sartorius

and pectineus muscles

and
provides articular branches to the hip.

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51
Q

FN Posterior division

A

posterior division of the

femoral nerve provides

muscular branches
to the quadriceps
and articular branches to the knee;

eventually it becomes the saphenous nerve.

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52
Q

The saphenous nerve lies

A

within the adductor canal
under the sartorius muscle
above the medial
aspect of the knee.

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53
Q

Various techniques to block femoral nerve

Peripheral nerve stimulator guided

A

Peripheral nerve stimulator guided femoral
nerve block

Inguinal crease,
1–2 cm lateral
to femoral artery

A 50-mm 22-G needle
is inserted at this
puncture point
directed 60° cephalad

Patellar twitch;
15–20 mL local anaesthetic is injected

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54
Q

Various techniques to block femoral nerve

Femoral three in-one block

A

Femoral threein-
one block

Inguinal crease,
1–2 cm lateral
to femoral artery

A 50-mm 22-G needle
is inserted at this
puncture point
directed 60° cephalad

Patellar twitch;
15–20 mL local anaesthetic is injected

Same as above Same as above Patellar twitch; higher
volume and distal
pressure applied

femoral three-in-one block does not consistently block obturator nerve

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55
Q

Various techniques to block femoral nerve

Fascia iliaca block

A

Fascia iliaca block

Line joining
anterior superior iliac spine
and pubic tubercle (inguinal ligament)

is divided into three parts

Needle inserted 1 cm
below the junction of
lateral and middle third

20 mL local anaesthetic
injected after two pops
(signifying fascia lata and fascia iliaca)

56
Q

Various techniques to block femoral nerve

Ultrasound
guidance

A

Ultrasound guidance

Inguinal crease Identifying
femoral vessels,
nerve and
fascia iliaca

Patellar twitch if a nerve
stimulator is used

Ultrasound guidance may reduce the volume of local anaesthetic needed and
the onset time of anaesthesia for femoral block, but no study has
demonstrated a reduction in peripheral nerve injury.

57
Q

Indications for femoral nerve block include:

Single injections:

A

Indications for femoral nerve block include:

Single injections: 
quadriceps biopsy, 
long saphenous vein stripping,
knee arthroscopy 
(along with intra-articular LA), 
analgesia for primary total knee replacement (TKR)
 and analgesia for anterior cruciate
ligament (ACL) reconstruction.
58
Q

Indications for femoral nerve block include:

Continuous catheter:

Combined with sciatic block:

A

Continuous catheter:
analgesia for
femoral shaft/femoral neck fractures

(catheter placed upon initial presentation) and TKR.

Combined with sciatic block:
any surgery below mid-thigh level

59
Q

Salient features of PNS-guided femoral nerve block are as follows.

performed where

A

Ideally performed at the inguinal crease, since:

1
The femoral nerve is widest and most superficial.

2
At inguinal ligament, needle directed cephalad can enter pelvis.

3
It is less painful than piercing through the inguinal ligament.

60
Q

Salient features of PNS-guided femoral nerve block are as follows.

Twitches

initial

final

redirection

A

Initially,
a sartorial twitch is obtained
(movement of lower medial thigh)
due to stimulation of anterior branch of femoral nerve.

The needle is then redirected
slightly deeper
(and laterally or medially) to

stimulate posterior branch
(supplying quadriceps),

resulting in typical ‘patellar twitch’.

Local anaesthetic (15–20 mL)
may be injected at this point
61
Q

Femoral N catheter

A

Femoral nerve catheters should
not be passed more than 3–5 cm beyond the tip,

as the chances of migration away from the nerve are
increased (i.e. medial or lateral rather than proximal

62
Q

Fascia iliaca block

How

A

It is the simplest way to block the femoral nerve.

A line joining
ASIS and pubic tubercle
(inguinal ligament)

is divided into three parts;
at 1 cm below the junction of the lateral and middle
thirds,
a 50-mm blunt-tipped needle is inserted angled at 60° cephalad

Two clicks or pops are detected as the needle pierces through the
fascia lata and the fascia iliaca, and 20–30 mL local anaesthetic is
injected

63
Q

Femoral three-in-one block:

detailed

A

Uses the same landmarks and technique as PNS-guided femoral nerve block,

but a larger volume of local anaesthetic 
and distal pressure is
used to encourage proximal migration 
block of the three main nerves
of the lumbar plexus.

However, studies have shown that this does not
occur and local anaesthetic actually spreads laterally and medially rather than proximally.

The following nerves are inconsistently anaesthetised during a three-in one block:

the LCN of the thigh,
the FN and the
anterior branch of the ON.

64
Q

Is 3 in 1 fem nerve suitable for inguinal or popliteal surgery

why

A

However,

the posterior branch
ON and

femoral branch of
genitofemoral nerve are

not blocked and it is unsuitable for surgery

performed in the inguinal or popliteal areas.

Also, because of
inconsistent block of anterior branch of the ON, surgery of medial
aspect of the thigh may also need supplementation in some form

65
Q

Continuous catheters FN

how

where in reation to fascia

A

Continuous catheters:
They may be inserted either using the
PNS or ultrasound.

The femoral nerve lies
deep to fascia iliaca,

and therefore the catheter tip
should lie below this layer.

66
Q

Continuous catheters FN

What axis of insertion

stimulating cateter better?

A

Catheters may be

inserted along the long axis (using the out-of-plane
approach) or

perpendicular to the long axis of the nerve (using the
in-plane approach).

Catheters may be non-stimulating or stimulating.

Theoretically, stimulating catheters should improve secondary block success rate;
however, recent reviews have only been able to demonstrate a limited benefit.

67
Q

The saphenous nerve

branch of

supplies

A

The saphenous nerve is the
terminal branch of the
posterior division
of femoral nerve.

It has no motor supply
and provides sensory innervations
to the

anterior thigh,
medial aspect of knee
and
leg down to the medial malleolus.

68
Q

The saphenous nerve

may be blocked in the following locations

A

may be blocked in the following locations

Above the knee:

subcutaneous infiltration above knee
subsartorial injection 5 cm above knee – blind or PNS/ultrasound guided.

Below the knee:

subcutaneous infiltration along the medial tibia and the media popliteal fossa;
paravenous technique (along the long saphenous vein) just distal to knee;
infiltration above medial malleolus.
69
Q

The saphenous nerve

Highest success

A

The highest success rate is achieved by
sub-sartorial injections.

The patient is positioned supine,

with the chosen leg slightly abducted and external
rotated.

The sartorius muscle is identified (above the medial aspect of the
knee) by asking the patient to elevate the leg slightly.

A 50-mm 22-G needle is inserted through the belly of sartorius to enter the subsartorial plane, and
paraesthesia is elicited in the saphenous distribution.

Local anaesthetic (10 mL) may be injected here. Using utrasound guidance, the saphenous nerve
may be identified in the subsartorial plane, sandwiched between the sartorius
and the vastus medialis initially and the sartorius and the gracilis distally.

Distally it lies next to the descending genicular artery, which serves as a
landmark for identification under ultrasound

70
Q

The obturator nerve originates

A

The obturator nerve originates

from
ventral (anterior) divisions
of anterior primary rami of
L2–L4 spinal nerve roots.

71
Q

The obturator nerve runs in

emerges at

A

It is formed within
the substance of psoas muscle and travels near its medial border, emerging
from the obturator foramen to enter the thigh.

72
Q

The obturator nerve
anterior division

runs

supplies

cutaneous?

A

Here it divides into an anterior division,
which lies between the

adductor longus
and pectinius above

and

the adductor brevis below.
ANTERIOR

It supplies these muscles

and gracilis,

articular branch to hip
and a variable

cutaneous branch to the
medial side of the thigh.

73
Q

The obturator nerve

Posterior division

A

The posterior division passes

deep or POSTERIOR to adductor brevis

but lies above adductor magnus.

It supplies adductor magnus
and
obturator externus;

and an articular branch to the knee joint.

pg 189

74
Q

ON variations

A

an accessory obturator nerve (L3, L4) may occur in a third of
individuals, and innervates the pectinius muscle.

75
Q

Various techniques for blocking the obturator nerve:

Winnie’s classic approach

A

Winnie’s classic approach:

2 cm lateral and
2 cm caudal to pubic tubercle,

a stimulating needle is inserted
perpendicular to the skin to
contact the pubic ramus.

Then it is walked off the
inferior edge of ramus to
enter the obturator foramen
until an adductor EMR is observed.

This approach is painful because of periosteal contact

76
Q

Winnie’s classic approach mcq thing for obturator

A

painful

77
Q

Inguinal approach
Various techniques for blocking the obturator nerve:

detailed

A

Inguinal approach:

a line is drawn from the femoral artery
to the medial border of adductor longus
on the inguinal crease.

At the midpoint of this line, 
a needle is inserted 30° cephalad 
in a parasagittal
plane to elicit a 
medial adductor response

(stimulation of adductor longus supplied by anterior branch of the ON) at a depth of about 4
cm, and 5 mL of local anaesthetic is deposited here.
The needle is redirected caudal and lateral towards adductor magnus to elicit a
posterior adductor twitch (stimulating posterior branch of ON) and a further 5 mL of local anaesthetic is injected.

78
Q

success of obturator block is assessed

A

success of obturator block is assessed

by loss of motor block only,

since the anterior branch inconsistently
supplies the medial thigh.

In addition, adductor magnus is also innervated by the sciatic nerve; therefore, it is not
completely paralysed with an isolated ON block.

79
Q

Ultrasound guidance approach: Obturator - benefit

A

helps to block both branches of ON

Ultrasound guidance approach: a high-frequency ultrasound probe is
placed parallel to the inguinal crease. The anterior branch is identified
between the adductor longus and the brevis, while the posterior branch
can be seen lying between the adductor brevis and the magnus
muscles.

80
Q

The LCN of the thigh derived from

originates
in

A

The LCN of the thigh is derived from
the dorsal division of anterior
rami of L2–L3.

It originates within the
body of psoas and emerges
from the lateral border of the
muscle to lie on the iliacus muscle.

81
Q

Where can the lateral cutaneous nerve be blocked

How

Related to lata and iliaca

A

The nerve proceeds towards the ASIS,
passing under the inguinal
ligament medial to the ASIS.

The LCN of the thigh may be blocked
here by injecting local anaesthetic
2 cm medial and 2 cm caudal to ASIS.

It lies under the fascia lata, but above the fascia iliaca.

82
Q

The sacral plexus is derived from

A

Lumbosacral trunk
(anterior rami of L4, L5)

and

the sacral nerves (anterior rami of S1–S3).

83
Q

The sacral plexus is formed

bounded by

A

It is formed within the pelvis
and exits it through the greater sciatic foramen

It is
bounded by piriformis posteriorly
and the iliac vessels anteriorly.

84
Q

What is terminal branches of sacral plexus

A

sciatic nerve is the
main terminal branch of the sacral plexus

(the other being the posterior cutaneous femoral nerve (PCFN)).

It is the largest
(2 cm wide)
and
longest nerve of the body (approx 45 cm till division).

85
Q

Branches of sacral plexus

Gluteal nerves

A

Gluteal nerves (L4–S2)

Superior gluteal nerve:
gluteus medius and minimus

Inferior gluteal nerve:
gluteus
maximus

Nerve to quadratus femoris

Nerves to the piriformis and
obturator internus muscles

Cutaneous
Upper medial buttock

86
Q

Branches of sacral plexus

Sciatic nerve

A

Sciatic nerve (L4–S3)

Common peroneal

tibial

87
Q

Branches of sacral plexus

A

Gluteal nerves

Sciatic nerve

Posterior femoral
cutaneous nerve

Pudendal nerve

88
Q

Branches of sacral plexus

PFCN

A

Posterior femoral cutaneous nerve
(S1– S3)

No motor

Inferior cluneal nerves and perineal branches:
lower medial buttock and posterior thigh

89
Q

Pudendal nerve

A

Pudendal nerve
(S2, S3, S4)

Muscles of the pelvic structures

External genitalia

90
Q

Sciatic nerve course and branches and relevant blocks

A

Mansour’s parasacral block
(lateral)
Labat’s classic sciatic nerve block
(lateral decubitus)

Subgluteal approach (lateral
decubitus)
Raj’s approach (lithotomy)

Beck’s anterior approach
(supine)

Sukhani’s infragluteal approach
(prone)

Guardini’s subtrochanteric block
(supine)

Popliteal block
(prone/supine/lateral/lithotomy

91
Q

Mansour’s parasacral block
(lateral)
Labat’s classic sciatic nerve block
(lateral decubitus)

A

Sciatic nerve exits the greater sciatic foramen, deep to the

piriformis

92
Q

Subgluteal approach (lateral
decubitus)
Raj’s approach (lithotomy)

A

Enters the thigh midway between the greater trochanter and the
ischial tuberosity

93
Q

Beck’s anterior approach

supine

A

Passes medial to the lesser trochanter

94
Q

Sukhani’s infragluteal approach

prone

A

Upper thigh: lies lateral to the tendon of biceps femoris

95
Q

Guardini’s subtrochanteric block

supine

A

Mid-thigh: under the belly of biceps femoris

96
Q

Popliteal block

(prone/supine/lateral/lithotomy

A

Popliteal fossa:
divides into a medial tibial nerve and lateral
common peroneal nerve (fibular nerve); bounded by biceps
femoris laterally, and semitendinosus and semimembranosus
medially

tibial and common peroneal nerves are two distinct nerves from the
very start contained within the same common sheath, as shown by
anatomical studies. Sciatic nerve divides into its two main branches generally
at lower thigh level, although this is very variable (0–13 cm from popliteal
crease).

97
Q

Parasacral block

A

Parasacral block (Mansour’s approach)
is a relatively easy block to
perform and has a high success rate.

unlikely to cause
hypotension.

98
Q

Parasacral block effect on BP

A

As sacral outflow is predominantly parasympathetic, sacral nerve
blockade causes parasympathetic blockade, hence is unlikely to cause
hypotension.

99
Q

Parasacral block & obturator

A

Obturator nerve can be reliably blocked either by a lumbar plexus
block or specific obturator block.
It is not reliably and consistently
blocked by either a fascia iliaca or sacral plexus block.

100
Q

(PCFN) vs parasacral tourniquet below knee

A

that posterior cutaneous femoral nerve (PCFN) block

provides better tolerance of a thigh tourniquet during below-knee surgery

101
Q

posterior cutaneous femoral nerve (PCFN)

supply

how can it be blocked

A

The PCFN has
no motor or articular supply.

It provides sensory innervations to the
lower buttock and posterior thigh and therefore is
important for prevention of thigh tourniquet pain,
in combination with
femoral nerve and LCN of thigh.

The PCFN may be blocked by
proximal approaches only (Mansour’s parasacral block, Labat’s gluteal,
Beck’s anterior approach).

However, a randomised study of proximal
and distal block has not revealed any statistical difference in thigh
tourniquet tolerance for below-knee surgery.

102
Q

Parasacral and what block for LL surgery

?femoral

A

Along with lumbar psoas compartment block (not femoral nerve

block) it may be used for unilateral lower-limb anaesthesia

103
Q

proximal sciatic nerve blockade approaches

A

Posterior transgluteal (Labat’s) approach:

Subgluteal approach (lateral):

Lithotomy subgluteal (Raj’s) approach

Infragluteal (Sukhani’s) approach:

Anterior (Beck’s) approach:

Subtrochanteric (Guardini’s) approach:

104
Q

Posterior transgluteal (Labat’s) approach:

A

Greater Troch (GT) and PSIS (line 1)
and another
between GT and sacral hiatus (line 2).

lateral decubitus

105
Q

Subgluteal approach (lateral):

A

lateral decubitus,

GT and the ischial tuberosity (IT)
midpoint

106
Q

Lithotomy subgluteal (Raj’s) approach

A

supine,

hip and the knee are flexed at 90

connecting GT and IT
midpoint

107
Q

Infragluteal (Sukhani’s) approach:

A

prone,

lateral border of the biceps femoris (BF) muscle is palpated

intersects the infragluteal crease is the point of

BF
twitches should not be accepted

108
Q

Anterior (Beck’s) approach:

A

ASIS and pubic tubercle

GT

109
Q

Subtrochanteric (Guardini’s) approach:

A

Subtrochanteric (Guardini’s) approach: with patient supine, GT is
palpated.

110
Q

Mansour’s
parasacra

adv disadv

A 
Mansour’s
parasacral
Simple landmarks
Easy to perform
High success rate

Lateral positioning needed

111
Q

Labat’s posterior

transgluteal

A

Labat’s posterior
transgluteal

Proximal approach

Lateral positioning needed
Difficult landmarks
Painful needle insertion
Ultrasound guidance difficult since nerve is deeper at
this level
112
Q

Subgluteal

A

Subgluteal

Sciatic nerve is not covered
by gluteus

Reliable landmarks even in
obese individuals
Ultrasound guidance easier
to do

Lateral positioning needed Anisotropy of sciatic
nerve

113
Q

Raj’s lithotomy

A

Raj’s lithotomy

Supine positioning
Reliable landmarks

Procedural difficulty (someone needs to hold the leg,
and limb moves with stimulation)
114
Q

Sukhani’s infragluteal

A

Sukhani’s
infragluteal

Simple landmarks

Prone positioning needed
Landmarks may be variable (only bony landmarks
are fixed)
Spares the posterior cutaneous femoral nerve

115
Q

Beck’s anterior

A

Beck’s anterior

Supine positioning
Resurgence with ultrasound
guidance approach

Deeper insertions, hence painful
Technically challenging

116
Q

Guardini’s

A

Guardini’s
subtrochanteric

Supine positioning

Not a favoured approach

117
Q

sciatic nerve is composed of two components

A

sciatic nerve is composed of two components,

the tibial and the
common peroneal.

The tibial nerve (TN)
is larger and lies medially,

while the
common peroneal nerve (CPN) is
smaller and lies laterally.

118
Q

What does TN supply

A 
The TN 
supplies 
gastronemius, 
soleus and 
plantaris in the leg; 
and
flexor hallucis longus 
and 
flexor digitorum longus 
in the foot through
medial and lateral plantar nerves.

Stimulation of TN causes plantar
flexion.

119
Q

CPN divides into superficial+Deep

Superficial

A

The CPN divides into a superficial and a deep branch.

The superficial peroneal nerve supplies
peroneus brevis and longus,
which evert the ankle.

120
Q

Deep PN

A

The deep peroneal nerve supplies

branches to muscles of the
anterior leg
(tibialis anterior, extensor digitorum longus, peroneus tertius, and extensor hallucis propius)

and extensors of ankle

(extensor hallucis longus and extensor digitorum longus).

This causes dorsiflexion upon
stimulation

121
Q

What suggests best chance of success with EMR on sciatic nerve block

A

inversion of the foot

122
Q

inversion of the foot & Sciatic N block

A

inversion of the foot is caused by tibialis anterior
(deep peroneal nerve)
and tibialis posterior (the TN).

Hence, such a response suggests a central needle-tip location and stimulation of both TN and CPN components.

This has been the reason suggested for a higher success
rate and a shorter onset time of anaesthesia with inversion EMR.

123
Q

Sciatic Nerve block most common approach

A

Popliteal

most superficially at this level (2–4 cm).

separates into its two components: medial tibial nerve (TN)
and l
ateral common peroneal nerve (CPN)

variably above the popliteal crease from 0 to 13 cm

multistimulation or ultrasound guidance techniques enhance success rates (sparing d/t uneven division)

124
Q

Two approaches to PNS-guided popliteal block are in vogue

Posterior

A

Posterior approach:
the patient is positioned prone;

a triangle is
drawn over the posterior aspect
of the knee where the

popliteal crease forms the base,
biceps femoris tendon the lateral border
and
semimembranosus tendon the medial border.

A perpendicular line (P)
is dropped from the apex to the popliteal crease bisecting it.

A point 7– 8 cm above the popliteal crease
on this perpendicular line is chosen,
and a 50-mm 22-G needle is inserted 1 cm lateral to this point.

In most people, the sciatic nerve has not divided at this point.

Inversion
EMR yields best results followed by plantar flexion, dorsiflexion and
eversion.

A volume of 25–40 mL of local anaesthetic may be used.
The same landmark technique may be performed with the patient in
lithotomy position.

125
Q

Lateral approach

PNS-guided popliteal block

A

Lateral approach:

the groove between biceps femoris
and vastus lateralis is palpated,

and a 100-mm needle is inserted perpendicularly
7–8 cm above the popliteal crease.

The needle is walked off the
femur at an angle of 30° dorsal
to stimulate the sciatic nerves.

Common peroneal nerve is commonly
stimulated here, and the drug is
injected subsequently.

126
Q

Ultrasound-guided popliteal block

1 probe

2 issue wiht sciatic
how improved

A

1
This uses a high-frequency array
(6–13 MHz), as sciatic nerves are
located superficially.

2
The sciatic nerve is anisotropic, hence the beam needs to be aligned
at 90° to obtain the best view.
This can be achieved by a cranial tilt of
the probe at the proximal thigh,
vertical positioning at mid-thigh and a
caudal tilt at the lower-thigh level.

127
Q

Ultrasound-guided popliteal block

3 how is it located

4 then what after location

5 how to deposit local

A

3
The probe is placed parallel to popliteal crease, and moved upward until the pulsatile popliteal artery is seen.

The sciatic nerve components can
be seen superficial and lateral to the artery at this
level.

4
They may be traced upwards, where they are seen joining to form a single sciatic nerve.
This is the best location for injection as well as
catheter placement.

5
At this point, local anaesthetic is deposited in a circumferential manner to enclose hyperechoic nerve all around (the doughnut sign).

128
Q

Cutaneous nerve supply ankles

A

Cutaneous nerve supply of the ankle is important; it is derived from
five nerves,

Landmark Nerve
Lateral malleolus Sural
Superficial peroneal
Medial malleolus Saphenous
Dorsum of foot Mostly superficial peroneal
Plantar surface of foot Medial and lateral plantar (branches of tibial)
Lateral margin of foot Sural
Medial margin of foot Saphenous
Web space between the first and second toes Deep peroneal
Fifth toe Superficial peroneal
Heel Posterior tibial

129
Q

Ankle block

which are superficial and deep

A

The ankle is innervated by five nerves:

three nerves are superficial
(superficial peroneal,
sural
and saphenous),

and

two are located deep
(deep peroneal and posterior tibial).

Remember: S is superficial

130
Q

Injection landmarks for ankle block

Deep
peroneal

A

Deep peroneal

Peripheral nervous system:
lateral to the tendon of the extensor hallucis longus
muscle (between extensor hallucis longus and extensor digitorum longus)

Ultrasound: nerve is immediately lateral to the dorsalis pedis artery

131
Q

Injection landmarks for ankle block

Posterior Tibial

A

Posterior tibial

Behind medial malleolus, deep to posterior tibial artery

132
Q

Injection landmarks for ankle block

Saphenous

A

Saphenous

Subcutaneously at medial malleolus near great saphenous vein

133
Q

Injection landmarks for ankle block

Sural

A

Sural

Subcutaneously in the groove between lateral malleolus and calcaneum (behind
short saphenous vein)

134
Q

Injection landmarks for ankle block

Superficial peroneal

A

Superficial peroneal

Subcutaneously between anterior tibial and lateral malleolus

135
Q

The duration of analgesia provided for foot surgerie

Subcut infiltration

ankle block

popliteal block

A

The duration of analgesia provided for foot surgeries is 6 hours by
subcutaneous infiltration, 11 hours by ankle block and 18 hours by
popliteal block.

136
Q

Mayo block

A

Mayo block is an alternative
to ankle block for bunion or hallux
surgery, as it anaesthetises the first metatarsal only.

137
Q

Adrenaline and ankle blokcs

A

Adrenaline should ideally be avoided in ankle blocks because of the
risk of vascular compromise.

EDRA (26 decks)

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