Sciatic Nerve block / Fascia Iliaca

Question 1

Key Points

Answer 1

1. A sciatic nerve block can provide analgesia or anaesthesia for a wide range of lower-limb procedures.
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2. Ultrasound guidance allows visualisation of the sciatic nerve and surrounding anatomical structures.
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3. Understanding the relevant anatomy of the sciatic nerve is vital when considering the level at which to perform the block.
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4. An additional block of the lumbar plexus or its branches is required to provide complete anaesthesia for lower-limb surgery.
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5. Motor-sparing ultrasound-guided local anaesthetic injection techniques for the posterior knee are gaining popularity for total knee arthroplasty.

Question 2

Anatomy

Answer 2

The sacral plexus is derived from the
lumbosacral trunk (L4–L5) and
the first to fourth sacral anterior rami

emerges within the pelvis,
lying anterior to the piriformis muscle and posterior to the presacral fascia

sacral plexus is the sciatic nerve (SN),

although other clinically relevant branches

include the posterior
femoral cutaneous nerve (PFCN),
the superior gluteal nerve,
and the nerve to quadratus femoris

Question 3

Labat (1923)

Answer 3

Lateral decubitus position

Operative side up, knee flexed

A line is drawn between the GT and PSIS.

At the midpoint of this line,

a second perpendicular line is drawn
caudad for 3 cm marking the point of needle insertion.

Question 4

Mansour

Answer 4

Mansour (1993) (sacral plexus block) Lateral decubitus position

Operative side up
A line is drawn between the midpoints of the PSIS and IT.

The point of needle insertion is 6 cm along this line from the PSIS. The needle is slowly advanced in a sagittal plane using nerve stimulation.

Question 5

Subgluteal approach

Answer 5

Subgluteal approach

Anatomy

This approach targets the SN as it traverses the subgluteal space,

between the IT and the GT.

The subgluteal space is a well-defined anatomical space

between the anterior surface of gluteus maximus and the

posterior surface of quadratus femoris.

The quadratus femoris muscle attaches to the posterior surface of the GT and IT, and runs deep to the subgluteal space.

Advantages
Reliable bony landmarks aid the identification of the SN at this location. However, injection of LA into the subgluteal space will provide an adequate block even if visualisation of the nerve is difficult

Question 6

Motor-sparing ultrasound-guided local anaesthetic infiltration techniques

Answer 6

iPACK

It targets the genicular nerves innervating the posterior knee joint capsule, which are supplied by articular branches of the sciatic and posterior obturator nerves

Postoperative analgesia is therefore provided to the posterior knee, with motor sparing of the TN and CPN

Question 6

Motor-sparing ultrasound-guided local anaesthetic infiltration techniques

Answer 6

iPACK

It targets the genicular nerves innervating the posterior knee joint capsule, which are supplied by articular branches of the sciatic and posterior obturator nerves

Postoperative analgesia is therefore provided to the posterior knee, with motor sparing of the TN and CPN

The patient is positioned in the supine position with the knee flexed and hip abducted. A curvilinear transducer (2–5 MHz) is placed on the medial aspect of the thigh just proximal to the popliteal crease, and the probe is then slid towards the posterior aspect of the popliteal fossa aiming to visualise the femoral condyles and popliteal artery. Injection of LA targets the interspace between these structures where the genicular branches lie.

Question 7

Clinical application

Answer 7

For surgery below the knee,

a popliteal approach provides adequate analgesia or anaesthesia

in combination with a saphenous nerve block if required.

However, this will not provide coverage for a thigh tourniquet.

For surgery above the knee, consideration should be given to the PFCN.

A proximal parasacral approach is required to reliably block both the
SN and PFCN, which is vital for awake surgery where total anaesthesia of the surgical site is required.

Regional anaesthesia for total knee arthroplasty has evolved in favour of motor-sparing techniques, such as US-guided infiltration of the posterior capsule (iPACK) in combination with an adductor canal block to facilitate earlier postoperative mobilisation.

However, an SNB remains a useful technique for patients at high risk of significant acute pain or postoperative opioid requirements.

Placement of a perineural catheter may be considered for certain lower-limb surgical procedures associated with significant postoperative pain, such as hind-foot surgery, ankle fusion, and ankle replacement.

Question 8

Conclusions

Answer 8

Sciatic nerve blocks can be used to provide anaesthesia or postoperative analgesia for a wide range of lower-limb procedures.

When considering which SN approach to use,

it is vital to understand the anatomy of the SN itself,

and the cutaneous, osseous, and muscular innervation provided by the nerve.

Ultrasound guidance allows visualisation of typical sonographic landmarks relevant to the safe performance of each approach.

Question 9

Fascia Iliaca

Answer 9

1 The hip is supplied by nerves arising from both lumbar and sacral plexuses.

2 Fascia iliaca compartment block (FICB) may be performed using a landmark or ultrasound-guided approach.

3 FICB is recommended for preoperative analgesia in patients with hip fracture.

4 FICB is opioid-sparing but does not provide complete analgesia for hip surgery.

5 As with any regional anaesthetic block, appropriate monitoring is needed to ensure safety

Question 10

Intro

Aim to block

Answer 10

anterior approach to the lumbar plexus where local anaesthetic (LA)

is injected proximally beneath the fascia iliaca,

with the aim of blocking the

1. femoral nerve (FN),
2. obturator nerve (ON),
3. and lateral cutaneous nerve of thigh (LCNT) simultaneously.

the needle is not directed to lie adjacent to the FN,
thus reducing the risk of neuropraxia.

In clinical practice, the FICB provides a safe and relatively simple alternative to femoral and lumbar plexus blocks.

Question 11

Anatomy

Answer 11

Innervation of the hip joint
The sensory nerve supply to the hip joint includes the

1 FN,

2 ON,

articular branches of the sciatic nerve, nerves supplying quadratis femoris, and superior gluteal nerve

Question 12

Fascia Iliaca

Answer 12

Fascia iliaca,
and its relationship to femoral,
lateral cutaneous,
and obturator nerves

The fascia iliaca compartment is a potential space lying between the

fascia ilaca anteriorly

and the iliacus and psoas muscles (iliopsoas) posteriorly

The fascia iliaca attaches to the iliac crest laterally and to the fascia overlying the psoas muscle medially

Question 13

Indications

Answer 13

Indications for FICB include
pre-, peri- and postoperative analgesia after fractured neck of femur (NOF)

hip and knee surgery, above knee amputation,

Question 14

, contraindications, and

Answer 14

. Contraindications include previous
femoral bypass surgery,
patient refusal,
allergy to LA, and infection at the block site.

oagulopathy, peripheral neuropathy, or neurological conditions

Question 15

complications

Answer 15

block failure,
haematoma,
neuropraxia,
local anaesthetic systemic toxicity (LAST),
quadriceps weakness,
perforation of peritoneal cavity contents and bladder puncture.

Question 16

Block technique

Answer 16

landmark-guided approach. Ultrasound guidance is now commonplace, however. Ultrasound has also facilitated the development of more proximal, suprainguinal approaches to the FICB. This is because successful blockade of LCNT and ON relies on proximal spread of LA as both of these nerves generally lie superior to the fascia iliaca distal to the inguinal ligament

Question 17

Landmark technique

Answer 17

Anatomical landmarks are the

inguinal ligament,

anterior superior iliac spine (ASIS),

and pubic tubercle.

Line connecting the ASIS
and the pubic tubercle is divided into thirds

The injection is performed at a point
1 cm caudad to the junction of the lateral
third and medial two thirds

A blunt, short-bevel needle is inserted perpendicular to the skin and the needle angle adjusted to approximately 60° and directed cranially. A ‘give’ or ‘pop’ may be felt as the needle passes through fascia lata, and a second ‘give’ as it passes through the fascia iliaca

The needle angle is adjusted to approximately 30° and advanced a further 1–2 mm. LA should be injected without experiencing resistance. If resistance occurs, the needle should be withdrawn slightly and injection reattempted after further aspiration.

Question 18

Ultrasound guided infrainguinal approach

Answer 18

Ultrasound guided infrainguinal approach
In the supine position as before,
a high frequency (6–14 MHz) linear

Probe is placed transversely to identify the
femoral artery at the inguinal crease

Iliopsoas muscle with the overlying
fascia iliaca is identified and the hyperechoic FN
is typically seen lying between the iliopsoas
and fascia iliaca at a depth of 2–4 cm

The probe may be tilted cranially and caudally
until optimal images of the FN and fascia iliaca are obtained

e triangular shaped sartorius muscle and the ASIS are identified on moving the probe laterally. After skin disinfection and LA infiltration, a 50–100 mm blunt ended needle is inserted using an in-plane technique with the aim of placing the needle tip beneath the fascia iliaca around the lateral third of a line between the ASIS and pubic tubercle

Correct needle placement is confirmed by separation of the fascia iliaca from the iliopsoas muscle with LA spreading towards the FN medially and the iliac crest laterally

Volumes of 30–40 ml, ensuring compliance with safe dose limits for the LA, are routinely used to ensure optimal spread.

Question 19

Suprainguinal

Answer 19

The probe is then moved laterally and superiorly along the inguinal ligament towards the ASIS to lie laterally to the FN

The deep circumflex artery is identified superficial to the fascia iliaca and 1–2 cm cephalad to the inguinal ligament, and this provides a further landmark for needle placement.

The needle is inserted 2–4 cm caudad to the inguinal ligament aiming ultimately to be beneath the fascia iliaca cephalad to the inguinal ligament.

The suprainguinal approach to the FICB has also been described using a more proximal needle insertion point.8

With the patient supine, a linear high frequency probe (6–14 MHz)
is placed in the sagittal plane to obtain an image of the ASIS

probe is moved medially and the fascia iliaca and sartorius, iliopsoas, and internal oblique muscles are identified

a 100 mm needle is introduced 1 cm cephalad to the inguinal ligament. Using an in-plane approach, the needle tip is positioned beneath the fascia iliaca, and hydro-dissection is used to separate the fascia iliaca from the iliacus muscle.

The deep circumflex artery lies superficial to the fascia iliaca and upward movement of this artery upon injection can be used as a marker of fascia iliaca penetratio

This is because successful blockade of LCNT and ON relies on proximal spread of LA as both of these nerves generally lie superior to the fascia iliaca distal to the inguinal ligament

Question 20

Use

Answer 20

Fractured NOF
se of FICB can provide effective pain relief whilst minimising systemic adverse effects

be superior to opioids for: pain control on movement, preoperative analgesic consumption, time to first analgesic request, and time to perform spinal

Total hip arthroplasty

Question 21

Training requirements for performance of FICB. FICB, fascia iliaca compartment block; LA, local anaesthetics; LAST, local anaesthetic systemic toxicity; USG, ultrasound guided.

Answer 21

Knowledge of relevant anatomy, landmarks, and sonoanatomy
Knowledge of ultrasound physics, ‘knobology’ for USG technique
Knowledge of indications and contraindications for FICB
Knowledge of LA pharmacology
Knowledge of signs and symptoms of LAST
Knowledge of treatment of LAST
Development of technical skills for both USG and landmark techniques

Question 22

Conclusion

Answer 22

FICB is a safe and simple means of providing analgesia for procedures involving the hip joint and femur. The USG suprainguinal approach appears to be most effective at achieving successful block of all three nerves, although technically it may be more challenging to perform. FICB is particularly valuable in patients admitted with hip fracture resulting in opioid sparing and improved dynamic analgesia. The role of FICB in elective hip surgery requires further clarification.