The curriculum asks for knowledge on 'the principles of performing the following regional... procedures: lower limb blocks [femoral, sciatic and ankle]'.
The topic formed part of a CRQ in September 2024, with marks lost on 'benefits of peripheral nerve block, advantages of US v landmark technique'.
First described in 1989, the fascia iliaca compartment block is a fascial plane block technique, which aims to block:
The femoral nerve
The obturator nerve
The lateral cutaneous nerve of the thigh
It is essentially an anterior approach lumbar plexus block
Original landmark techniques had low success rates for anaesthetising all three nerves (38%)
Ultrasound-guided approaches improved block rates, be it via infrainguinal (67%) or suprainguinal (86%) approaches
Lumbar plexus
The lower roots of the lumbar plexus forms nerves which can be grouped into anterior (ventral) and posterior (dorsal) divisions:
Anterior divisions
Obturator nerve (L2-4)
Accessory obturator nerve (L3 & L4)
Posterior divisions
Lateral cutaneous nerve of the thigh (L2 & L3)
Femoral nerve (L2-4)
The femoral nerve runs deep to the fascia iliaca as it passes beneath the inguinal ligament, to lie lateral to the femoral vasculature
The lateral cutaneous nerve of the thigh also lies under the fascia iliaca
It passes obliquely over the iliacus muscle towards the ASIS
As it passes under the inguinal ligament it becomes superficial, dividing into anterior and posterior branches
These supply the lateral aspect of the thigh and inferolateral quadrant of the buttock respectively
Hip surgery - relevant innervation
The sensory supply to the hip demonstrates significant inter-individual variability
Nociceptors are concentrated in the superior aspect of the capsule, while mechanoreceptors are concentrated anteriorly
Articular branches of the femoral nerve and obturator nerve consistently provide anterior joint capsule innervation; the accessory obturator nerve less consistently so
The articular branches provide superomedial (femoral), lateral (femoral) and inferomedial (obturator) joint capsule innervation
The femoral articular branches arise above the inguinal ligament in 92% of cases; the obturator nerve-derived articular branches in 62%
Distribution
Femoral nerve
Dermatomes: antero-medial thigh down to and including the knee, with variable distal medial anaesthesia in the saphenous nerve distribution
Osteotomes: anterior hip joint, femur down to knee, patella
Lateral cutaneous nerve of the thigh
Dermatomes: anterolateral thigh
Obturator nerve
Dermatomes: medial, distal thigh
Osteotomes: anterior hip joint, medial aspect of femoral shaft
Indications
Hip fracture; for pre-, peri- or post-operative analgesia
Femoral shaft fractures
Anterior thigh surgery
Knee surgery including above-knee amputation
Contraindications
Previous femoral bypass surgery
Infection at intended block site
Local anaesthetic allergy
Patient refusal
Lack of appropriate resources
Standard regional anaesthetic set-up
Patient consent obtained
Ensure appropriate equipment available
Ensure adequate staffing i.e. trained assistant
Access to resuscitation equipment including intralipid
Patient awake or asleep, supine ± retraction of abdominal apron by assistant
Ultrasound machine on contralateral side with ergonomic set-up at anaesthetists discretion
50mm or 80mm echogenic short-bevel needle
Full aseptic precautions
Local anaesthetic
As a plane block, larger volumes of local anaesthetic are required
Typically this takes the form of 30-40ml 0.25% (levo)bupivacaine
Studies suggest 40ml local anaesthetic is required for successful supra-inguinal block
Infra-inguinal approach
Although a landmark technique is described, ultrasound is associated with:
Better sensory anaesthesia across all three nerves' distributions
Greater chance of achieving femoral nerve and obturator nerve block
Identify location of femoral vasculature at the inguinal ligament
Scan laterally to identify the iliacus muscle, lying lateral to the femoral vasculature but medial to the ASIS
Adjust transducer anisotropy as necessary to optimise fascia iliaca appearance
Either in-plane or out-of-plane approach
Once needle tip is correctly sited under the fascial iliaca, injection of local anaesthetic should cause separation of the iliacus muscle from the fascia
Local anaesthetic should spread medially and laterally
Supra-inguinal approach
Causes spread of local anaesthetic more proximally, improving anaesthesia of the femoral and lateral cutaneous nerves within the iliac fossa
Technique
Place transducer in para-sagittal place over ASIS, i.e. on a line connecting ASIS and umbilicus
Identigy the ASIS, and the iliacus muscle by sliding the probe infero-medially along the inguinal ligament
One should be able to identify the ASIS, iliacus, deep circumflex iliac artery, layers of the abdominal wall and potentially peritoneum
An in-plane approach is used, with the needle tip again positioned under the fascia iliaca and injection of local anaesthetic in this plane
Overall low rate of adverse effects and events
Lower risk of neurapraxia than femoral nerve block as needle not placed adjacent to the femoral nerve
Injection-site haematoma is the most frequently reported complication (1.7%)
Other complications are rare e.g. bladder injury
Theoretical risk of peritoneal cavity breach and viscal injury with suprainguinal approach
May be appropriate in certain patient groups e.g.: