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fascia lata / fascia iliacus nerve block


  • the fascia lata or fascia iliaca block is a high volume local anaesthetic block of both the femoral nerve and the lateral cutaneous nerve of the thigh via injection of low concentration, LA into the compartment space below the fascia iliacus
  • it does not block the sciatic nerve and does not reliably block the obturator nerve
  • initially described by Dalens et al. on children
  • it is now mainly used in the ED for pain relief in patients with fracture neck of femur (#NOF)

compared with femoral nerve block

  • technically easier and safer than the traditional femoral nerve block
  • may not produce as dense a block as LA solution is lower concentration to allow the higher volume
    • thus the iliacus block is ideal for analgesia for #NOF in ED BUT it is NOT for surgical anesthesia
    • also it is less likely to block motor fibres
unlike the traditional femoral nerve block, high volume infiltration is CRITICAL to the success of the fascia iliacus block - volume of LA should be 30-50ml, hence lower concentrations are required to avoid toxicity


  • patient refusal
  • local inflammation or infection in the groin
  • groin masses distorting anatomy
  • PH femoral bypass graft
  • septic arthritis of hip joint


femoral nerve

  • largest branch of the lumbar plexus, originating from the posterior divisions of the anterior rami of the lumbar nerves 2, 3 and 4
  • enters the thigh behind the inguinal ligament, lying lateral to the femoral artery and on top of the iliacus muscle. It is separated from the artery by the fascia iliaca.
  • gives motor supply to the knee extensors (quadriceps femoris and sartorius muscles) and sensory supply to the anteromedial surface of the thigh and the medial aspect of the lower leg, ankle and foot via its terminal branch, the saphenous nerve.

lateral femoral cutaneous nerve of the thigh

  • arises from L2 and L3
  • emerges from the lateral border of the psoas major muscle and runs on the ventral surface of the iliacus muscle, heading towards the anterior superior iliac spine (ASIS).
  • it is covered on its course by the fascia iliaca.
  • passing behind the inguinal ligament close to its lateral insertion at the ASIS, it perforates the fascia iliaca
  • in the thigh it splits into its terminal cutaneous branches, which usually cross over the sartorius muscle and are covered by the fascia lata.
  • gives sensory supply to the lateral aspect of the thigh as far distal as the knee.

fascia iliaca

  • from the lower thoracic vertebrae to the anterior thigh
  • lines the posterior abdomen and pelvis, covering psoas major and iliacus muscle
  • forms the posterior wall of femoral sheath, containing the femoral vessels
  • above the inguinal ligament the femoral vessels lie superficial to the fascia iliaca while the femoral, obturator and LFCN are covered by it.
  • under the inguinal ligament:
    • medially, the fascia iliaca forms the posterior wall of the femoral sheath (lacuna vasorum), which contains the femoral artery and vein and the femoral branch of the genitofemoral nerve.
    • laterally:
      • it forms the roof of the lacuna musculorum, which contains the psoas major and iliacus muscles and the femoral nerve. T
      • the fascia iliaca separates the lacuna musculorum from the lacuna vasorum with fibres that link to the capsule of the hip joint, thereby forming a functional septum between the two lacunae.

fascia lata compartment

  • a potential space between the fascia lata and the deeper fascia iliacus
  • contains the LFCN, femoral branch of the genitofemoral nerve and the femoral vessels but NOT the femoral nerve

fascia iliaca compartment

  • a potential space under the fascia iliacus and above the anterior surface of iliacus and psoas major muscles which contains the femoral nerve and medially, the anterior and posterior branches of the obturator nerve but NOT the distal part of LFCN, nor the femoral vessels
  • craniomedially it is continuous with the space between quadratus lumborum mucle and its fascia
  • LA injected into this space will tend to travel cranially towards the lumbar plexus nerves and thus acting on all three nerves to varying degrees: lateral femoral cutaneous nerve, the femoral nerve and the obturator nerves.


  • anatomic landmark for injection:
    • 1cm below the inguinal ligt (line from ASIS to pubic tubercle) at the junction of the middle and lateral thirds of this line (ie. 1/3rd of the way from ASIS)
    • NB. this is lateral to the femoral nerve which is laterla to the femoral artery!
    • the femoral artery pulse should be palpable 1.5 to 2 cm medial to the intended injection point to ensure a safe distance from the femoral nerve to avoid femoral nerve impalement.
  • 1% lignocaine LA to skin at injection site
  • needle insertion technique if used without ultrasound guidance:
    • aim cranially at 60deg angle to skin using a blunt/short bevel needle such as a Tuohy needle.
    • advance the needle through two distinct “pops” as it perforates first the fascia lata, then the fascia iliaca (the latter of which gives a more subtle “pop”).
      • if you don't feel the 2 pops, re-try with needle more perpendicular to skin and more cranial
    • reduce the angle between needle and skin surface to about 30 degrees and advance the needle further 1-2 mm.
    • aspirate before injection and after every 5 ml injected to ensure you are not in a blood vessel
      • if blood is aspirated, withdraw needle, apply pressure for 2 minutes then re-try more laterally
    • start infiltrating with LA
    • if resistance to infiltration then withdraw 1mm or so as needle tip may be in the muscle
    • injection should not cause pain nor paraesthesia
      • stop injecting if severe pain
      • if mild burning sensation, slow infiltration rate
  • no pain relief within 30 minutes
    • consider injecting a further 20ml low concentration LA
  • use of ultrasound to aid identification of the fascial planes may lead to faster onset, denser nerve blockade and an increased rate of successful blocks.
    • the simplest way to find the correct fascial layer is to clearly identify the ilium (bone) on ultrasound. The muscle lying in contact with the bone and directly overlying it, is the iliacus muscle and so the fascial layer covering it is the iliacus fascia.1)

local anaesthetic agent

  • ropivacaine 0.75% (7.5mg/1mL Naropin) is the drug of choice for fascia iliacus blocks:
    • Dose: 1-3mg/kg (usual range of 75mg-300mg) 150mg is appropriate for many patients, max. 300mg
    • unless pt weighs less than 50kg, then max dose is calculated using 3mg/kg
    • most patients will receive 150mg (20mL) of 0.75% Ropivacaine, diluted with 10mL of 0.9% NaCl to 30mL total.
    • in greater doses, dilute to 40-50mL with 0.9% NaCl
fasciailiacusblock.txt · Last modified: 2013/08/01 06:22 by

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