Lateral cutaneous nerve of thigh


It is a branch of the lumbar plexus.  It is formed in the substance of psoas muscle from the dorsal divisions of second and third lumbar nerves.  It emerges from lateral end of the psoas muscle lying over the iliacus muscle under the cover of iliac fascia.  It runs obliquely across the iliac muscle towards the anterior superior iliac spine.  It passes  underneath the inguinal ligament and the pierces the lilac fascia to lie over the anterior surface of the Sartorius muscle.  It then lies between the Sartorius and tensor fascia lata muscle sandwitched between fascia iliaca and fascia lata. Nerve is seen to lie in a hammock formed by the iliac fascia as it passes over the Sartorius and tensor fascia lata  

How to locate the LFCN:

1.Incision on the lateral side of thigh: e.g. surgery for fracture neck of femur.
2.Skin graft from lateral side of thigh

Contraindications:  Absolute contraindications are patient refusal and infection at the site of block.


1.Ultrasound machine with high frequency linear probe
2.Stimuplex or equivalent 100 mm needle
3.Chlorhexidine 2%  for asepsis
4.Local anaesthetic:  5-10 ml of local anaesthetic (for analgesia 0.25% and anaesthesia 0.5%)


Patient lies supine.  Anaesthetist stands on the side of the patient the block is going to be done. The machine is positioned as shown in the picture so that everything is easily visible and accessible to the anaesthetist picture Ultrasound probe is placed below the inguinal crease and parallel to it so that a cross sectional view of a single femoral artery is obtained.  Femoral artery,nerve and iliac fascia are identified. Sartorius muscle is then identified.  The probe is then centered over the Sartorius muscle and turned in such a way that a good cross sectional view of the Sartorius muscle is obtained.  Probe is moved laterally so that the tensor fascia lata is visulaised .  Nerve will be then seen between as described before. Needle is introduced in-plane so that the entire needle is visualized. Local anaesthetic is then injected.