Chapter 143. Lateral Femoral Cutaneous Nerve Block

Anatomy:

The lateral femoral cutaneous nerve (LFCN) arises from L2–3. After emerging from the lateral border of the psoas major muscle, it courses inferiorly and laterally toward the anterior superior iliac spine (ASIS). It then passes under the inguinal ligament and over the sartorius muscle into the thigh, where it divides into two branches (anterior and posterior). The LFCN, a small subcutaneous nerve located between the fascia lata and iliaca, provides sensory innervation to the lateral thigh. On occasion, its area of coverage can include the anterior thigh, normally covered by the femoral nerve.

Indications:

• Rare, as the LFCN is usually blocked when performing a femoral nerve block or a psoas compartment block. Rescue block in case of failure of the LFCN to be blocked
• Skin graft harvesting on the lateral aspect of the thigh

Contraindications:

None specific.

Technique using landmarks:

• Patient supine, palpate the ASIS
• Mark a point 1 cm medial and caudal to the ASIS
• After local anesthesia and prepping, insert a short-bevel 50 mm needle until a pop is felt, marking the passage through the fascia lata. The needle is moved fanwise laterally and medially, and 10–15 mL of solution is injected above and below the fascia

Technique using US:

• Small nerve, difficult to visualize
• Place high-frequency probe medial and inferior to the ASIS, parallel to the inguinal ligament
• In that area, the nerve should be between fascia lata and fascia iliaca. On occasion, it can lie deep to the fascia iliaca

Testing:

• Pinch/pinprick of skin of lateral aspect of thigh
• No motor block

Complications/side effects:

None specific.