Lateral Femoral Cutaneous Nerve Injection

Other Names

Drawing of the course of the lateral femoral cutaneous nerve (LFCN) and its relation to muscles, fascias and the inguinal ligament

• Lateral Femoral Cutaneous Nerve Injection
• LFCN Injection
• Meralgia Paresthetica Injection
• Lateral Femoral Cutaneous Nerve Hydrodissection
• Lateral Femoral Cutaneous Nerve Block

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Background

Key Points

• Needle: 1.5 - 2 inches, 25 gauge
• Transducer: linear, high frequency
• LFCN is best found just distal to ASIS

Anatomy of the Lateral Femoral Cutaneous Nerve

• Sensory only nerve derived from the lumbar plexus, typically L1 to L3
• Tracks along the psoas major, iliacus and anterior superior iliac spine
• Then emerges under the inguinal ligament
• Provides sensory distribution to the anterolateral thigh
• Significant anatomic variance in approximately 25% of patients

Palpation Guidance vs Ultrasound Guidance

• We strongly recommend you use ultrasound guidance to perform this procedure
• Ng et al compared ultrasound vs landmark based approach on cadavers
  • They found 16/19 needles inserted under ultrasound guidance were in contact with the nerve while only 1 of 19 needles using anatomical landmarks was in contact with the nerve
• Another study found the landmark based technique was not effective

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Indications

• Meralgia Paresthetica

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Contraindications

• Absolute
  • Anaphylaxis to injectates
  • Overlying cellulitis, skin lesion or systemic infection
• Relative
  • Can be treated with less invasive means
  • Hyperglycemia or poorly controlled diabetes
  • Lack of symptom improvement with previous injection

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Procedure

Needle and probe position for short axis, out of plane approach

Sonogram of lateral femoral cutaneous nerve (arrowhead) 3 finger breadths caudal to the ASIS

Reverse Ultrasound Anatomy and sonoanatomy of the lateral femoral cutaneous nerve (A) before and (B) after injection. ASIS, anterior superior iliac spine; LFCN, lateral femoral cutaneous nerve; FL, fascia lata; FI, fascia iliaca; SAR, sartorius muscle. The solid arrow heads indicate the needle path.

Equipment

• Sterile prep (i.e. chloraprep, chlorhexidine, iodine, etc)
• Gloves
• Needle: typically 21-25 gauge, 1.5 inch
• Syringe: 5-10 mL
• Gauze
• Ethyl Chloride
• Bandage
• Injectate
  • Local anesthetic
  • Corticosteroid
• Sterile probe cover

Ultrasound Findings

• Finding the LFCN
  • Most asily located by placing the transducer in short axis just distal to ASIS
  • Identify sartorious (medial) and tensor fascia lata
  • The nerve can be identified in a small superficial triangular lacuna
• It can be traced proximally to the inguinal ligament
  • Alternative approach
  • Place the transducer on the long axis of the inguinal ligament
  • LCFN typically passes under the ligament about 1 cm medial to ASIS
  • Due to variability, can be as far as 4 cm medial

Technique: Short axis, In plane

• Patient Position
  • Supine
• Transducer position
  • Short axis to the nerve
  • Can turn long axis if performing hydrodissection
• Needle Approach/ Orientation
  • In plane
  • Lateral to medial
• Target
  • Lateral femoral cutaneous nerve
• Pearls and Pitfalls
  • Can perform hydrodissection in an in/out of plane technique
  • Remember the nerve is very superficial

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Aftercare

• Can augment with ice, NSAIDS

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Complications

• Skin: Subcutaneous fat atrophy, skin atrophy, skin depigmentation
• Painful local reaction
• Infection
• Hyperglycemia
• Tendon, nerve or blood vessel injury

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See Also

• Procedures Main
• Ultrasound Main
• Back Pain Main
• Hip Pain Main

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