Femoral Nerve Block

Other Names

• Femoral Nerve Injection
• Femoral Nerve Block

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Background

Key Points

• Needle: 22-25 gauge, 1.5-3.5 inch needle
• Transducer typically linear but depends on body habitus
• Use femoral triangle to orient to the anatomy

Anatomy of the Femoral Nerve

• Runs deep to Iliacus and superficial to Psoas muscles
• It is the most lateral component of the femoral triangle

Palpation Guidance vs Ultrasound Guidance

• It is strongly encouraged that this block be performed under ultrasound guidance
• General studies have shown that ultrasound improves speed and efficiency

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Indications

• Diagnostic Block
• Femoral Nerve Injury
• Therapeutic Block for certain fractures such as:
  • Hip Fracture
• Operative block for:
  • Total Hip Arthroplasty

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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

Illustration of short axis in plane approach with needle visualized

Ultrasound of short axis, in plane approach with labels

Short axis, in plane approach needle and probe position

Ultrasound of short axis, out of plane approach

Short axis, out of plane approach needle and probe position

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

• Best visualized in short axis using the high frequency linear transducer
• Femoral Nerve
  • Depth is less than 3 cm in a non-obese patient
  • Triangular hyperechoic region lateral to femoral artery, adjacent to iliacus
• Abnormal findings are uncommon

Technique: Short Axis, In Plane

• Patient Position
  • Supine, hip slightly flexed
• Transducer position
  • Short axis to femoral nerve
  • Orient lateral to femoral artery
• Needle Approach/ Orientation
  • Lateral to medial
  • In plane
• Target
  • Lateral aspect of the femoral nerve
• Pearls and Pitfalls
  • Orient to the femoral triangle to avoid injecting near/around the vessels
  • Scan cranial to caudle to identify largest diameter of nerve

Technique: Short Axis, Out of Plane

• Patient Position
  • Supine, hip slightly flexed
• Transducer position
  • Short axis to femoral nerve
• Needle Approach/ Orientation
  • Out of plane
  • Distal to proximal using step-down technique
• Target
  • Femoral nerve sheath
• Pearls and Pitfalls
  • Orient to the femoral triangle to avoid injecting near/around the vessels
  • Difficult to track needle tip increasing risk of intravascular/intraneural injection

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Aftercare

• Can augment with ice, NSAIDS
• Patients with femoral nerve block will temporarily be unable to walk following the block

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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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