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Saphenous Nerve Injection

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Other Names

  • Saphenous Nerve Injection
  • Saphenous Nerve Block
  • Adductor Canal Block

Background

Saphenous nerve in the distal third of the thigh[1]
Reverse Ultrasound Anatomy for an adductor canal block with needle insertion in-plane and local anesthetic spread (blue). FA, femoral artery; FV, femoral vein; AMM, adductor magnus muscle; ALM, adductor longus muscle; VMM, vastus medialis muscle; SaM, sartorius muscle; SaN, saphenous nerve.[2]

Key Points

  • Needle: 2-3 inches, 22-25 gauge
  • Transducer: high frequency linear

Anatomy of the Saphenous Nerve

  • Distal cutaneous branch of the femoral nerve
  • Supplies innervation to the medial knee, leg and foot
  • Arises from the posterior division of the femoral nerve at the mid thigh
  • Accompanies the femoral artery within the adductor canal
  • The saphenous nerve exits the canal via the adductor hiatus
  • Here, it pierces the fascia between sartorius and gracilis
  • It then travels superficially along the medial side of the leg
  • Accompanying the saphenous vein

Palpation Guidance vs Ultrasound Guidance

  • This procedure can not be safely or reliably performed by landmark guidance
  • There are no papers comparing landmark to ultrasound guidance

Indications

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

Procedure

(A) Needle and probe position and (B) View of short axis in plane approach[3]

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

  • Common ultrasound findings include:
    • Patients may report pain on sonopalpation
    • Occasionally, a neuroma can be seen

Technique: Short Axis, In Plane

  • Patient Position
    • Supine
    • Leg is externally rotated and knee slightly flexed
  • Transducer Position
    • Short axis to saphenous nerve
  • Needle Approach/ Orientation
    • In plane
    • Anterior to posterior/ posterior to anterior
  • Target
    • Directly adjacent to the saphenous nerve
  • Pearls and Pitfalls
    • Nerve is sometimes difficult to visualize
    • Can inject into the fascial plane adjacent to the nerve
    • Femoral vessels can serve as a landmark

Aftercare

  • Motor exam should be intact
  • No major restrictions in most cases
  • Can augment with ice, NSAIDS
  • Consider Knee Compression Sleeve

Complications

  • Infection
  • Damage to surrounding tissue

See Also

References

  1. ↑ Malanga, Gerard A., and Kenneth R. Mautner. "Atlas of ultrasound-guided musculoskeletal injections." (No Title) (2014).
  2. ↑ Image courtesy of nysora.com
  3. ↑ Image courtesy of aneskey.com
Created by:
John Kiel on 17 April 2025 14:03:35
Authors:
Last edited:
17 April 2025 15:08:31
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