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Posterior Ankle Nerve Block

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Posterior Ankle Nerve Block, Regional Anesthesia of the Posterior Ankle, Posterior Tibial Nerve Block, Sural Nerve Block

  • Indications
  1. Anesthesia of the heel and sole of the foot
  • Precautions
  1. Avoid injecting directly into nerves
  2. Avoid injection into posterior tibial artery
  • Complications
  1. Permanent Neuropathy due to posterior tibial nerve injection (do not inject nerve)
  • Preparation
  1. Needle: 27 gauge 1.5 inch
  2. Anesthetic: Lidocaine 1%: two 10 ml syringes
    1. Consider Bupivicaine when longer duration is needed
  3. Bedside Ultrasound (high frequency linear probe) guidance is recommended
  • Technique
  1. Patient position
    1. Prone position
    2. Ankle slightly dorsiflexed
    3. Prepare the skin with betadine or hibiclens
  2. Ultrasound
    1. See Ankle Ultrasound
    2. Place probe in sterile sheath in short axis, proximal to medial malleolus by 1-3 cm
    3. Identify posterior tibial artery (initial easiest landmark) the vein
    4. Posterior tibial nerve (starry night appearance) lies posterior to artery (towards achilles tendon)
    5. Out-of-plane approach may be needed due to narrow space
  3. Injection site 1: Posterior tibial nerve (majority of heel and sole of foot)
    1. Anteror and medial to achilles tendon border
    2. Proximal to medial malleolus tip by 1-2 cm
    3. Anesthetize the skin first
    4. Insert needle toward tibial artery
      1. Attempt aspiration confirming not in tibial artery
      2. Inject 1-3 cc near and deep to tibial nerve
      3. May inject additional 3-5 cc superficial to nerve while withdrawing needle
  4. Injection site 2: Sural nerve (medial arch only)
    1. Lateral border of achilles tendon and
    2. Proximal to lateral malleolus tip by 1-2 cm
    3. Distribute anesthetic
      1. Redirect needle several times
  5. Warning: Distal Paresthesias with needle with injection
    1. Indicates needle is in nerve
    2. Do not inject here!
    3. Remove needle and reposition
  6. Assess degree of anesthesia
    1. Wait 10 minutes to assess anesthetic effect
    2. If inadequate effect after 10 minutes, may make a second block attempt, or choose alternative anesthesia
  • References
  1. Eicken and Rempell (2016) Crit Dec Emerg Med 30(4):3-11
  2. Pfenninger (1994) Procedures, Mosby, p. 1036-54
  3. Warrington (2016) Crit Dec Emerg Med 30(7): 12-13
  4. Salam (2004) Am Fam Physician 69(4):896 [PubMed]