Sural Nerve Block - Technique, Indication, Contraindications, and Complications

Introduction

A localized anesthetic technique termed the sural nerve block is used in addition to general anesthesia during foot and ankle surgery. Sural peripheral nerve blocking is a relatively simple procedure since the sural nerve runs superficially above and near the ankle. Sural nerve blocks are routinely used in medical pain management and surgical treatments. In this method, the sural nerve, which is located in the calf of the leg, is specifically targeted for local anesthetic injection. The technique efficiently blocks nerve signals to temporarily relieve pain and suffering coming from the lateral side of the foot and ankle. Sural nerve blocks are frequently used by doctors for many purposes, including ankle surgery, managing chronic pain (pain lasting for a long time), and performing podiatric procedures. As a result of this minimally invasive process, patients are relieved from pain, which also enables medical personnel to carry out important treatments with more accuracy and patient comfort.

What Is a Sural Nerve?

The sural nerve is located in the rear of the lower leg (calf muscles), just below the skin's surface. It is a part of the peripheral nervous system, which makes it simpler for the brain and the rest of the body to communicate. It is a sensory nerve that helps in feeling touch, temperature, vibration, pain, and food position. Additionally, it can be used as donor tissue to identify and treat other nerve illnesses.

What Is a Sural Nerve Block?

For treatments affecting the foot and ankle, the sural nerve block is a regional anesthetic method that is frequently used as an addition to or an alternative to general anesthesia. The sural nerve, which passes superficially above and around the ankle, is numbed with this technique. Although a more modern technique is ultrasound-guided sural nerve blockage, the nerve's tiny size frequently makes visualization difficult. Perivascular techniques have shown improved block success rates in this situation. Peripheral nerve blocking of the sural nerve is a feasible alternative for foot and ankle surgery because it is simple.

A classic ankle block involves a combination of peripheral nerve blocks targeting four major nerves around the ankle: the superficial peroneal, deep peroneal, saphenous, and tibial nerves. Depending on the specific surgical approach, the inclusion of a sural nerve block might vary. However, it is advisable for the doctor to incorporate the sural nerve block regardless of the surgical site within the foot. This is because it is commonly desired to achieve a thorough sensory nerve block in the lateral foot and ankle, including deep sensations like vibration perception, to improve patient comfort.

How Is a Sural Nerve Block Administered?

• Equipment Required:

  1. Povidone iodine or Chlorhexidine gluconate.

  2. Ultrasound probe with a high frequency, sterile probe cover, and gel.

  3. Local anesthetic for superficial numbing, generally 1 percent Lidocaine.

  4. A syringe with an extension tube, 10 to 20 milliliter (ml).

  5. The 22-gauge short bevel block needle.

• Procedure:

  1. Conventional Approach - In the conventional method, the lateral malleolus (the noticeable bone at the end of the fibula on the outside of the ankle) and the Achilles tendon (the tendon that connects the heel to the calf muscles) are palpated in order to visually identify them. The needle is inserted with a trajectory targeted towards the lateral malleolus at the level of the superior malleolar border and laterally to the Achilles tendon. If paresthesia develops, the needle is stopped moving forward, and after a successful aspiration, a small amount of local anesthetic (approximately 0.1 fluid ounce) is administered. If there is not any paresthesia felt, the needle is moved forward until it touches the lateral malleolus bone, at which point a local anesthetic is given, and the needle is removed. In addition to anesthesia in the posterolateral calf and dorsolateral fifth digit, a good block may also be indicated by loss of sympathetic tone with color and rubor (color changes to red) of the foot.

• Ultrasound-Guided Approach -

  1. An ultrasound-guided sural nerve block is frequently carried out at the ankle level.

  2. The Achilles tendon and the posterior border of the lateral malleolus are important anatomical markers that must be recognized during the process.

  3. The Achilles tendon and the lateral malleolus are chosen as the designated locations. In the designated location, a high-frequency (10 to 18 megahertz) ultrasonic probe is positioned transversely.

  4. Ultrasonography is used to identify the saphenous vein. Around the lesser saphenous vein (the vein that runs through the leg), 0.1 fluid ounce of local anesthetic are injected for the block.

  5. Alternatively, an in-plane technique may be used, with the block needle moving towards the sural nerve from posterior to anterior. In order to identify the sural nerve, a calf tourniquet or a dependent posture of the leg may enhance vein size.

  6. It is advised to use an in-plane block to provide improved needle visibility.

  7. Since the sural nerve can be directly seen through ultrasound, less local anesthetic is needed for an effective nerve block, and the risk of a neural or vascular injection is also reduced.

What Are the Indications and Contraindications of a Sural Nerve Block?

• Indications:

  1. Wound investigation or repair for the dorsolateral (back or upper part and the sides both are involved) fifth digit or lateral posterior (back and side) calf muscles.

  2. For ankle block procedure which is necessary for the manipulation of a fractured or dislocated ankle.

  3. Foreign substance removal from the dorsolateral fifth digit or lateral posterior calf.

  4. Abscess removal and drainage in the laterodorsal fifth digit or lateral posterior calf muscles.

• Contraindications:

  1. Allergy to anesthetics or their additives (such as ester or amide).

  2. Administering an injection through tissue that is already infected.

  3. A severe bleeding problem.

  4. Noncompliance on the part of the patient, which may need anesthesia, especially in children or the elderly.

  5. Previous neurological injury or damage.

What Are the Complications of Sural Nerve Block?

• Pain on Injection - When receiving an injection, some people may feel pain or discomfort because the needle has punctured the skin and underlying tissues.

• Bleeding - Due to the penetration of blood vessels during the injection procedure, there could accidentally be a little bleeding at the injection site.

• Infection - If suitable sterile procedures are not used during the injection execution, there is a danger of infection, which might result in irritation and other consequences.

• Allergic Response - In certain instances, people may be allergic to the injection's ingredients, such as the drug or the preservatives, which might cause an allergic response.

• Nerve Damage - Nerve damage brought on by improper needle insertion can produce symptoms including tingling, numbness, or even loss of motor function.

• Pain - It can result in severe pain and possible nerve damage if the needle point is positioned under the fascia (a fine connective tissue sheath that envelops and stabilizes every organ, blood artery, bone, nerve fiber, and muscle), perineural (around a nerve), or intraneural (inside a nerve).

Conclusion

In the context of medical treatments and pain management, the sural nerve block is a useful technique. Its importance stems from its capacity to deliver localized relief, improve patient comfort, and facilitate successful surgical or therapeutic operations affecting the foot and ankle. The sural nerve block has been shown to be effective in reducing pain, and it is often used in various medical settings, strengthening its position as a critical strategy for healthcare practitioners. This approach is an example of medical development targeted at improving both therapeutic efficacy and patient pleasure since it strikes a balance between accuracy and patient well-being.