Peripheral nerve blocks are highly effective anaesthesia and analgesia technique with low technical risk for ankle and foot surgery, They are appropriate and convenient technique for Ankle and foot Ambulatory surgery.

Depending of the tourniquet positioning the anaesthesia of the Ankle and foot can be organized using proximal or distal block. Proximal blocks are necessary when using a thigh tourniquet and distal blocks are efficient when using an ankle tourniquet.

1. Thigh tourniquet with proximal blocks for ankle and foot surgery.

Using a thigh tourniquet, a sciatic and femoral nerve blocks should be performed.²

1–1 Femoral nerve block:

When using an in plane technique, the puncture site is located at the outer lateral end of the probe. Advance the needle parallel to the long axis of the probe in the same plane as the ultrasound beam in the direction of the femoral nerve, lateral to the femoral artery. When the tip of the needle crosses both fascia lata and iliaca, a typical click can be perceived and confirmed on the screen. Once the needle is adjacent to the nerve, inject 15–20 ml of local anaesthetic. At this level, before separating, the saphenous nerve, its terminal branch, is usually situated on the anterior and medial surface of the femoral nerve. The femoral nerve block allowing to anesthetize the saphenous nerve also gives an anaesthesia at the medial part of ankle and foot. The saphenous nerve is also an important contributor to postoperative pain after major ankle surgery.³

1–2 Sciatic nerve block:

Because of its widespread use for ankle and foot surgery and its excellent visualization, the sciatic nerve block is one of the most commonly lower limb nerve block performed under US guidance. The lateral approach allows an optimal visualization of the needle during its entire travel to the nerve.

When using an in plane approach, the puncture site is located at the outer lateral end of the probe. Insert the needle then advance towards the sciatic nerve performing a Subgluteal or

a Popliteal nerve block.

When performing a popliteal nerve block using an in plane technique (supine), identify the needle tip and direct the needle medially between biceps femoris and vastus lateralis muscles and then through the biceps femoris towards the sciatic nerve.

Position the needle either deep or superficial, close to the nerve; avoid direct contact with the nerve. Inject local anaesthetic and observe spread.

When 15–20 mL is injected, a circumferential or extensive, close to the nerve, proximal spread of the local anaesthetic solution is noted in most patients, resulting in a subparaneural injection allowing in a rapid and complete anaesthesia of the foot.

There appears to be a distinct fascial covering around the nerve⁴ if the needle is beneath this layer a small volume 10–15 ml will be sufficient to obtain a spread of local anaesthetic around or close to the nerve.⁵

1–3 The main Indications are:

• In combination with femoral nerve block:

- Anaesthesia for leg, ankle and foot surgery with thigh tourniquet

• Well adapted to ambulatory surgery

• Post-operative analgesia

- After ankle or foot surgery

• In trauma situations

- Anaesthesia and Analgesia for leg, ankle and foot trauma.

2 – Ankle tourniquet with distal blocks for foot surgery.

Ankle blocks can be used only with an ankle tourniquet, the most often for middle and forefoot surgery.

Ankle blocks allows safe and long duration analgesia and anesthesia while providing quick mobilization.⁶

2–1 The innervation of the foot is provided by:⁷

- The terminal branch of the femoral nerve: the saphenous nerve

- The two terminal branches of the sciatic nerve

• Common peroneal nerve

- The common peroneal nerve divides into

• Deep peroneal nerve

• Superficial peroneal nerve

• Tibial nerve

- The tibial nerve innervates a large portion of the foot.

- At the popliteal fossa, a sensitive nerve branch emerges from the tibial nerve: the sural nerve

2–2 The main indication Indications⁸ are:

• Foot surgery without tourniquet

• Foot surgery with ankle tourniquet for short procedures

• Post-operative analgesia

• Complementary blocks in case of more proximal failure

Tibial nerve block Insert the needle at the outer posterior or anterior end of the ultrasound probe, and advance it parallel to the long axis of the probe in the same plane as the ultrasound beam in the direction of the tibial nerve which is usually adjacent to the tibial artery.

Inject 5–8 ml of local anaesthetic.

The tibial nerve block provides an anaesthesia of the plantar area of the foot.

Deep peroneal nerve block Insert the probe transversely on the anterior aspect of the tibia.

Identify the Extensor hallucis longus tendon medially, the Extensor digitorum longus tendon laterally and Anterior tibial artery lying at the anterior surface of the tibia.

Insert needle perpendicular to the skin in direction to the nerve lying just lateral or medial to the anterior tibial artery.

The Deep peroneal nerve block provides an anaesthesia to the bones of the dorsal part of the

Foot and a small cutaneous area between the first and second toes.

Superficial peroneal nerve • Position the probe on the lateral aspect of the lower leg proximal to the fibula. The superficial peroneal nerve lies between the extensor digitorum longus and peroneus brevis muscles just beneath the fascia lata.

• Inject 3–5 ml of local anesthetic surrounding or close to the nerve.

• The superficial peroneal nerve block provides an anaesthesia to the skin of the dorsal part of the foot, excluding the fifth toe and the first interdigital space

Sural nerve • The probe is positioned, on the posterolateral aspect of the Achille’s tendon. Identify the short saphenous vein lying superficially between the Achilles’ tendon and the peroneus brevis muscle.

The sural nerve block provides an anaesthesia to the lateral part of the dorsum of the foot including the fifth, fourth and often the third digit.

Saphenous nerve Place the probe transversally just proximal and anterior to the medial malleolus, then identify the great saphenous vein.

Inject 2to 3 ml of local anaesthetic on both sides of the saphenous vein.

• Anaesthesia of the medial part of the ankle and foot.⁸

2–4 Local anaesthetics solution⁹:

- Short procedure:

• Lidocaine 1% +/- epinephrine

• Mepivacaine 1%+/- epinephrine

- Long procedure or for postoperative analgesia :

• Bupivacaine or L-Bupivacaine 0,25%+/- epinephrine

• Ropivacaine 0,375%

Conclusion Proximal blocks are highly efficient when using a thigh tourniquet. They are appropriate and convenient technique for Ankle and foot Ambulatory surgery.

Ankle blocks are very selective nerve blocks, with low risk technique[1] . They must be used ‘’in combination’’ for total anaesthesia of the foot. These nerves are easily identified and blocked with a low dose of local anesthetics and lead to rapid patient mobilization and discharge.

References

1. Kahn RL, et al. The Incidence of Complications Is Low Following Foot and Ankle Surgery for Which Peripheral Nerve Blocks Are Used for Postoperative Pain Management. HSS J 2018; 14(2):134–142.

2. Gianakos AL, et al. Combination Lower Extremity Nerve Blocks and Their Effect on Postoperative Pain and Opioid Consumption: A Systematic Review. J Foot Ankle Surg,2021; 60(1):121–131.

3. Bjorn S, et al. The Importance of the Saphenous Nerve Block for Analgesia Following Major Ankle Surgery: A Randomized, Controlled, Double-Blind Study. Reg Anesth Pain Med,2018; 43(5):474–479.

4. Karmakar MK, et al. Ultrasound-guided subparaneural popliteal sciatic nerve block: there is more to it than meets the eyes. Reg Anesth Pain Med 2021; 46(3):268–275.

5. Techasuk W, et al. Minimum effective volume of combined lidocaine-bupivacaine for analgesic subparaneural popliteal sciatic nerve block. Reg Anesth Pain Med 2014; 39(2):108–11.

6. Korwin-Kochanowska K, et al. PROSPECT guideline for hallux valgus repair surgery: a systematic review and procedure-specific postoperative pain management recommendations. Reg Anesth Pain Med 2020; 45(9):702–708.

7. Delbos A, et al. Ultrasound-guided ankle block. History revisited. Best Pract Res Clin Anaesthesiol 2019; 33(1):79–93.

8. Lopez AM, et al. Ultrasound-guided ankle block for forefoot surgery: the contribution of the saphenous nerve. Reg Anesth Pain Med 2012; 37(5):554–7.

9. Marty P, et al. Perineural Versus Systemic Dexamethasone in Front-Foot Surgery Under Ankle Block: A Randomized Double-Blind Study. Reg Anesth Pain Med 2018; 43(7):732–737.