12.3 Ankle Block

Question 1

a) List five nerves that can be blocked at ankle level for foot surgery. (5 marks)

Answer 1

1. Tibial
2. Deep Peroneal
3. Superficial Peroneal
4. Sural

5 Saphenous

Question 2

b) For each of these nerves, describe the sensory distribution within the foot. (5 marks)

Answer 2

Saphenous
Medial aspect of the foot and
ankle.

Tibial
Heel and plantar aspect of
the foot.

Deep peroneal
1st/2nd toe web space.

Superficial peroneal
Dorsum of the foot
excluding 1st/2nd toe web space.

Sural
Plantar aspect 4th/5th web
space and 5th toe, and
lateral aspect of the foot.

Question 3

c) Give the anatomical landmarks for an ankle block which aid correct placement of local anaesthesia for
each nerve. (5 marks)

Answer 3

Saphenous

Find saphenous vein anterior to medial
malleolus: inject subcutaneously from here
posteriorly as far as the Achilles tendon.

Tibial
Midway between medial malleolus and tip
of calcaneum, inject posteriorly to the
posterior tibial artery.

Deep peroneal
2–3 cm distal to the intermalleolar line,
palpate extensor hallucis longus.
Lateral to this is the dorsalis pedis artery: inject either side.

Superficial peroneal

Find tibial ridge, insert needle and direct
towards lateral malleolus raising a
subcutaneous wheal.

Sural

Infiltrate subcutaneously between lateral
malleolus and Achilles tendon.

Question 4

d) What are the advantages and disadvantages of an ankle block? (5 marks)

Answer 4

Advantages
1. Provides good postoperative analgesia.

2. May avoid general anaesthesia in high-risk
   patients.
3. Relatively simple technique with low risk of
   local anaesthetic toxicity.
4. Minimal motor block; can therefore be used
   for bilateral procedures.

Disadvantages
1. Can be uncomfortable to perform in awake or
unsedated patients.

2. Risk of vascular puncture causing haematoma.
   Saphenous vein particularly at risk.
3. If a tourniquet is to be used, does not alleviate
   tourniquet pain.