LKnative – Ankle block

Indications

The indications of an ultrasound guided ankle block is forefoot surgery as an alternative to a combined popliteal sciatic and midthigh saphenous nerve blockade

It is not indicated for surgical anaesthesia if a tourniquet is applied proximal to the ankle level

All five nerves innervating the foot have to be anaesthetized which can be painful in the awake patient

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Anatomy: The trajectory of the sural nerve

The sural nerve is a sensory nerve made of the fusion of the medial sural cutaneous nerve from the tibial nerve and of a communicating branch from the lateral sural cutaneous nerve from the common fibular nerve

The two sural cutaneous nerves pierce the deep fascia – together with the short saphenous vein – before the fusion that makes the sural nerve

The sural nerve descends posterior to the lateral malleolus together with the short saphenous vein

The sural nerve innervates the postero-lateral part of the skin cover of the ankle and supply calcaneal branches that innervate the lateral heel and lateral dorsal cutaneous nerves that innervate the lateral margin of the foot