The sural nerve can be blocked as part of the ankle block with ultrasound guidance posterior to the lateral malleolus adjacent to the short saphenous vein
Sural nerve (yellow shadow), short saphenous vein (larger blue shadow), venous branch (smaller blue shadow), peroneus brevis (white asterix), tendon of peroneus longus (blue arrow), soleus (red asterix), tendon of achilles (yellow arrow)