The Ankle block allows for anesthesia of the entire foot below the malleoli. In general the ankle block provides excellent anesthesia for any surgery to the foot and has the advantage of not inhibiting any early ambulation.
Anatomy
There are FIVE peripheral Nerves supplying the foot below the ankle. Due to some cross over generally all 5 need to be blocked to achieve successful anesthesia for surgery of the foot.
These five nerves and the areas they block are:
- Saphenous nerve (medial aspect of foot)
- Sural nerve (postero lateral aspect of foot)
- Superfical Peroneal nerve (dorsum of toes and foot)
- Deep Peroneal nerve (are between great toe and 2nd toe)
- Posterior Tibial nerve (sole of foot)
The saphenous nerve is a branch of the femoral nerve while the remainder are branches of the sciatic nerve.
Coverage achieved by the block:
When all five nerves are blocked this technique can be used for any surgery of the foot below the malleoli.
Indications
Any surgery below the level of the ankle at the malleoli, with foot and forefoot surgery the most optimal (for guaranteed coverage).
Block Technique
Corresponding to the five nerves there are five injection sites that need to be addressed in a circumferential manner starting medially and posteriorly behind the medial malleolus of the ankle.
The tibial and deep peroneal supply deep structures and have to be blocked deep to the fascia of the ankle. The others supply skin and superficial structures and can be blocked superficially.
Generally a total of 25ml of local anesthetic solution is used preferably 0.25% or 0.5% bupivacaine or ropivacaine for a longer lasting block. This choice means block onset time may take up 20 mins to be effective. Lidocaine can be used for a shorter block and epinephrine can be added to extend the block duration.
Due to the tight facial layers with limited room for expansion, this is a relatively painful block (for an awake patient). So in general awake blocks generally NOT recommended; asleep or sedated is preferred. While some ultrasound optimization is possible when blocking the peroneal nerve using the other nerves are relatively superficial (i.e more field blocks) and are unlikely to be improved using ultrasound by most users.
Due to multiple injections sites a continuous technique is not a realistic option.
Duration
The block will give anesthesia for up to 2 hours and analgesia generally for 6 to 24 hours.
Important contraindications and side effects
Contraindications are the same as with most blocks. These include patient refusal, site infection, and allergies to medications, infection, hematoma or significant bruising at the site or pre-existing nerve injuries. A relative contraindication is an awake patient.
Who do I contact if I feel my patient could benefit from a regional anesthesia technique?
When booking OR cases, surgeons can enter requests for regional anesthesia. The Department of Anesthesia schedules experienced providers to perform these blocks in all ORs. For regional anesthesia in inpatients reach out to the Acute Pain Service that covers your campus.
Please see the link for the pain team consult service:
https://anesthesia.ucsf.edu/divisions/pain-medicine - for-providers--request-consult-or-refer-a-patient