Chapter 39. Ankle Block

Foot anesthesia is readily accomplished by blocking the five peripheral nerves that innervate the area by means of local anesthetic deposition either slightly proximal or distal to the malleoli.1–5 This technique is easily learned and simple to perform, using straightforward visual and palpable anatomic landmarks. It does not require special equipment, paresthesia elicitation, nerve stimulation, special positioning, or patient cooperation.1–5

Ankle block can be used for all types of foot surgery and is safe and reliable, with success rates of 89–100%.2,3,5–9

Because it does not cause motor blockade of the leg, patients are able to ambulate with crutches immediately after surgery and can be discharged home without recovery.4 With the use of long-acting local anesthetics such as bupivacaine or ropivacaine, prolonged postoperative analgesia of up to 17 hours or longer may be accomplished.6,9

Indications & Contraindications

All types of foot surgery can be carried out with the patient under ankle block, including hallux valgus repair, forefoot reconstruction, arthroplasty, osteotomy, and amputation.1–10 Ankle block can also provide analgesia for fracture and soft tissue injuries11 and gouty arthritis.12 Moreover, it can be used for diagnostic and therapeutic purposes with spastic talipes equinovarus13 and sympathetically mediated pain.14 Because motor block of the leg is avoided, ankle block may be preferable to sciatic/femoral (saphenous) nerve block for outpatient forefoot surgery.15

Ankle block should be avoided whenever there is infection, edema, burn, soft tissue trauma, or distorted anatomy with scarring in the area of block placement. Ankle block should also be avoided in a patient with vascular compromise due to compartment syndrome. In patients with severe coagulopathy, the risk of hematoma is increased, and if ankle block is performed, a more distal approach such as the midtarsal approach, in which blood vessels are more superficial and compressible, may be preferable.

Pertinent Anatomy

The foot is supplied by five nerves (Figures 39–1 and 39–2). The medial aspect is innervated by the saphenous nerve, a terminal branch of the femoral nerve (Figure 39–3). The rest of the foot is innervated by branches of the sciatic nerve:

• The lateral aspect is innervated by the sural nerve arising from the tibial and communicating superficial peroneal branches (Figure 39–4).
• The deep plantar structures, muscles and sole of the foot are innervated by the posterior tibial nerve, arising from the tibial branch (Figure 39–5).
• The dorsum of the foot is innervated by the superficial peroneal nerve, arising from the ...