What is the recommended anesthetic technique, including drug choice and volume, for a peripheral ankle block in an otherwise healthy adult undergoing percutaneous screw fixation of a talar neck fracture?

Ankle Block for Talar Neck Screw Fixation

Recommended Anesthetic Technique

For percutaneous screw fixation of a talar neck fracture in a healthy adult, perform an ultrasound-guided ankle block using lower concentration local anesthetic (0.25-0.5% bupivacaine or 0.5% ropivacaine) without adjuncts, blocking the tibial, deep peroneal, superficial peroneal, saphenous, and sural nerves with appropriate volumes for each nerve. 1

Specific Block Technique and Drug Selection

Primary Nerve Targets

For complete ankle anesthesia, you must block five nerves at the ankle level:

• Tibial nerve (posterior): 5-7 mL of 0.5% ropivacaine or 0.25-0.5% bupivacaine 1, 2
• Deep peroneal nerve (anterior): 3-5 mL of 0.5% ropivacaine or 0.25-0.5% bupivacaine 1
• Superficial peroneal nerve (anterolateral): 3-5 mL of 0.5% ropivacaine or 0.25-0.5% bupivacaine 1
• Saphenous nerve (anteromedial): 3-5 mL of 0.5% ropivacaine or 0.25-0.5% bupivacaine 1, 2
• Sural nerve (posterolateral): 3-5 mL of 0.5% ropivacaine or 0.25-0.5% bupivacaine 1

Volume and Concentration Rationale

The AnAnkle Trial demonstrated that ultrasound-guided peripheral nerve blocks with ropivacaine 7.5 mg/mL (0.75%) provided effective anesthesia for ankle fracture surgery, though this was performed more proximally at the popliteal level 2. However, for talar neck fractures specifically, you should use lower concentrations (0.5% ropivacaine or 0.25-0.5% bupivacaine) to avoid dense, long-duration blocks that could mask compartment syndrome 1.

Regional anesthesia is the preferred technique for all foot and ankle surgery over general anesthesia due to lower morbidity and complication rates 3.

Critical Safety Considerations for Talar Neck Fractures

Compartment Syndrome Risk Management

You must avoid dense blocks of long duration that significantly exceed surgical duration, as these may delay diagnosis of acute compartment syndrome (ACS) 4, 1. This is particularly important because:

• Talar neck fractures result from high-energy trauma and have tenuous blood supply 5, 6
• The Association of Anaesthetists specifically recommends against dense, long-duration blocks for lower leg trauma 4
• Single-shot blocks using lower concentrations without adjuncts are not associated with delays in ACS diagnosis when proper surveillance is implemented 4

Mandatory Post-Procedure Surveillance

You must implement the following monitoring protocol 4, 1:

• Staff trained in ACS recognition must perform observations at set frequencies using objective scoring charts 4
• Equipment for measuring intracompartmental pressure must be available on the ward 4
• Patient education and documented verbal consent regarding analgesic technique options and ACS symptoms 4, 1

Alternative Anesthetic Approach

If the surgeon objects to peripheral nerve blockade (though the anaesthetist has final authority on analgesic technique selection 4, 1), spinal anesthesia with low-dose hyperbaric bupivacaine (2 mL of 5 mg/mL = 10 mg total) is an acceptable alternative 2. The AnAnkle Trial used this exact regimen as their control group for ankle fracture surgery 2.

Multimodal Analgesia Protocol

Regardless of regional technique chosen, implement multimodal analgesia 4:

• Scheduled paracetamol and NSAIDs (not as-needed dosing) to reduce opioid requirements 4, 2
• Patient-controlled intravenous morphine for breakthrough pain 4, 2
• Avoid continuous catheter techniques for ankle blocks in this trauma setting due to ACS concerns 4

Common Pitfalls to Avoid

• Do NOT use adjuncts (epinephrine, clonidine, dexamethasone) with your local anesthetic, as these prolong block duration and increase ACS risk 1
• Do NOT use concentrations higher than 0.5% bupivacaine or equivalent for trauma cases 1
• Do NOT defer to surgeon preference if they request no regional anesthesia—the anaesthetist has final authority on analgesic technique 4, 1
• Do NOT perform the block without ensuring proper ACS surveillance protocols are in place postoperatively 4