What regional techniques can cause foot drop?

Regional Techniques That Can Cause Foot Drop

Dense neuraxial or peripheral nerve blocks that result in long-duration blocks significantly exceeding the duration of surgery should be avoided due to their potential to cause foot drop and mask symptoms of acute compartment syndrome. 1

Common Regional Techniques Associated with Foot Drop

• Popliteal sciatic nerve block is a significant cause of foot drop as it blocks both tibial and common peroneal nerve components, leading to complete motor blockade of ankle dorsiflexion 2, 3
• Proximal sciatic nerve blocks performed above the bifurcation can cause complete foot drop by affecting both tibial and peroneal components 3
• Dense epidural or spinal anesthesia with high concentrations of local anesthetics can cause temporary foot drop during the duration of the block 1
• Regional techniques using high concentrations of local anesthetics or adjuncts that prolong block duration increase the risk of prolonged foot drop 1

Risk Factors for Developing Foot Drop After Regional Anesthesia

• Pre-existing peripheral neuropathies increase the risk of developing foot drop after peripheral nerve blocks 2
• Use of vasoconstrictive local anesthetics (like ropivacaine) may contribute to neuronal ischemia in patients with pre-existing nerve compromise 2
• Advanced age and comorbidities affecting peripheral nerves (diabetes, alcoholism) increase susceptibility to nerve injury 2, 4
• High-volume injections around nerves may increase pressure and contribute to nerve injury 3

Safer Alternatives to Prevent Foot Drop

• Selective tibial nerve block in the popliteal fossa instead of complete sciatic nerve block provides effective analgesia without causing foot drop 3
• Using lower concentrations of local anesthetics (bupivacaine or ropivacaine 0.1-0.25% for single shot and 0.1% for continuous nerve blocks) reduces the risk of dense motor blockade 1
• Avoiding adjuncts to local anesthetics that increase block density and duration helps preserve motor function 1
• Single-shot or continuous peripheral nerve blocks with lower concentrations of local anesthetic without adjuncts maintain some sensory and motor function, allowing for better monitoring 1

Monitoring and Management

• Patients receiving regional anesthesia should be monitored for signs of foot drop during and after the procedure 1, 5
• Early detection of foot drop is essential to differentiate between block-related temporary weakness and surgical complications or acute compartment syndrome 5
• For patients with prolonged foot drop after regional anesthesia, ankle-foot orthoses can help with ambulation while awaiting recovery 4, 6
• Physical therapy and nerve stimulation may be beneficial for patients with persistent foot drop after regional anesthesia 6

Special Considerations

• In patients at risk for acute compartment syndrome, dense blocks that mask pain should be avoided as pain is a cardinal symptom for early diagnosis 1
• Military experience has shown that continuous peripheral nerve analgesia using low-dose local anesthetic solutions can provide analgesia while preserving some sensory and motor function, allowing identification of breakthrough pain 1
• In pediatric patients, low concentrations of local anesthetic can be used safely for single-shot and continuous nerve blocks with proper monitoring systems in place 1