What is the adverse effect of a common peroneal nerve (CPN) block?

Common Peroneal Nerve Block Adverse Effects

The primary adverse effect of a common peroneal nerve block is foot drop, which causes weakness or paralysis of ankle dorsiflexion and eversion, resulting in gait difficulties and increased risk of falls. 1

Anatomical Considerations

• The common peroneal nerve is particularly vulnerable to injury due to its superficial course as it wraps around the fibular head 2
• The nerve is commonly located just medial to the biceps femoris tendon and near the fibular head, making it susceptible to compression 1
• Pressure near the fibular head from contact with a hard surface or rigid support significantly increases the risk of peroneal neuropathy 1

Primary Adverse Effects

• Motor Deficits:

  • Weakness or paralysis of the tibialis anterior and extensor hallucis longus muscles 3
  • Inability to dorsiflex the ankle (foot drop) 2
  • Inability to evert the foot 3
  • Steppage gait pattern to avoid dragging toes during walking 4

• Sensory Deficits:

  • Decreased sensation or numbness in the distribution of the common peroneal nerve 3
  • Hypoesthesia in the first web space between the great and second toes 4
  • Potential paresthesia in the dorsum of the foot 5

Clinical Impact on Patient Function

• Significant gait difficulties due to foot drop 2
• Increased risk of falls due to inability to clear the foot during walking 2
• Functional limitations in daily activities 6
• Potential for long-term disability if not properly managed 3

Risk Factors and Prevention

• Prolonged pressure on the peroneal nerve at both hip and knee joints can increase risk 1
• Specific padding to prevent contact of the peroneal nerve with hard surfaces may decrease the risk of peroneal neuropathy 1
• Care or avoidance of the fibular head region is recommended when performing procedures near this area 1
• Inappropriate use of padding (e.g., padding too tight) may paradoxically increase the risk of neuropathy 1

Management Considerations

• Early recognition of symptoms is crucial for optimal outcomes 4
• Conservative management with ankle-foot orthosis (AFO) may be effective for temporary nerve blocks 4
• Monitoring for recovery of motor function, particularly in the tibialis anterior and extensor hallucis longus 3
• Surgical decompression may be necessary in cases of persistent deficits 5

Special Considerations in Medical Procedures

• When planning procedures near the common peroneal nerve, care should be taken to avoid compression at the fibular head 1
• Prolonged static positioning during procedures increases risk of compression injury 4
• Thorough testing for block success is encouraged to prevent complications 1
• Positioning should be carefully monitored throughout procedures involving the lower extremity 7

Common Pitfalls

• Failure to recognize early symptoms of peroneal nerve compression 5
• Relying solely on electrodiagnostic studies, as some cases of complete foot drop may present with normal studies 5
• Inadequate padding or protection of the fibular head region during procedures 1
• Overlooking the risk of peroneal nerve injury during positioning for unrelated procedures 3