After a tight below-knee plaster cast is applied for an ankle fracture, the patient develops severe foot pain, paresthesia along the dorsum of the foot and first web space, and weakness of foot dorsiflexion and toe extension. Which nerve is compressed?

• A Tibial nerve in the tarsal tunnel
• B Deep peroneal nerve in the anterior compartment
• C Superficial peroneal nerve in the lateral compartment
• D Common peroneal nerve at the fibular neck ✓

Explanation

The common peroneal nerve winds around the neck of the fibula (subcutaneously) and is vulnerable to compression by tight casts, tight bandages, or direct trauma at this site. Injury causes foot drop (loss of dorsiflexion and toe extension — deep peroneal branch), loss of foot eversion (superficial peroneal branch), and sensory loss over the lateral leg and dorsum of the foot. The key test is inability to dorsiflex the foot while inversion is partially preserved (tibialis anterior lost, tibialis posterior preserved). Deep peroneal nerve compression in the anterior compartment syndrome gives a more restricted sensory loss (only first web space).

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.