A 30-year-old man sustains a fracture of the neck of the fibula in a football injury. Over the next few days he develops foot drop and loss of sensation over the lateral aspect of the leg and the dorsum of the foot. Which of the following muscles will retain normal power?

• A Peroneus longus
• B Tibialis posterior ✓
• C Peroneus brevis
• D Extensor digitorum longus

Explanation

The patient has a common peroneal nerve injury at the fibular neck, causing paralysis of both the superficial peroneal branch (peroneus longus, peroneus brevis) and the deep peroneal branch (extensor digitorum longus, extensor hallucis longus, tibialis anterior). Tibialis posterior is innervated by the tibial nerve, not the common peroneal nerve, so its power is preserved. The most tempting distractor is extensor digitorum longus, which students sometimes assume is spared because the deficit is described as foot drop alone.

Reference: Snell's Clinical Anatomy, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.