A patient with posterior dislocation of the hip develops footdrop and loss of sensation over the dorsum of the foot. Which nerve is injured and by what mechanism?

• A Common peroneal nerve stretched over the fibular neck
• B Sciatic nerve — common peroneal division injured at the hip ✓
• C Deep peroneal nerve compressed in the anterior compartment
• D Tibial nerve compressed in the popliteal fossa

Explanation

Posterior hip dislocation can directly injure the sciatic nerve, and the common peroneal division (L4-S1) is more susceptible than the tibial division because the peroneal fibers are positioned more superiorly and laterally in the sciatic nerve, making them vulnerable to stretch during posterior dislocation. This produces footdrop (loss of dorsiflexion and toe extension) and sensory loss over the dorsum of foot and lateral leg. Isolated common peroneal nerve injury at the fibular neck (from another mechanism such as casts or cross-legged sitting) produces the same clinical picture.

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

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Written and medically reviewed by the StethoPrep medical team.