Which action is spared in isolated deep peroneal nerve injury?

Which action is spared in isolated deep peroneal nerve injury?

• A. Eversion of the foot
• B. Dorsiflexion
• C. Toe extension
• D. Plantarflexion

Answer: (D)

When a deep peroneal nerve injury is isolated, the muscles it supplies in the anterior compartment are affected. Those muscles enable dorsiflexion of the foot and extension of the toes (tibialis anterior, extensor digitorum longus, extensor hallucis longus). Plantarflexion, on the other hand, is mainly carried out by the posterior compartment through the tibial nerve (gastrocnemius and soleus), so it remains intact. Eversion is primarily controlled by the superficial peroneal nerve, which is not affected in an isolated deep peroneal injury, so it can also be preserved. Therefore, plantarflexion is the action that stays spared.

When a deep peroneal nerve injury is isolated, the muscles it supplies in the anterior compartment are affected. Those muscles enable dorsiflexion of the foot and extension of the toes (tibialis anterior, extensor digitorum longus, extensor hallucis longus). Plantarflexion, on the other hand, is mainly carried out by the posterior compartment through the tibial nerve (gastrocnemius and soleus), so it remains intact. Eversion is primarily controlled by the superficial peroneal nerve, which is not affected in an isolated deep peroneal injury, so it can also be preserved. Therefore, plantarflexion is the action that stays spared.