What motor finding would support peroneal nerve injury at the fibular neck?

What motor finding would support peroneal nerve injury at the fibular neck?

• A. Plantarflexion weakness
• B. Foot drop (weak dorsiflexion)
• C. Inversion weakness
• D. Great toe extension weakness

Answer: (B)

Injury to the fibular neck damages the common peroneal nerve as it wraps around that bone, affecting its branches. The deep branch runs to the dorsiflexors of the foot (like tibialis anterior) and toe extensors, so loss here causes weakness of dorsiflexion. When dorsiflexion is weak, the foot cannot clear the ground during walking, producing a classic foot drop. The plantarflexors and invertors, supplied mainly by the tibial nerve, are usually intact, so plantarflexion and inversion are preserved. Great toe extension can be affected if the deep peroneal branch is involved, but the hallmark motor deficit from a fibular neck injury is dorsiflexion weakness leading to foot drop.

Injury to the fibular neck damages the common peroneal nerve as it wraps around that bone, affecting its branches. The deep branch runs to the dorsiflexors of the foot (like tibialis anterior) and toe extensors, so loss here causes weakness of dorsiflexion. When dorsiflexion is weak, the foot cannot clear the ground during walking, producing a classic foot drop. The plantarflexors and invertors, supplied mainly by the tibial nerve, are usually intact, so plantarflexion and inversion are preserved. Great toe extension can be affected if the deep peroneal branch is involved, but the hallmark motor deficit from a fibular neck injury is dorsiflexion weakness leading to foot drop.