Which of the following are features of common peroneal nerve injury? 1. Inversion inability 2. Loss of sensation of sole 3. Foot drop 4. Loss of extension of great toe 5. Seen in fibular neck fracture
## Core Concept
The common peroneal nerve (also known as the common fibular nerve) is a nerve in the lower extremity that innervates muscles involved in ankle and toe movements. Injury to this nerve results in specific motor and sensory deficits. Understanding the anatomy and function of the common peroneal nerve is crucial for diagnosing and managing its injuries.
## Why the Correct Answer is Right
The common peroneal nerve injury leads to:
- **Foot drop** (3) due to weakness of the muscles responsible for ankle dorsiflexion, primarily the tibialis anterior muscle.
- **Loss of extension of the great toe** (4) because the extensor hallucis longus muscle, which is responsible for this action, is innervated by the deep peroneal nerve, a branch of the common peroneal nerve.
- The injury is **seen in fibular neck fracture** (5) because the common peroneal nerve wraps around the lateral aspect of the fibular neck, making it susceptible to injury in this area.
## Why Each Wrong Option is Incorrect
- **Option A: Inversion inability** (1) - Inversion of the foot is primarily controlled by muscles innervated by the tibial nerve (e.g., tibialis posterior). Therefore, inability to invert is not a feature of common peroneal nerve injury.
- **Option B: Loss of sensation of sole** (2) - The sensation to the sole of the foot is provided by the medial and lateral plantar nerves, which are branches of the posterior tibial nerve, not the common peroneal nerve.
## Clinical Pearl / High-Yield Fact
A key clinical feature of common peroneal nerve injury is **foot drop**, which often leads to a steppage gait to compensate for the inability to dorsiflex the foot. This condition can result from various causes, including trauma (like fibular neck fractures), compression (as in peroneal nerve palsy), or systemic conditions like diabetes.
## Correct Answer: C.