Question

Which nerve will be commonly involved if the injury occurs at the marked levels?

• A. L4
• B. L5
• C. L2
• D. L3

Hint:

L5 nerve root lesions are often associated with foot drop and weakness in the dorsiflexion of the foot, and they are common in lumbar spine injuries.

Answer 1

The Correct Option is B

In the context of the question regarding which nerve is commonly involved if an injury occurs at certain spinal levels, it is important to understand the relationship between spinal levels and the nerves they affect.

The human spinal cord is divided into segments that correspond to vertebrae. Each segment is associated with a pair of spinal nerves, which are named after the vertebral level they exit from. The spinal nerves control sensorimotor functions by innervating different parts of the body, including muscles and skin.

For the specific spinal segment in question:

• L2 - Innervates muscles that flex the hip.
• L3 - Innervates muscles that control the knee extension.
• L4 - Affects the quadriceps and is involved in knee-jerk reflex.
• L5 - Affects muscles responsible for dorsiflexion, a movement that raises the foot upwards.

In clinical practice, L5 is commonly associated with injuries due to its position and the frequency with which it bears weight and bends. An injury at L5 can affect the extensor muscles which are crucial for foot movements.

Therefore, the nerve commonly affected by an injury at the marked levels is:

• Correct Answer: L5