A barefoot child steps on some glass on the sole of his foot and complaints of numbness of the small toe. Which nerve has he most likely injured?
First, I need to recall the nerves that innervate the foot, specifically the sole and the toes. The foot has both superficial and deep nerves. The main nerves involved in sensation here would be the medial plantar nerve, lateral plantar nerve, and maybe the sural nerve, but the sural is more on the lateral side of the foot and ankle. The medial and lateral plantar nerves are branches of the tibial nerve, which splits into those two. The medial plantar nerve primarily supplies the medial part of the sole, including the first three toes. The lateral plantar nerve supplies the lateral part of the sole, including the fourth and fifth toes. The small toe is the fifth toe, so numbness there would point to the lateral plantar nerve. Wait, but the lateral plantar nerve is more for the lateral side. Wait, maybe I'm mixing this up. Let me think again. The medial plantar nerve is responsible for the medial part of the sole and the first three toes. The lateral plantar nerve would handle the lateral part, including the fourth and fifth toes. So if the small toe (fifth) is numb, it's the lateral plantar nerve. But wait, the lateral plantar nerve also contributes to the plantar aspect of the foot. So the injury here would be the lateral plantar nerve. But I should also consider other possibilities. The superficial peroneal nerve is more on the dorsum of the foot and supplies the lateral dorsum, so not involved here. The sural nerve is sensory for the lateral ankle and foot. The saphenous nerve is medial side of the leg and foot. So the key here is the plantar nerves. The medial plantar nerve is responsible for the first three toes and the medial sole. The lateral plantar nerve is for the lateral sole and the fourth and fifth toes. Therefore, injury to the lateral plantar nerve would cause numbness in the fifth toe. Therefore, the correct answer is the lateral plantar nerve. The options would have that as one of the choices. The other options like the medial plantar, sural, or superficial peroneal would not cause numbness in the small toe. So the answer is lateral plantar nerve.
**Core Concept**
This question tests knowledge of foot nerve innervation, specifically the **lateral plantar nerve** and its role in sensory supply to the lateral plantar foot and fifth toe. The lateral plantar nerve is a terminal branch of the tibial nerve within the tarsal tunnel.
**Why the Correct Answer is Right**
The **lateral plantar nerve** innervates the **lateral plantar skin of the foot** and the **lateral three and a half toes**, including the **fifth toe (small toe)**. Injury to this nerve, often via trauma to the sole (e.g., stepping on glass), disrupts sensory function in its territory. The nerve runs deep in the sole, making it vulnerable to sharp objects piercing the plantar surface.
**Why Each Wrong Option is Incorrect**
**Option A:** *Medial plantar nerve* supplies the **medial three and a half toes** and medial sole; numbness