In forceful inversion of foot, fracture of the tuberosity of 5th metatarsal is due to pull exerted by which tendon:
First, the 5th metatarsal has a tuberosity that's part of the lateral foot. The tuberosity is the attachment site for certain tendons. When the foot is forcefully inverted, certain muscles are activated. The peroneus brevis tendon runs along the lateral side and inserts on the base of the 5th metatarsal. During inversion, the peroneus brevis is supposed to evert the foot, but if the inversion is too strong, maybe the tendon's pull could cause a fracture. Wait, but inversion is the opposite of eversion. So when the foot is forcefully inverted, the peroneus brevis might be under tension trying to correct the inversion, leading to a stress fracture at its insertion.
Wait, another possibility is the peroneus longus. But peroneus longus inserts on the base of the 1st metatarsal and the medial cuneiform. So not the 5th. So peroneus brevis is more likely here. The tuberosity of the 5th metatarsal is where the peroneus brevis tendon attaches. So during inversion, the peroneus brevis contracts to evert the foot, but if inversion is too forceful, the opposing force could cause a avulsion fracture of the tuberosity.
As for the other options, maybe the extensor digitorum longus? That inserts on the dorsal surfaces of the 2nd to 5th metatarsals. But during inversion, the main action is not on the 5th metatarsal's tuberosity. The tibialis anterior is more involved in dorsiflexion and inversion, but its insertion is on the medial side. The tibialis posterior is a plantarflexor and inverter, but inserts on the navicular. So those are less likely. The peroneus brevis is the key here.
So the correct answer should be peroneus brevis. Let me check again. The peroneus brevis tendon runs behind the lateral malleolus, inserts on the 5th metatarsal base. Forceful inversion would cause the peroneus brevis to contract, pulling on the tuberosity, leading to avulsion fracture. Yes, that makes sense. So the answer is peroneus brevis.
**Core Concept**
Fractures of the 5th metatarsal tuberosity during forceful foot inversion are caused by avulsion due to the **peroneus brevis tendon**, which inserts at the base of the 5th metatarsal. This injury is a classic example of **avulsion fractures** from tendon traction during extreme joint motion.
**Why the Correct Answer is Right**
The **peroneus brevis tendon** inserts on the base of the 5th metatarsal. During forceful foot inversion, the peroneus brevis contracts to oppose the movement, creating a strong pull on its insertion site. This generates a lever arm that can avulse the tuberosity, especially if the force exceeds bone strength. The mechanism is similar to