What type of fracture does not involve any injury to the skin but involves a break in the bone?

The correct answer is a closed fracture. This type of fracture occurs when there is a break in the bone but the skin remains intact, meaning there is no open wound or exposure of the bone through the skin. Closed fractures can result from various causes, such as falls or direct impact, and while they may be painful and lead to swelling or bruising, they do not present the additional risks associated with open fractures, where the bone is exposed to the environment.

In contrast, a simple fracture is often considered synonymous with a closed fracture in some contexts, but it can sometimes refer more broadly to any break that doesn't involve fragmentation. A compound fracture, on the other hand, is characterized by an open wound where the fractured bone exits through the skin, creating a higher risk of infection and other complications. A stress fracture is a different type of injury, often resulting from repetitive force or overuse, and is usually not a complete break but rather a small crack in the bone.

Thus, the distinction of a closed fracture specifically emphasizes the integrity of the skin despite the bone being broken, which is what makes it the correct answer in this context.