When is a fracture considered impacted?

A fracture is considered impacted when the ends of the broken bone are driven into each other. This typically occurs during high-energy injuries, such as falls or collisions, where one part of the bone is compressed against another. This type of fracture can affect the alignment of the bone and may require special consideration during treatment to ensure proper healing.

The presence of three or more fragments pertains to a comminuted fracture, which is a different type of fracture altogether. A fracture that splits along its length is known as a longitudinal fracture, which again distinguishes it from an impacted fracture. A clean fracture with sharp edges is often referred to as a simple or closed fracture, indicating a fracture without complications such as fragment separation or impaction. Therefore, the definition and mechanism involved in an impacted fracture specifically align with the description provided in the correct answer.