What defines an avulsion fracture?

An avulsion fracture is specifically characterized by the separation of a bone fragment at the site of attachment of a ligament or tendon. This type of fracture typically occurs when a strong force is applied to a tendon or ligament that is attached to a bone, causing a small piece of the bone to be pulled away. This is commonly seen in sports injuries, where quick movements or sudden changes in direction can lead to this type of injury.

In contrast, the other descriptions refer to different types of fractures. A complete break at the midshaft indicates a simple fracture situation unrelated to the connective tissues' pull. A fracture through a joint causing instability points to a more complex fracture that typically would affect the joint's integrity and function. An intra-articular fracture involves the joint itself, which could lead to dislocation, but does not describe the mechanism of an avulsion fracture where the focus is on the traction forces from tendons and ligaments.