Which fracture involves more than three fragments at the site and is caused by a hard blow or fall?

The choice of a comminuted fracture is accurate because this type of fracture is characterized by the bone being shattered into multiple fragments, often more than three. This condition typically arises from high-impact trauma, such as a significant blow or fall, which applies excessive force to the bone, causing it to break into numerous pieces.

In contrast, a transverse fracture involves a straight horizontal break across the bone, while a blowout fracture results from an impact that displaces a fragment of bone from the orbital cavity, commonly impacting the eye area. An avulsion fracture occurs when a fragment of bone is pulled away by a tendon or ligament, indicating different mechanisms of injury. These distinctions emphasize that only the comminuted fracture accurately represents the described injury's characteristics of fragmentation and the cause involved.