Which type of fracture involves a cracked bone but not a complete break?

A greenstick fracture is characterized by a cracked bone that does not completely break through. This type of fracture is most commonly seen in children, whose bones are still pliable and softer than adult bones. The greenstick fracture behaves similarly to bending a young tree branch; it bends and partially breaks, instead of snapping completely in two. This is why the greenstick fracture is the correct answer, as it specifically describes an incomplete fracture.

Comminuted fractures involve the bone being shattered into multiple pieces, which is far more serious than a simple crack. Transversal fractures are those that run perpendicular across the bone and typically indicate a complete break. Avulsion fractures occur when a fragment of bone is pulled off by a tendon or ligament, again representing a different kind of injury than a simple crack without a full break. Thus, none of these other types represent the cracked but unbroken state of a greenstick fracture.