Which type of fracture is least likely to occur from a single traumatic event?

A stress fracture is characterized by a small crack in a bone that develops gradually over time, typically due to repetitive forces or overuse. This type of fracture results from the accumulation of stress on the bone rather than from a single traumatic event. Individuals who engage in high-impact sports or activities that involve repetitive motion are more susceptible to these fractures, as the bone undergoes micro-damage that exceeds its ability to heal.

In contrast, a transverse fracture, impacted fracture, and spiral fracture generally result from acute trauma, such as falls, collisions, or twists that apply significant force to the bone all at once. These fractures occur suddenly and are generally the result of a single, clearly defined impact. Therefore, the nature of a stress fracture—developing from chronic stress rather than an acute injury—makes it the answer that aligns with the question of which type is least likely to occur from a single traumatic event.