Head trauma tops the list of severe injuries involving the use of electric scooters — injuries that in many cases could have been prevented with the use of a helmet, according to an investigation by the Centers for Disease Control and Prevention and the Austin public health department.

Almost half of the riders identified in the study had a severe injury, such as a broken leg, and half reported that a surface condition such as a pothole or crack in the street may have contributed to their injury, according to the report, released Thursday. Fewer than 1 percent of those injured were wearing a helmet.

The investigation, the first from the CDC into scooter use, gathered information from people treated at Austin hospitals last fall for injuries associated with the use of rental scooters. It comes amid spreading reports of related injuries and deaths in cities including the District, Los Angeles and Dallas; it also follows recent news of scooter failures and breakdowns.