Waddell's triad is a pattern of injury seen in pedestrian children who are struck by motor vehicles. The triad comprises:

• fractured femoral shaft
  Body of femur
  The body of the femur , almost cylindrical in form, is a little broader above than in the center, broadest and somewhat flattened from before backward below...
  
  
• intra-thoracic
  Chest trauma
  Chest trauma is a serious injury of the chest. Thoracic trauma is a common cause of significant disability and mortality, the leading cause of death from physical trauma after head and spinal cord injury. Blunt thoracic injuries are the primary or a contributing cause of about a quarter of all...
  
   or intra-abdominal injuries
  Abdominal trauma
  Abdominal trauma is an injury to the abdomen. It may be blunt or penetrating and may involve damage to the abdominal organs. Signs and symptoms include abdominal pain, tenderness, rigidity, and bruising of the external abdomen. Abdominal trauma presents a risk of severe blood loss and infection...
  
  
• contralateral head injury
  Head injury
  Head injury refers to trauma of the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in medical literature....
  
  

The mechanism of injury is an initial impact causing injury to the femur on one side (bumper injury) and the torso on the same side (fender

Fender (vehicle)

Fender is the US English term for the part of an automobile, motorcycle or other vehicle body that frames a wheel well . Its primary purpose is to prevent sand, mud, rocks, liquids, and other road spray from being thrown into the air by the rotating tire. Fenders are typically rigid and can be...

 or hood

Hood (vehicle)

The hood or bonnet is the hinged cover over the engine of motor vehicles that allows access to the engine compartment for maintenance and repair. In British terminology, hood refers to a fabric cover over the passenger compartment of the car...

), following which the child is thrown, striking the head on the ground or another object and sustaining injury to the opposite side of the head. In countries where cars drive on the right, pedestrians tend to be struck on the left, causing left femur fractures, injuries to the left chest or spleen

Spleen

The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...

, and right sided head injuries.

Although this injury pattern may not be common, it is used to emphasize the point that children involved in high energy impacts should not be assumed to have isolated injuries.