Fractures of the shaft of the tibia are due to direct trauma. This particular fracture is spiral in nature. More comminuted fractures of the proximal tibia may compromise blood supply of the popliteal artery, and angiography may be considered.
AP radiograph of the tibia and fibula. There is a spiral fracture of the tibia. 
Lateral radiograph of the tibia and fibula. This demonstrates a spiral fracture of the tibia.