This is a stellate fracture, also called “spider web”, because of the several circular fractures connected to each other with linear fracture radiating from the centre, which may or not be depressed.
They are caused by heavy blunt weapons with large striking surface. In this case the fracture was caused by the sledge hammer you see on your right.
Beautifully designed traditional Japanese Kanzashi hair ornaments by Sakae
DAMN FRANKIE FOSTER IS 30