Type B1 is a monosegmental bony posterior tension band injury.
There is complete osseous failure of the posterior tension band at one level that extends into the vertebral body. These are also known as seatbelt or "Chance" fractures (named after George Quentin Chance, a British radiologist who first described it in 1948).
This injury can be associated with any A-type fracture (vertebral body).
CT/radiograph images are examined to determine the fracture type.