Unusual mechanism of Chance fracture in an adult.

Flexion-distraction injuries of the upper lumbar spine typically occur in case of a head-on motor vehicle collision, while wearing a lap seat belt without shoulder strap. According to Smith and Kaufer the axis of flexion is situated at the point of contact of the belt with the abdominal wall. This results in a horizontal separation of the anterior, middle and posterior columns. The lesion is called a Chance fracture when it involves primarily bone, rather than ligaments. However, a Chance fracture can happen in unbelted persons: the present case concerns a 30-year-old man who fell from a height.