A compression fracture is a collapse of a vertebra. It may be due to trauma or due to a weakening of the vertebra (compare with burst fracture). This weakening is seen in patients with osteoporosis or osteogenesis imperfecta, lytic lesions from metastatic or primary tumors, or infection. In healthy patients it is most often seen in individuals suffering extreme vertical shocks, such as ejecting from an ejection seat.