When vertebral bones are weak or brittle from osteoporosis they can collapse. This is called a vertebral compression fracture. If the bone doesn't heal or doesn't get enough blood supply, a space or pocket occurs. This air-filled cleft inside the vertebral body can be seen on X-ray and MRI.
Special X-rays show the cleft gives the bone motion where there shouldn't be any movement. The best way to treat this is to inject cement into the bone to fill up the space and hold the bone together. Pain relief is immediate because the cement stops this unnatural motion.