Compressed spine. Frontal, three dimensional, coloured computed tomography (CT) scan of the sacrum of a patient with a compressed spine in the lumbar-sacral (lower) region. The lowest lumbar vertebra (pink block, upper centre) is touching the sacrum (below vertebra), a bone that joins to the coccyx (tail bone, lower centre) and the pelvis. In a healthy spine the vertebrae are separated by intervertebral disks. Compression may be caused by osteoporosis (brittle bone disease) or arthrosis, a degenerative joint disease. It can cause back pain and immobility.