When there is a loss of the normal alignment in the spine, and the spine bends forward, the condition is called kyphosis. Kyphosis is when your lower back curves the wrong way. If that curve becomes reversed, or bent-over, either by a disease or a surgical procedure, it has the effect of pushing your upper spine forward. When it's bad enough to cause pain and functional limitations, you may need treatment. In the lumbar spine, it is called "flat-back syndrome", but it can also occur in the neck and thoracic spine.
Line Drawing Animated Video of Kyphosis