Adjacent Segment Disease (ASD), sometimes called Accelerated Adjacent Segment Degeneration, occurs after a spinal fusion surgery. Due to the fusion of multiple vertebrae, there are bio-mechanical changes to the way the spine functions; the area that is fused loses its ability to move properly. When this occurs, the vertebrae and their joints, immediately above and below the fusion will degenerate at an accelerated rate due to an increase in stress on the joints and spinal discs. So let's back up for a minute. Common causes for spinal fusion surgery included degenerative, bulging, or herniated discs which creates stenosis of the spine and puts pressure on nerves causing nerve pain, numbness/tingling, and loss of function in the extremities. Usually, these types of disc issues are caused by excessive stress on the spinal discs and joints over a long period of time which slowly weakens the discs until they collapse. So once a spinal fusion has been done to "correct" the ...