The lamina is a part of the bone that forms an arch around the spinal cord. As we get older, degenerative changes can cause a narrowing of the opening for the spinal cord. This narrowing is referred to as stenosis.
Removing the lamina can increase the opening for the spinal canal and take the pressure off the spinal cord. This is one type of spinal cord decompression.
But removing the bone can cause the bones to collapse. Laminaplasty avoids this complication. Instead of removing the lamina, the bone is cut on one side to form a hinge joint. The bone swings out and away from the spinal canal.
When the laminae are cut on both sides of the spine, and the spinous process (back bone) is split down the middle, then the laminae can swing out like French doors.