I have heard of this, but would do some research before rushing into corrective surgery. It has to do with the column of fused spine and how it matches up with the non-fixed areas of the spine. Your sugery was 15 years ago, and the wear and tear at the junction is where the problem is. I refer you to the scoliosis research society web site (www.srs.org)and (www.texasback.com) for the Texas Back Institute. Flatback is a recently discovered syndrome, and I would do plenty of research from valid sources so that you can make a truly informed decision. You don't want to jump into surgery as major as this without knowing exactly what they are going to do. Then, if it is right, go for it.