Stenosis is a filling of the spaces where the nerves, veins. and everything goes around the bones, and when this "stuff" fills in, it makes pain by pinching and cutting off flow. I guess you could also call it arthritis. When they fused my five vertebrae, they cleaned it out so there would be more room until it may grow back and fill in again, who knows? I don't know how to describe it all, so you would need a medical explanation of the surgery. They also put in a metal cage to hold the fused bones in place. I think it is a miracle that I can bend over and touch the floor and I can walk pretty well. I was told the stenosis could grow back some or my upper spine could be affected. They made more space for the nerves to function. It was dangerous surgery but I am blessed. Dorisena