Can a tummy tuck with muscle tightening help with spondiolisthesis?

I have spondiolisthesis L3 to L4. Have pain in lower back that goes down hamstring to each knee. I am in physical therapy & have learned to work the muscles that support my back. I will need a L3-L4 fusion. My neck has been fused twice. I can't exercise my abdominal muscles due to the stress on my back and see no other way to tighten them. I am disabled, will my Blue Cross insurance cover this expense? I am of normal weight and in good shape. I've had 3 c-sections, the last in 2006.