Discograms would not be helpful to you as you have no discs below L2-3 to diagnose. Your pain could be from lack of fusion (pseudoarthrosis) and you would need a fine-cut CT scan to determine this. You could also have chronic nerve injury causing pain.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.