The two potential problems that come to mind are missed upper lumbar foraminal stenosis and alignment issues. Do you have normal sensation in your groin and thighs or diminished? Do you have standing full spine x-rays (scoliograms)? I assume your MRIs covered the thoraco-lumbar spine.
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.