New X-rays would be helpful to make sure that the fusion is going well and the instrumentation is well placed (no loosening). The radiculopathy increasing is important as at 3 months, the leg pain should be diminishing. If your physical examination is unchanged (no increased sensory or motor weakness and no increased tension signs), then a short course of oral steroids could be helpful. If exam signs increase, a new MRI would be helpful. I assume you have no fevers or chills.
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.