You need to separate your symptoms by percentage into lower back and buttocks/thigh/leg pain. The difference in percentage may indicate the need for different surgeries. If most of your pain is from the buttocks/thigh/leg region, you might be able to undergo a simple microdisectomy. If the symptoms are more heavily weighted to the lower back, a fusion might need to be included in any surgery.
I would think your treating physician would want a new MRI as your symptoms have changed.
Dr. Corenman