There is a section on the website that discusses “failed spine surgery syndrome” under “conditions”. Please peruse this and it may answer some of your questions.
There is a standard work-up to be done if spine surgery has failed. With a prior fusion, this would include a new MRI, new x-rays, a CT scan and a new physical examination. Comparison to your prior work-up for surgery is performed and potential diagnoses are elucidated.
Dr. Corenman