A CT scan is the gold standard for fusion determination. X-rays are easier to obtain so I generally start there but if you can get a CT scan, that would be helpful. Surgery can be permanent at that level if you have a fusion and it heals solidly. An artificial disc replacement can be helpful in the correct circumstances but will eventually one day wear out (after all, it is a mechanical device) and need to be revised.
For lower back pain, if massage helps, then use that therapy as long as it works and is not too frequent.