Adults suffering from pain, loss of function, and poor quality of life do have the three basic treatment options you mentioned: 1) conservative care and rehabilitation, 2) spinal fusion, or the newer option of 3) disc replacement. Your question of which is best is a good one and one that even surgeons are grappling with.
In order to find out how to advise their patients, surgeons from The Netherlands conducted an extensive survey of the published studies comparing these three approaches. Current clinical practice seems to be moving away from spinal fusion and more toward lumbar disc replacement for symptomatic degenerative disc disease. The implants were first invented and designed to help with the problem of adjacent spinal disease that often occurs at the level above or below a fused segment.
But do they really protect the spine as intended? That’s one question that needs to be answered. They are expensive and long-term results are limited. After an extensive search on-line, the surgeons from The Netherlands found seven studies that compared results of disc replacement, fusion, or rehabilitation. Combining all the patients in all seven studies, there was a total of 1301 people included. Only one of those studies really looked at rehabilitation.
Analysis of findings showed that patients improved no matter what type of treatment was applied. Patient satisfaction was greater in the group who had a total disc replacement. As intended, these implants did allow patients more natural motion.
None of the studies looked at subsequent adjacent segment disease, which is the main reason the implants were developed in the first place. The follow-up was two years or less, so long-term results weren’t really available.
You are essentially asking about something surgeons refer to as salvage procedures. If conservative care fails to help you, then surgery may be the next step. But there are many types of nonoperative treatment. Finding the right one (or combination of two or more) can take some time.
Salvage options after spinal fusion are fewer than after disc replacement. If the disc implant doesn’t work for any reason, you can always have it removed and then have the spine fused. In some cases, a failed disc implant can be removed and replaced with a new implant (different design).
Understanding salvage options is important when deciding in favor of one treatment over another. You will want to talk with your surgeon about all your options — both before and after surgery of any kind. There may be some specific reasons related to your case that would make one type of treatment a better option than another.