Is spine fusing a better option than disc replacement?

Depends. It depends on the age of the patient, how many levels are involved, if instability is present, and how much degeneration is present in the spine. It would be best to have a spine surgeon fully evaluate you with imaging studies and a physical exam. There are people that would not qualify for disc replacements and a fusion would be a better option.
Varies. The results for disc replacement and a spine fusion are equivalent when the appropriate indications and guidelines are respected and followed and when done by qualified orthopedic spne surgeons or neurosurgeons.

Related Questions

How effective are disc replacement options in lumbar spine? Cervical spine?

See below. They are safe and effective and have similar results as the clasSic ACDF their advantages over the fusion are theoretical in my opinion the Acdf has a 95% chance at relieving arm pain neither are neck pain procedures, both do a good job relieving arm pain from pinched neck nerves early adopters of new technology can be surprised by outcomes since they are not as well studied without long term.