When a damaged disc has to be removed, the gap it leaves must be dealt with. There are two philosophies, and they lead to very different spines.
Fusion: make the segment solid
The disc is removed, a spacer (cage) is inserted, and the two vertebrae are joined with screws so they heal into one solid block. That segment no longer moves.
Fusion is reliable, long-established, and remains the right answer when the spine is unstable — a slipping vertebra, significant deformity, or a segment that is mechanically unsound. You cannot preserve motion in a segment that needs to stop moving.
Disc replacement: keep the segment moving
The damaged disc is replaced with an artificial one that continues to bend and rotate, preserving movement at that level.
The reason this argument matters: adjacent-segment disease
When you fuse a segment, it stops moving — but you still need to bend. That movement has to come from somewhere, so the levels immediately above and below take up the slack. Over years, that additional load may accelerate their wear. This is known as adjacent-segment degeneration, and it is a recognised long-term concern with fusion, particularly in younger patients who have decades of loading ahead of them.
By maintaining movement at the operated level, disc replacement aims to reduce that extra strain on the neighbours. This is the central argument for motion preservation, and it is why age matters so much in the decision.
Who qualifies for disc replacement
It is not for everyone. Broadly, a good candidate has:
- Disc disease at one or two levels, with pain arising from the disc or from nerve compression
- A stable spine — no significant slippage of one vertebra on another
- Reasonably preserved facet joints (the small joints at the back of the spine)
- Adequate bone quality — significant osteoporosis is a problem
- No major deformity, active infection, or tumour
Instability, severe facet arthritis or poor bone quality all push the decision back towards fusion. In those situations fusion is not the inferior option — it is the correct one.
How to think about it
The question is not "which is better?" but "which does my spine need?" A younger patient with a single-level disc problem and a stable spine is a very different case from someone with a slipping vertebra and arthritic facet joints. The honest answer is that both operations are right — for different people.
Concerned about back or neck pain? Dr. M.D.S. Sasidharan offers endoscopic, minimally invasive and non-fusion spine care at Iswarya Hospital, OMR, Chennai. Book a consultation to find out whether you can avoid surgery altogether.
Frequently Asked Questions
Is disc replacement better than fusion?
Neither is universally better. Disc replacement preserves movement and may reduce strain on the adjacent levels, which is attractive in younger patients. But it requires a stable spine with healthy facet joints and good bone quality. Where there is instability, deformity or significant facet arthritis, fusion is the correct choice.
What is adjacent-segment disease?
When a spinal segment is fused it no longer moves, so the levels above and below take on additional movement and load. Over years this can accelerate their degeneration. Motion-preserving surgery such as disc replacement aims to reduce this risk.
How long does an artificial disc last?
Modern artificial discs are designed for long-term durability and are made from materials used successfully in hip and knee replacements. Long-term studies show good survival, though as with any implant, revision surgery is occasionally required.