Some surgeons fuse. It's what they know, what they're comfortable with — and for certain problems it's exactly right. But a fusion is forever: it locks a spinal segment solid. It shouldn't be the default answer for every back that hurts. Here's how I think about it.
What fusion does — and what it costs
A fusion joins two vertebrae into one solid bone, eliminating motion at that segment. For instability — a spondylolisthesis that's actively slipping, a deformity, certain fractures — that's precisely what's needed. The segment can't be trusted to move safely, so we stop it from moving. In those cases fusion isn't overkill; it's the correct operation.
The cost is biomechanical: the motion has to go somewhere, so neighboring segments take up extra stress. Over years, that can wear them out faster — adjacent segment disease. It's not guaranteed, and modern techniques have reduced the risk, but it's real. It's the reason fusing a young, otherwise healthy spine deserves a long conversation, not a quick consent form.
When motion preservation wins
Take a herniated cervical disc pinching a nerve in a neck that still moves well. A cervical disc replacement removes the bad disc and implants an artificial one that keeps moving — same nerve decompression as a fusion, but the segment stays mobile and the neighboring levels are spared the extra stress. For the right patient, it's the best of both worlds.
Lumbar disc replacement exists too, though the candidacy is narrower — the lumbar spine carries more load and tolerates less compromise. Significant arthritis, instability, deformity, or poor bone quality can rule motion preservation out at either level. The key phrase is “for the right patient.” The art isn't in the device; it's in the selection.
The lumbar question
Patients often ask why disc replacement is common in the neck but selective in the low back. Load is the honest answer: the lumbar discs bear multiples of body weight with every step, and an artificial disc has to survive decades of that. So in the lumbar spine, fusion remains the workhorse for instability and deformity, while motion preservation is reserved for the narrow group whose anatomy fits the implant's demands — typically younger patients with single-level disc disease, good bone quality, and no facet arthritis. When a patient falls outside that window, the responsible answer is to say so, not to force the technology.
How I decide
Diagnosis first, always: which structure, which nerve, confirmed on exam and imaging. Then a series of questions. Is the segment stable, or does it need to be stabilized? Is there meaningful motion worth preserving? How old is the patient, and how active? A 40-year-old with a single-level herniation and a supple neck is a different decision than a 70-year-old with multi-level arthritis and a slip — same symptom, different spine, different operation.
And sometimes the answer is neither fusion nor replacement. Targeted injections and therapy resolve plenty of cases that arrive in my office pre-booked for the OR. Every operation has to earn its place, including the elegant ones.
What about multi-level disease?
Single-level problems are where motion preservation shines brightest. Multi-level disease is murkier: replacing two or three discs multiplies the selection criteria and the unknowns, and hybrid constructs — a replacement at one level, a fusion at another — are sometimes the honest compromise. Be skeptical of anyone who applies the same operation to every level of every spine. Complexity in the plan should mirror complexity in the problem, and a surgeon who individualizes level by level is doing the hard thinking the case deserves.
If you've been told you need a fusion
Especially a multi-level one — and it doesn't sit right, bring your MRI. I'll tell you whether I'd fuse, preserve motion, or do nothing at all, and show you exactly why. The right operation is the smallest one that solves the actual problem. That's the whole philosophy: match the surgery to the spine, not the spine to the surgery.