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Cervical Disc Replacement: Who It Fits, and How These Implants Fail

By Published

A cervical disc replacement takes out a worn disc in the neck and puts in an implant that still moves. The device labels cover arm pain, numbness, or weakness from a herniation or bone spur between C3 and C7, at one level or two next to each other, usually after six weeks of nonsurgical care. Over ten years extra bone commonly grows around the implant, and one design failed by shedding wear particles.

When a disc in the neck is pressing on a nerve and the pain has not settled with time, therapy, and medication, two operations tend to get discussed. One takes the disc out and lets the two bones grow together. The other takes the disc out and puts in an implant that still moves. This page is about the second one, including the part that rarely makes it into a brochure: how these implants fail, and what has changed because of it.

What the operation actually is

The surgeon works through the front of the neck, takes out the worn disc along with whatever is pressing on the nerve, and puts an implant where the disc used to be. The medical name is cervical disc arthroplasty, and the shorter name most people hear is a cervical disc replacement. The point of the implant is to keep that level bending instead of locking it. Our cervical disc replacement page walks through the operation itself in more detail.

Which necks the labels actually cover

Every one of these implants came to market through a premarket approval, and each carries a label describing who it was tested on. Read together, those labels cover skeletally mature adults with arm pain, numbness, or weakness coming from a disc herniation or a bone spur between C3 and C7, confirmed on imaging. That pattern of symptoms is cervical radiculopathy. Some labels also include pressure on the spinal cord itself, which is cervical myelopathy. One level can be treated, or two levels next to each other. Most labels ask for at least six weeks of nonsurgical care first, or for symptoms that are getting worse on their own.

What rules it out

Plenty of necks are excluded before the conversation starts, and the exclusions are the more useful half of the label. Badly worn facet joints behind the disc rule it out, because those joints have to carry the motion the implant preserves. Thin bone on a DEXA scan rules it out. So does a segment that already shifts too far on bending X-rays, bone spurs that have bridged the level, a neck that has lost its normal curve, active infection, and a known allergy to the implant materials.

When a moving implant is ruled out, fusion is the usual alternative, and it is also the operation these implants were tested against. If you are weighing the two, we lay them side by side in cervical disc replacement versus ACDF, and the ACDF page covers the fusion in its own right.

Bone can grow around the implant

The most common way one of these implants stops behaving like a joint is that bone grows around it. The medical name is heterotopic ossification. In pooled studies following patients at least ten years, that bone was found in about 70 out of 100 people, and in about 37 out of 100 it blocked or bridged the level. Average motion at the treated level went from 8.6 degrees before surgery to 7.4 degrees ten years afterward.

That is worth sitting with, because it reframes what a disc replacement promises. It is not a guarantee of permanent motion. Bending X-rays are how a surgeon checks whether an implant is still moving and still sitting where it was placed, and they are part of the standard follow-up rather than something you only get if something feels wrong.

The failure that changed the conversation

One design failed in a way its five-year trial did not show. The M6-C wound polyethylene fiber around a soft core and held the whole thing inside a plastic sheath. Published reports described that sheath tearing, shedding tiny particles, and setting off bone loss around the implant. In one series of 53 patients, 18 needed the implant taken out and the level rebuilt, on average about five and a half years after surgery. A separate, independent series reported bone loss at a similar order of magnitude, with five implants failing outright. In several of the individual case reports the whole core had moved out of position.

The uncomfortable detail is that this kind of bone loss is often silent. In the larger series the patient-reported scores of the revised group looked much like everyone else’s, which is precisely why the X-ray matters more than how the neck feels.

I want to be exact about the regulatory status, because it gets reported loosely. No FDA recall document for the M6-C was located. What is documented is that the manufacturer discontinued the device in February 2025, issued a field safety notice in August 2025, and that in January 2026 the UK regulator asked that everyone who has one receive a yearly neck X-ray, reviewed whether or not they have symptoms.

What is being done about it

Three things changed. A grading scale for this bone loss was published in 2025, so it gets measured and reported the same way instead of case by case. Monitoring became a formal expectation rather than a matter of local habit. And newer implants use different materials, including one built with plastic endplates and a ceramic core.

There is also a real tension in the literature that no honest summary should smooth over. The five-year FDA trial of the M6-C reported composite clinical success in its favor against fusion. The independent series that found wear-related bone loss followed patients longer, and several of them involved two levels, three levels, or hybrid constructs rather than the single level the FDA had approved. Both sets of numbers are real. What differs is follow-up length, who was in the cohort, and how many levels were operated on.

What this means if you are choosing

None of this makes disc replacement a bad operation. In long-term randomized data, people who had one needed a second operation, including at the neighboring level, less often than people who had a fusion. It remains a reasonable choice for the right neck. What the last few years should change is how much weight goes on the two things around the operation rather than the operation itself: whether your facet joints, bone density, alignment, and stability actually fit the label, and whether someone is looking at your X-rays years later.

If you are trying to decide between these two operations, bring your MRI and your questions. I only operate when it’s truly the right thing for the patient, and when they’ve exhausted every other option first. You can request a consultation or ask for a second opinion, and if you are traveling from elsewhere in the state, our cervical disc replacement in Indiana page covers how that works.

Sources

These are the cards from the carousel version of this article. Each one stands on its own, so you can read them in order or stop at the one you came for.

  1. Carousel cover. The headline asks whether a worn-out disc in your neck can be replaced instead of fused. Beneath it, a full-width band from a side-view neck X-ray shows two metal cervical disc replacement implants stacked at neighbouring levels, with a vertebral body above and below them.
    Card 1 of 9
  2. A three-dimensional educational render of the spine cut open shows a disc replacement implant seated between two vertebrae, with the exiting nerve root highlighted in yellow just above and to the side of the implant and normal discs at the levels above and below. The text explains that the surgeon works through the front of the neck, removes the worn disc and whatever presses on the nerve, and puts the implant where the disc was, and that the medical name is cervical disc arthroplasty.
    Card 2 of 9
  3. Text slide stating that disc replacement is approved for arm pain, numbness, or weakness caused by a disc herniation or a bone spur between C3 and C7, that some labels also include pressure on the spinal cord, and that one level or two adjacent levels can be treated, usually after at least six weeks of nonsurgical care.
    Card 3 of 9
  4. Text slide listing what rules cervical disc replacement out, including badly worn facet joints behind the disc, thin bone on a DEXA scan, a segment that shifts too far on X-ray, bridging bone spurs, active infection, and allergy to the implant materials, with a closing note that fusion is the alternative these implants were tested against.
    Card 4 of 9
  5. Text slide explaining heterotopic ossification, the extra bone that can grow around a cervical disc implant. Pooled studies found it in about 70 out of 100 people ten years after surgery, and in about 37 out of 100 it blocks or bridges the level. Follow-up X-rays are part of the standard check afterward.
    Card 5 of 9
  6. Two side-by-side lateral X-rays from a published figure, labelled A and B, show the same cervical disc replacement with the neck in two different positions, and a black arrow in each panel points to the implant that is failing. The text explains that bending X-rays are how surgeons check that an implant is still moving and still where it was placed, and that they are part of the standard follow-up.
    Card 6 of 9
  7. Text slide describing the M6-C cervical disc, which wound polyethylene fiber around a soft core inside a plastic sheath, and the published reports of the sheath tearing, shedding tiny particles, and setting off bone loss around the implant. In one series of 53 patients, 18 needed the implant removed and the level rebuilt about five and a half years later.
    Card 7 of 9
  8. Text slide noting that the manufacturer discontinued the M6-C in February 2025, that the UK regulator asked in January 2026 for a yearly neck X-ray for everyone who has one, that a grading scale for this bone loss was published in 2025 so it gets measured the same way, and that newer implants use different materials.
    Card 8 of 9
  9. Closing slide with the Greenberg Spine lockup, the line that every patient is unique and your plan should be too, an invitation to bring your MRI and your questions and leave with a written plan, the name Marc Greenberg, MD, the line Orthopedic Spine Surgery, Fort Wayne, and the note that this is educational content and not medical advice.
    Card 9 of 9
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Answers

Frequently asked questions

Who is a candidate for a cervical disc replacement?

The FDA labels cover skeletally mature adults with arm pain, numbness, or weakness coming from a disc herniation or a bone spur between C3 and C7, confirmed on imaging. Some labels also include pressure on the spinal cord. One level or two levels next to each other can be treated. Most labels ask for at least six weeks of nonsurgical care first, or progressive neurologic symptoms.

What rules out a cervical disc replacement?

The same labels exclude badly worn facet joints behind the disc, thin bone on a DEXA scan, a segment that already shifts too far on bending X-rays, bone spurs that have bridged the level, active infection, and a known allergy to the implant materials. A neck that has lost its normal curve is also excluded. Fusion is the operation these implants were tested against, and it is the usual alternative when a moving implant is ruled out.

Does a cervical disc replacement keep moving forever?

Not reliably. Extra bone can grow around the implant, which is called heterotopic ossification. In pooled studies with at least ten years of follow-up it was found in about 70 out of 100 people, and in about 37 out of 100 it blocked or bridged the level. Average motion at the treated level went from 8.6 degrees before surgery to 7.4 degrees ten years after. Follow-up X-rays are part of the standard check afterward.

Was the M6-C cervical disc recalled?

No FDA recall document for the M6-C was located. What is documented is narrower and worth stating precisely: the manufacturer discontinued the device in February 2025, issued a field safety notice in August 2025, and in January 2026 the UK regulator asked that everyone who has one receive a yearly neck X-ray, reviewed whether or not they have symptoms. Those three facts come from the UK regulator's own notice.

Why do the trial results and the later reports disagree?

Because they are measuring different stretches of time. The five-year FDA trial of the M6-C reported composite clinical success in its favor against fusion. The independent series that found wear-related bone loss followed patients longer, and several involved two-level, three-level, or hybrid constructs rather than the single level the FDA approved. Both sets of numbers are real. The difference is follow-up length, who was in the cohort, and how many levels were operated on.

Is a disc replacement a better choice than a fusion?

Neither operation is better in the abstract, and the honest answer depends on your anatomy. In long-term randomized data, people who had a disc replacement needed a second operation, including at the neighboring level, less often than people who had a fusion. But a replacement is only an option if your facet joints, bone density, alignment, and stability allow it. Choosing the right patient and following the implant afterward matter as much as the operation itself.

Talk with a fellowship-trained spine surgeon

Most spine problems improve without surgery. When an operation is warranted, the goal is to match the least-disruptive effective option to the diagnosis and anatomy.

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