Spine

Cervical Disc Arthroplasty Over Fusion — A Long-term RCT Finds No Benefit

Most patients going with ACDF aren't giving anything up — but some may need an alternative

What’s the Claim

A 5-year follow-up on a well-designed randomized controlled trial found no advantages to cervical disc arthroplasty over anterior cervical discectomy and fusion (ACDF) for patients with single-level cervical radiculopathy from disc herniation. The proportion of patients who underwent reoperation for adjacent-segment symptoms was about 2% per year both in the arthroplasty and ACDF groups, and outcomes scores in those groups were almost identical. There were no reoperations for adjacent-segment degeneration in the third study group (anterior cervical discectomy alone without a cage or plates); that group’s outcomes scores were statistically worse (though probably not enough for patients to notice), and those patients had more reoperations at the index level. Finally, the authors noted a decrease in the overall reoperation rate over time, from 3.6% per year in the first two years (a function of typical early complications of major surgery) to under 2% per year thereafter.

How’s It Stack Up?

Earlier studies related to the FDA’s approval process of these devices (which now have intermediate- to long-term follow-up) favored cervical disc arthroplasty, while a number of more-recent RCTs, which now also are out 5 to 10 years, did not. The more-recent trials were large enough and follow-up long enough to have discerned important differences in adjacent-segment degeneration between fusion and arthroplasty, if such a difference were present. In general, this goes for differences in outcomes scores, which didn’t differ between fusion and arthroplasty in most of the “second round” RCTs. What should we do when some (very selective) earler IDE studies found an advantage to cervical disc arthroplasty, while a number of other more-recent ones (that may have had more “real-world” inclusion criteria) did not?

What’s Our Take?

We need to choose patients wisely. If surgeons seek to replicate the (favorable) results of those IDE studies, they need to replicate the very stringent inclusion criteria those studies used. CORRelations’ Spine adviser shares that “every patient who is a candidate for a cervical disc arthroplasty can have a fusion, but not every candidate for fusion is a candidate for ACDF.” In general, the key benefit theorized to favor cervical disc arthroplasty — avoiding adjacent-segment degeneration from fusion — has not consistently been realized. CORRelations’ Spine adviser also suggests that adjacent-segment degeneration in the years after surgery may have as much to do with the amount of adjacent-segment degeneration present before the procedure; he even says that looking at the presence of arthrosis in the lumbar spine for clues to what may happen over time to patients having these cervical procedures may be worthwhile. Finally, he offers that “relative contraindications for arthroplasty may include low bone density, instability, facet joint degeneration, and disc space collapse” and “CDA is not good for extensive spondylytic disease. If I think I am going to have to remove a substantial amount of bone either central or in the foramen to accomplish adequate decompression, I will fuse.” The post-IDE generation of randomized trials supports his view; these studies now are out beyond 5 years, and they don't show a strong benefit of cervical disc arthroplasty over fusion for patients with single-level disease. In light of that, surgeons can be comfortable telling their patients they’re not giving anything up by going with the tried-and-true for this diagnosis — ACDF — other than for very carefully selected patients.