Two-level cervical disc arthroplasty is an effective alternative to ACDF at five years

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A study has indicated statistical superiority of cervical disc arthroplasty over two-level anterior cervical discectomy and fusion (ACDF) at five years in overall success, Neck Disability Index (NDI) and Short-Form 36 (SF-36) physical component scores. The data were presented by Matthew F Gornet, The Orthopaedic Center of St Louis, St Louis, USA, at EUROSPINE 2015.

Cervical disc arthroplasty offers a motion-preserving alternative to ACDF in radiculopathy and myelopathy patients who are unresponsive to conservative treatment. However, few studies have looked at its efficacy over two contiguous levels.

Gornet and colleagues used a low-profile, titanium ceramic composite ball-in-trough investigational device, which had previously shown 24-month superior success at two levels compared with two-level ACDF. This new data followed patients out to five years post-surgery.

The prospective, randomised, controlled multicentre Food and Drug Administration Investigational Device Exemption study took place at 30 US centres and involved 397 patients with cervical degenerative disease at two contiguous levels (C3-C7). The patients were randomised to be treated with either ACDF or arthroplasty, and were then followed at regular intervals for 24 months, and again at 36 and 60 months post-surgery.

A classification of “overall success” required patients to exhibit all of the following: NDI improvement ≥15 points (NDI success), maintenance or improvement of neurological status, no serious implant or implant/surgery-related adverse events and no additional surgical procedures at the index levels. Once non-inferiority was concluded using Bayesian statistical methods, the team were able to test for superiority.

Gornet reported superiority of cervical disc arthroplasty over ACDF in overall success, NDI success and SF-36 physical component success. This was the case at every time point throughout the study’s follow-up. At 60 months, the arthroplasty overall success rate was 79.5% compared with 65.9% for the ACDF group (posterior probability of superiority=99.6%), while NDI success was 89.2% in the arthroplasty group compared with 77.8% for ACDF (posterior probability of superiority=99.6%).

Five-year serious implant or implant/surgery-related adverse events rates were similar between the two groups, reported as 23.2% in the arthroplasty group and 24.7 in the ACDF group. However, subsequent surgery rates at the index level were significantly higher in the ACDF group (11.5% [8.7% when excluding external bone growth stimulators]) than in the artificial disc group (4.2%). Grade III or IV heterotopic ossification was also higher in the ACDF group (8.4%) than in the disc arthroplasty group (3.6%).

“This study presents long-term Level 1 clinical evidence in support of cervical disc arthroplasty at two contiguous levels as a motion-sparing alternative to ACDF in appropriately selected patients,” Gornet told delegates.

Interestingly, Gornet mentioned that “at around five years, we do not see a significant difference between a single-level arthroplasty and a single-level fusion, but if you look at that at two levels, those results really stratify, and what you are seeing is much more evidence of statistical superiority.”

Referring to the cost benefit of the different procedures, Gornet said that for two-level cervical disc arthroplasty, “that is still under analysis. In the single-level it has been found that arthroplasty has a cost benefit over ACDF—the surgery itself was similar, but the benefit was driven by two factors. The first was an earlier return to work for patients in the arthroplasty group and the second was fewer reoperations.”

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