Charité is gone. Several more including CerviCore, Discover and NeoDisc never made it to market.
But the Bryan, Prestige ST, ProDisc, Secure-C, PCM and Mobi-C did.
Kineflex C is close.
It has been nearly 10 years since the first total spine disc arthroplasty (TDA) was implanted in a patient in the U.S. Some discs have left the market. More failed to get through the FDA or Centers for Medicare and Medicaid Services (CMS) or corporate budget gauntlets.
An impressive number—whether still commercially available or not—live on in the patients who received them.
Like ghosts from Christmas past, these implants walk into physician’s offices at regular intervals and present themselves for review.
Who’s still standing and what’s on the Horizon?
With Charité exiting the market two years ago, ProDisc (JNJ/Synthes) is the only lumbar TDA available in the U.S. Six cervical TDA’s, however, have FDA approval and are for sale.
In fact, the pace of approvals seems to have accelerated in the last couple of years. Secure-C, PCM and Mobi-C were approved by the FDA in 2012. Then last year, the FDA granted LDR Spine a 2-level indication for its Mobi-C.
National coverage for these TDA’s has been spotty but Aetna, UnitedHealthcare and Cigna have now announced national TDA coverage.
With luck, CMS may approve a new CPT code for 2-level disc arthroplasty in 2015.
Two discs—Prestige LP and Kineflex-C—have completed their investigational device exemptions (IDE) studies and are awaiting FDA action. Both are metal on metal cervical disc replacements.
Finally, as we noted above, two TDAs (CerviCore and Discover) were moth balled despite completing IDE studies (like ghosts of Christmas past…).
And there are at least a couple more TDA’s sticking their toes into U.S. spine markets (Activ-C and M6-C).
The Data
At Castellvi’s Duck Key meeting in early April, Jack Zigler, M.D. (Texas Back Institute (TBI), Plano, Texas) and Dom Couric, M.D. (Chief, Department of Neurosurgery, Carolinas Medical Center, Charlotte, North Carolina) updated data on the multi-year performance of several of these discs—even the ones which are no longer commercially available.
As a group, they are holding up well. Patients with TDA’s are less likely to need re-operations and report greater neurological success than their fusion counterparts.
As for adjacent level disease…also better outcomes than fusion patients, but there is new and better thinking about what adjacent level disease is and what its incidence rates are.
There is now seven-year data on the ProDisc-C and the Prestige-ST. There is five-year data available for the ProDisc-C. And there is two-year data for the Bryan, Prestige-ST, ProDisc-C, Secure C, PCM and Mobi-C.
The results, importantly, are consistent across the studies and each version of a cervical TDA.
Re-operation rates (data from Jack Zigler, M.D.) were 8.3% for the disc replacement (DR) patients versus 21.2% for the anterior cervical fusion (ACF) patients.
Here’s the table from Dr. Zigler’s presentation at Duck Key
Cervical Disc vs. Fusion
Texas Back Institute has been one of the most prolific clinical study sites for cervical total disc replacements. All told, TBI physicians enrolled 136 patients in 1 of 6 prospective, randomized FDA IDE total cervical disc replacement trials. Of that group, 84 patients received a cervical disc replacement and 52 received an anterior cervical fusion.
The longest follow up at TBI, which may well be the longest TDA follow up of any clinic or hospital in the U.S., is eight years.
Picking one of the studies (ProDisc-C) at seven years, here is what the data looks like (Delamarter et al.)
Interestingly, the longer term TDA data has NOT shown a “tail-up” of Visual Analog Scale (VAS) or Oswestry Disability Index (ODI) scores. A “tail-up” refers to patient satisfaction peaking and then deteriorating as the years go by. For example, the neck disability index scores for ACDF (fusion) patients declined slightly from the 24 months to 84 months period. At 24 months fusion patients reported 60% improvement. At 84 months fusion patients worsened slightly and reported 56% improvement. By contract the C-TDA patients reported 60% improvement at 24 months and then rose slightly to 64% at 84 months. No “tail-up” in other words for the TDA patients.
The Meta-Analysis
The amount of FDA sanctioned clinical studies of cervical artificial discs is impressive. As Dom Couric, M.D. explained in his Duck Key talk, six discs completed their IDE studies and are (or were) available for implantation in the U.S.—the Bryan, the Prestige ST and the ProDisc-C and recently, the Secure-C, the PCM and the Mobi-C 1 and 2 level. One disc is close to completing its study and that is the Kineflex C.
In 2012 the Journal of Neurosurgery: Spine published a meta-analysis of three U.S. FDA IDE cervical arthroplasty trials. The authors (Updadhyaya, Jau-Ching, Trost, Haid, Traynelis, Tay, Coric and Mummaneni) reviewed two-year follow up data from the Prestige ST, Bryan and ProDisc-C trials covering 621 TDR patients vs. 592 ACF patients. Fully 94% of the TDR patients and 87% of the ACF patients completed the two-year follow up.
Ninety-five percent of the ACF patients had a successful fusion.
Here is what the researchers found:
• There was no significant difference between the two groups with respect to ODI, SF-36 or pain scores.
• BUT, patients who’d received the TDR had significantly lower re-operation rates, greater neurological success and a lower adjacent level re-operation rate
These conclusions were consistent across all the studies and mirrored the TBI experience with their six different IDE studies.
Cervical Disc Replacement 12% Cheaper Than Fusion, on Average
Here are the TBI numbers. Fusion advocates; read ’em and weep.
On the day of surgery, CDA (cervical disc arthroplasty) is about 10% cheaper—$20, 722 for a cervical disc replacement vs. $22, 379 for a cervical fusion. But then the savings mount up during patient follow up.
The savings are even more impressive when looking at cost/month. By the third year, CDA patients cost the system about $761.75 per month while the fusion patients were almost 30% more expensive at $982.35 per month.
Adjacent Level Disease – Misunderstood and Overstated
One of the reasons for artificial disc replacements over fusion is the possibility of degenerative disc disease developing in an adjacent disc level. As the data from multiple IDE studies has shown, TDA does appear to reduce the incidence of adjacent level degeneration.
But…
Have physicians been mis-understanding and overstating the issue of adjacent level disease? Dr. Coric tackled this very interesting question at the Duck Key meeting. The answer is actually “Yes!”
Adjacent level disease is defined as radiographic evidence of disc deterioration above or below the operative level. Clinically this would manifest itself as symptomatic changes which can credibly be attributed to the adjacent levels.
How prevalent is this problem? Probably the most common answer to that question is that 2.9% of the fusion patients will return annually for a re-operation due to some symptomatic disc degeneration at the level adjacent to the operative level.
And probably the most commonly cited paper to support that 2.9% number is Hilibrand’s landmark study of adjacent level disease.
But Hilibrand never showed a 2.9% rate. In fact, the number is closer to 0.72%. Dr. Coric did the math. Number of fusion procedures over 10 years in Hilibrand’s study = 409 (374 patients). Number of patients who returned for re-operation at the adjacent level = 27. Twenty-seven patients out of 374 patients = 7.2% over 10 years.
So, divide 7.2% by ten to get the annual number and it is…0.72%. Which is about 4 times less than 2.9%.
What’s the Real Bottom Line?
What’s the point of replacing fusion with arthroplasty if we’ve been overstating the re-op rate due to adjacent level disease?
The Updadhyaya et al. meta-analysis (Journal of Neurosurgery:Spine, 2012) looked at 1, 213 patients with a minimum of two-year follow-up (cervical total disc replacement: n=621 and for anterior cervical disc fusion: n=592) found that TDR patients had a statistically lower rate of secondary surgery (cTDR 3.1% vs. ACDF 8.2%). The analysis also found a statistically superior rate of success at two-year follow-up.
The McAfee et al. meta-analysis of four FDA approved cervical TDR studies (Spine Journal) looked at 1, 707 total patients (of which 1, 205 had two-year follow-up) and found that TDR patients had a statistically superior rate of clinical success (cTDR 77% vs. ACDF 69%). The study also found that ACDF patients were statistically more likely to have a second surgical procedure.
In the Kineflex C study (Coric et al., Journal Neurosurgery: Spine, 2011) the ACDF patients had a statistically significant rate of adjacent level disease. Same results from the ProDisc-C study (Spivak et al., CSRS, 2012). Same results from the Mobi-C study (Hisey et al., NASS, 2011).
Bottom line: Whether you want to reduce the risk of adjacent level disease or not, using cervical total disc replacement in the right patients has been shown to reduce the rate of reoperations, deliver higher rates of clinical success and reduce costs as compared to anterior cervical fusion procedures.
Thanks to both Drs. Coric and Zigler for allowing us to use their strong presentations to build this article.
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