In October 2015, Austin-based LDR Spine released five-year follow-up data for its flagship cervical disc arthroplasty implant, Mobi-C. LDR released 5-year data for BOTH single and double levels. (Both studies were prospective, randomized 2:1, multi-center, two arm, unmasked, concurrently controlled, non-inferiority clinical studies.)
Also released in 2015 were a dozen additional disc arthroplasty studies including a 5-year follow-up for the NuVasive, Inc. PCM cervical disc, 7-year follow-up for the Depuy Synthes ProDisc-C and, just for the record, an 11-year follow up data for the Charité III lumbar disc replacement.
And to make the point that the most recent data is standing on the shoulders of several dozen other investigators, 2016 marks the 10-year anniversary of Fred Geisler’s review of the original design and clinical testing of the first true disc arthroplasty implant—the Charité. In 2006 Geisler reviewed 10 years of Charité clinical data—which had been implanted in about 15, 000 patients by then.
So as of 2016, clinicians, regulators and payers have 20 years of disc arthroplasty data including multiple FDA approved, prospective, randomized, blinded clinical studies and data on tens of thousands of patients from Europe.
10 Years Ago
Charité was approved by the FDA in October 2004. Worldwide, at the time of approval, the Charité had been implanted in more than 10, 000 patients.
Fred Geisler, M.D., Ph.D, in his 2006 commentary and review wrote:
“The early experience with the CHARITÉ prosthesis is mixed largely due to limited sizing, rudimentary instrumentation and underdeveloped patient indications. The challenges of the early experience were a necessary step in refining the indications and techniques for lumbar disc replacement in preparation for the FDA Investigational Device Exemption (IDE) study.
In 2006, there was already data from European disc arthroplasty patients with 10-year follow up. Lemaire et al. described clinical and radiographic results in 10 patients with a minimum 10-year follow-up period after disc replacement. They reported excellent or good clinical outcomes in 90% of patients, with a mean range of motion in flexion/extension of 10.3 degrees.
The return to work rate was 92%.
There was a 2% incidence of adjacent-level disease requiring reoperation, and a 5% incidence of posterior revision with no anterior revision procedures.”
What Have We Learned so Far?
Twenty years of research is illuminating. Reading the early studies and then walking with the investigators through the years shows how science builds incrementally. You can’t exaggerate the importance of iterative studies.
Each one brings an element of ‘truth.’
In the early days, the excitement around motion preservation was exhilarating and you can read it in those early commentaries.
Then the analysis of the revisions emerged.
Then the critics began looking at methodologies of the early studies.
Then the core assumptions behind motion preservation were tested—is adjacent level disease real, for example.
At each level, more ‘truth’ emerged and built on everything that came before.
Today, disc arthroplasty—revised and improved—stands on solid ground. Companies have improved the instrumentation dramatically. Patient selection is much more accurate and, most importantly, the implants themselves and the surgical procedures are vastly better.
Those important advancements have found voice in the North American Spine Society (NASS) clinical guidance statements and the International Society for the Advancement of Spine Surgery (ISASS) policy statements which were issued in 2015. Both societies articulated support for the use of disc arthroplasty to treat patients with degenerative disc disease.
ISASS wrote:
“Based on a thorough review of the best available evidence-based scientific literature the International Society for the Advancement of Spine Surgery concludes that lumbar TDR [total disc replacement] is not new, experimental, or investigational. It is a well-tested technology which should predictably lead to better outcomes and less complications than fusion surgery, as well as a protective effect on adjacent levels.
There is sufficient evidence-based scientific evidence to support the safety and efficacy of single level lumbar TDR for patients meeting well established selection criteria. ISASS would support patient authorization guidelines that mirror the selection criteria from the IDE studies, as long as the device is implanted by a trained experienced spine surgeon.
There are now several long-term prospective and retrospective studies available on lumbar TDR which provide objective evidence regarding their safety and effectiveness. Data from prospective randomized clinical trials have reported consistently low rates of re-operations, and extremely low levels of particulate wear debris complications. A list of relevant research is available below.
Based on sound analysis of the scientific literature, the International Society for the Advancement of Spine Surgery recommends universal coverage for single level lumbar TDR in patients meeting the established selection criteria.”
Then NASS wrote:
“Cervical artificial disc replacement (CADR, also known as cervical total disc replacement and cervical arthroplasty) may be indicated for the following diagnoses with qualifying criteria, when appropriate:
- Radiculopathy related to nerve root compression from one or two-level degenerative disease (either herniated disc or spondylotic osteophyte) from C3-4 to C6-7 with or without neck pain that has been refractory to medical or non-operative management.
- Myelopathy or myeloradiculopathy related to central spinal stenosis from one or two level degenerative disease (either herniated disc or spondylotic osteophyte) from C3-4 to C6-7 with or without neck pain.”
The Mobi-C Two-Level Study 5-Year Results
This is a prospective, randomized, FDA supervised IDE study which is designed for a 7-year follow-up. At the 2-year and 5-year marks, Mobi-C demonstrated fewer subsequent surgeries, lower rates of adverse events, lower rates of adjacent level degeneration, and higher NDI (neck disability index) success rates compared to anterior cervical discectomy fusion (ACDF). In fact, at the five year mark, the NDI success score actually improved for those patients who received a two-level Mobi-C At 60 months of follow-up, Mobi-C is statistically superior in terms of overall study success for two-level use.
Here are the results:
Two-level patients at two years
- NDI Improvement:
- Randomized Mobi-C (n=225): 2% (169/216)
- Randomized ACDF (n=105): 8% (55/89)
- No Failure due to Subsequent Surgery:
- Randomized Mobi-C (n=225): 9% (218/225)
- Randomized ACDF (n=105): 6% (93/105)
- No Major Complications
- Randomized Mobi-C (n=225): 6% (197/225)
- Randomized ACDF (n=105): 4% (76/105)
- Overall Success
- Randomized Mobi-C (n=225): 7% (154/221)
- Randomized ACDF (n=105): 4% (37/99)
Two-level patients at five years
- NDI Improvement:
- Randomized Mobi-C (n=225): 0% (159/194)
- Randomized ACDF (n=105): 6% (43/76)
- No Failure due to Subsequent Surgery:
- Randomized Mobi-C (n=225): 0% (216/225)
- Randomized ACDF (n=105): 8% (88/105)
- No Major Complications
- Randomized Mobi-C (n=225): 1% (187/225)
- Randomized ACDF (n=105): 1% (82/105)
- Overall Success
- Randomized Mobi-C (n=225): 8% (120/191)
- Randomized ACDF (n=105): 1% (30/88)
The PCM Cervical Disc 5-Year Results
This is a prospective, randomized, FDA supervised IDE study which is designed for a 7-year follow-up.
Here are the results:
At the 5-year follow-up mark, all patient reported outcomes—neck and arm pain visual analogue scale score, neck disability index and general health (36-item short form health survey physical and mental component scores: physical component summary, mental component summary)—were significantly improved from baselines in both groups, and mean scores were significantly better in the PCM group for neck disability index, neck pain, general health and patient satisfaction.
- 2 to 7-year device related adverse events
- Randomized PCM: 5% (1/214)
- Randomized ACDF: 1% (2/190)
- Secondary Surgical Procedures
- Randomized PCM: 3% (7/211)
- Randomized ACDF: 6% (14/290)
- Adjacent-level degeneration as measured radiographically
- Randomized PCM: 1%
- Randomized ACDF: 9%
The author’s conclusion: The long term results show good clinical outcomes after ACDF and PCM arthroplasty. PCM patients showed greater improvement in neck disability index and neck pain scores with a lower rate of radiographically adjacent-level degeneration and a trend toward fewer secondary procedures. These data support PCM arthroplasty to be a viable and sustainable alternative to ACDF.
The ProDisc-C 7-Year Results
At seven years, the overall follow-up rate was 92% (152 of 165). There were no significant differences in demographic factors, follow-up rate, or patient-reported outcomes between groups.
Both procedures were effective in reducing neck and arm pain and improving and maintaining function and health-related quality of life.
Neurologic status was improved or maintained in 88% and 89% of the patients in the ProDisc-C and ACDF groups, respectively.
After seven years of follow-up, 30 secondary surgical procedures had been performed in 19 (18%) of 106 patients in the ACDF group compared with seven secondary surgical procedures in 7 (7%) of 103 patients in the ProDisc-C group (p = 0.0099).
There were no significant differences in the rates of any device-related adverse events between the groups.
Said the study authors: “Total disc arthroplasty with ProDisc-C is a safe and effective surgical treatment of single-level symptomatic cervical degenerative disc disease. Clinical outcomes after total disc arthroplasty with ProDisc-C were similar to those after ACDF. Patients treated with ProDisc-C had a lower probability of subsequent surgery, suggesting that total disc arthroplasty provides durable results and has the potential to slow the rate of adjacent-level disease.”
Final Thoughts
The Mobi-C 5-year data is impressive. As is the PCM 5-year and the Pro-Disc 7-year and, yes, the Charité 11-year data (see table at the end of this article).
Investigators who’ve been working with disc arthroplasty patients for all these years have told us that disc arthroplasty patients go home sooner, go back to work in greater numbers and report a better quality of life than their spine fusion counterparts.
Two decades and hundreds of clinical studies work including several level 1 clinical trials, steady improvement in instruments, implants and patient selection and published support from two major spine surgeon societies begs two questions:
- Why do major health insurance carriers in the U.S. continue to describe disc arthroplasty as an experimental treatment and therefore refuse to provide reimbursement for disc arthroplasty even in patients who meet strict selection criteria?
- Why are payers denying an effective and well documented treatment for millions of Americans with chronic and debilitating lumbar or cervical degenerative disc disease?
