Safety and Effectiveness of Two-level Total Disc Replacement (TDR) versus Two-level Anterior Cervical Discectomy and Fusion (ACDF)
Meeting Highlight from NASS 2014
During the North American Spine Society's 29th Annual Meeting, Dr. Reginald J. Davis presented results of a study of the safety and effectiveness of 2-level total disc replacement (TDR) compared to an anterior cervical discectomy and fusion (ACDF) control group. The title of the study is Two-level Treatment with Total Disc Replacement versus ACDF: Results from a Prospective Randomized Clinical trial with Five Years Follow-up.
Although several TDR devices are on the market, few have been clinically evaluated for 2-level use. In this prospective, randomized, controlled, multicenter (24 sites) trial, Mobi-C® (LDR Spine, Austin, Texas) was the investigational device. The control was ACDF with allograft and anterior plate and screws.
The study included 330 patients randomized 2:1. Inclusion criteria included diagnosis of symptomatic cervical degenerative disc disease at two levels (C3-C7), unresponsive to non-operative treatment(s), and no previous history of cervical fusion surgery.
- 2-level TDR: 225 patients
- 2-level ACDF: 105 patients
Dr. Davis explained, "Our hypothesis was these TDR patients will continue to demonstrate superiority compared to ACDF in 2 years, to what is now 5 years of follow-up." Furthermore, he said, "Patient follow-up was robust. At the beginning, 95 with 89% and even after 5 years, 91% of the TDR and 87% of the ACDF patients were still available for evaluation."
Extensive outcome measures included:
- Neck Disability Index (NDI)
- Visual Analogue Scale (VAS)
- Range of motion
- Patient satisfaction
- SF-12 Physical and Mental Health Composite Scores (PCS, MCS)
- Major complications
- Subsequent surgery rate
- Overall success rate
Dr. Davis stated, "The mean NDI scores … and substantial improvement in both groups. And I can't emphasize that enough, the ACDF is an excellent operation. However, at every time frame, there was a statistically significant better outcome with TDR versus ACDF, and this is as true at 5 months as it was at 2 years."
- Return to work: The patients who received TDR returned to work more quickly—46 days versus 67 days.
- Arm pain: The patients who received TDR had better recovery of arm function with less pain.
- Range of motion: ACDF eliminates motion at the superior and inferior levels. TDR preserves range of motion, which was still apparent at 5 years.
- Patient satisfaction: Very high for both the TDR and ACDF groups. However, at 5 years, the patient satisfaction rate was statistically better in the TDR group.
- SF-12 PCS and MCS: In the mental component, the results for both groups were similar. However, in the physical component, patient satisfaction was statistically greater among the patients who received TDR.
- Major complications/adverse events: Near the 5 year follow-up point, the TDR group experienced fewer major complications and adverse events.
- Subsequent surgery: "When we look at subsequent surgeries at the index levels there were -statistically significant- fewer subsequent surgeries for the TDR versus ACDF at 3.8% versus 16.2%, respectively," stated Dr. Davis.
Concluding Comments by Reginald J. Davis
"This is the first long-term clinical evidence from an FDA IDE trial on 2-level patients. The follow-up rates were the highest of any study at this level at this time: TDR followup at 90.7% and ACDF followup at 86.7%."
- Mobi-C® patients maintained segmental range of motion through 5 years compared to the ACDF patients.
- Two-level Mobi-C® patients experienced statistically significant benefits over ACDF patients at 60 months (eg, NDI, VAS scores).
- "Overall study success rates demonstrated that Mobi-C® at two contiguous levels should be a superior alternative to ACDF through 5 years."