mobi-c, disc, replacement, TDR, anterior discectomy and fusion, ACDF, total

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.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.

Study Summary

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."

Outcome Measures

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."