Multi-level degenerative disc disease: TDR with Mobi-C artificial disc compared to ACDF
Cervical total disc replacement with the Mobi-C cervical artificial disc compared with anterior discectomy and fusion for treatment of 2-level symptomatic degenerative disc disease: a prospective, randomized, controlled multicenter clinical trialJ Neurosurg Spine. 2013 Nov;19(5):532-45
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330 patients suffering from cervical degenerative disc disease (DDD) with radiculopathy or myeloradiculopathy at 2 contiguous levels from C-3 to C-7 were randomized to investigate the benefits of cervical total disc replacement (TDR) using the Mobi-C cervical device (LDR Spine) compared with conventional anterior cervical discectomy and fusion (ACDF). The evidence presented in this study indicated that TDR demonstrated statistical superiority over ACDF based on overall study success rates: both TDR and ACDF groups experienced significant improvements in Neck Disability Index (NDI) score, and VAS neck and arm pain at all time points; however TDR patients demonstrated significantly superior NDI scores at all time points compared to ACDF patients, along with significantly superior VAS neck pain at only 3 and 6 months. TDR group maintained preoperative segmental range of motion at both treated segments immediately postoperatively and throughout the study period. Finally, reoperations were significantly higher in the ACDF group compared to the TDR group.
Was the allocation sequence adequately generated?
Was allocation adequately concealed?
Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?
Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?
Blinding Patients: Was knowledge of the allocated interventions adequately prevented?
Was loss to follow-up (missing outcome data) infrequent?
Are reports of the study free of suggestion of selective outcome reporting?
Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?
Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?
Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?
Yes = 1
Uncertain = 0.5
Not Relevant = 0
No = 0
The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.
Inclusion / Exclusion
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
Anterior cervical discectomy and fusion (ACDF) is considered ‘gold standard’ in treating neurological symptoms and neck pain associated with degeneration of intervertebral discs in the cervical spine. ACDF is however associated with hypermobility, increased stress, and increased intradiscal pressures on the segments adjacent to fused level. Cervical total disc replacement (TDR) is an attractive alternative as it addresses the limitations of ACDF by preserving biomechanics at the adjacent segments, allowing for slower degeneration and reduced pain and neurological symptoms. The current research pertaining to the optimal intervention for degenerative disc disease (DDD) remains controversial, especially as the relevant trials have compared TDR and ACDF only at a single level. Multilevel pathologies tend to be more demanding and therefore this study was needed to compare TDR (Mobil-C cervical artificial disc; LDR Medical) against ACDF for symptomatic cervical DDD at 2 contiguous levels of the cervical spine.
What was the principal research question?
Is there a superior method of fixation for multi-level degenerative disc disease (DDD) between total disc replacement (TDR) with the Mobi-C cervical artificial disc, and anterior cervical discectomy and fusion, as evaluated over 24 months?
What were the important findings?
- The overall clinical success rate in the TDR group was 69.7% compared to 37.4% in the ACDF group (p< 0.05). TDR patients achieved success earlier than the ACDF patients, and maintained it throughout the study.
- Patients in both the TDR and ACDF groups exhibited a marked improvement from baseline in VAS neck (mean change at 24 months: 54 +/- 25 and 53 +/- 29 respectively) and arm pain (mean change at 24 months: 35 +/- 35 and 34 +/- 38 respectively) at all time points. VAS neck pain scores in TDR patients were significantly superior at 3 and 6 months compared to ACDF patients (p< 0.05).
- Mean change in NDI score at 24 months in the TDR group was 37 +/- 20 compared to 30 +/- 19 in the ACDF group. Both groups improved significantly from baseline but the TDR group demonstrated significantly greater scores at every time point compared to the ACDF group. NDI success was significantly higher in the TDR group at all time points (p< 0.05) with 78.2% of TDR patients compared to 61.8% ACDF patients considered a success at 24 months.
- SF-12 evaluations of TDR patients indicated a mean improvement on the physical (PCS) and mental component (MCS) of 13.5 and 9.5 respectively compared to 10.5 and 7.2 in ACDF patients (p= 0.03 at 24 in favor of TDR).
- 7 (3.1%) TDR patients required a subsequent surgical intervention through 24 month's follow-up (4 removals, 2 reoperations, and 1 revision) compared to 12 (11.4%) of ACDF patients (6 removals; 1 revision; 3 supplemental fixations; and 2 reoperations).
- TDR patients exhibited significantly lower incidence of device-related adverse events with rates of 16.7% (39 of 225 patients) compared to 34.3% (36 of 105 patients) in the ACDF group. 23.9% of TDR patients experienced at least 1 serious adverse event compared to 32.4% ACDF patients; however only 3.4% (8) in the TDR and 14.3% (15) in the ACDF cohorts were definitely or possibly related to the device. Overall 3.6% of TDR patients had major complications with an adverse event compared to 6.7% of ACDF patients.
- 5.6% of TDR patients compared to 6.7% of ACDF groups exhibited significant neurological deterioration. This difference was significantly in favor of TDR (p< 0.0001). TDR patients demonstrated significantly superior radiographic success (p< 0.0001): 96.4% of TDR group patients were classified as radiographically successful compared to 79.8% of ACDF group patients. Differences in adjacent-level degeneration rates were significant in favor of the TDR group for both levels at 12 and 24 month follow-ups (p< 0.03).
- 95.8% of TDR patients were satisfied with their treatment compared to 92.0% of ACDF patients, and 95.8% TDR patients would recommend the surgery to a friend compared to 88.5% ACDF patients.
What should I remember most?
Patients in both the cervical total disc replacement (TDR) and anterior cervical discectomy and fusion (ACDF) experienced significant improvements in neck pain, arm pain and disability at all time points. Total disc replacement patients demonstrated significantly superior NDI scores at all time points compared to ACDF patients, along with significantly superior neck pain in the short term (at 3 and 6 months). Total disc replacement patients maintained preoperative segmental range of motion at both treated segments immediately postoperatively and throughout the study period. Reoperations were significantly higher in the ACDF group compared to the total disc replacement group, and the incidence of adjacent-segment degeneration was significantly lower in the TDR group.
How will this affect the care of my patients?
The evidence presented in this study demonstrated the noninferiority and potential superiority of cervical total disc replacement using the Mobi-C cervical artificial disc compared with conventional anterior cervical discectomy and fusion in treatment multi-level degenerative cervical disc disease. While the results presented in this study are promising, controversy still remains about differential efficacy between these treatments over an extended period of time. Long-term evaluation of the Mobi-C cervical disc is required to determine if the benefits observed in this trial are maintained, or lost over a longer time frame.
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