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Study design:Systematic review.
Clinical question:Does single-level unconstrained, semiconstrained, or fully constrained cervical artificial disc replacement (C-ADR) improve health outcomes compared with single-level anterior cervical discectomy and fusion (ACDF) in the long-term?
Methods:A systematic review was undertaken for articles published up to October 2011. Electronic databases and reference lists of key articles were searched to identify US Food and Drug Administration (FDA) studies reporting long-term (≥ 48 months) follow-up results of C-ADR compared with ACDF. Non-FDA trials and FDA trials reporting outcomes at short-term or mid-term follow-up periods were excluded. Two independent reviewers assessed the strength of evidence using the GRADE criteria and disagreements were resolved by consensus.
Results:Two FDA trials reporting outcomes following C-ADR (Bryan disc, Prestige disc) versus ACDF at follow-up periods of 48 months and 60 months were found (follow-up rates are 68.7% [318/463] and 50.1% [271/541], respectively). Patients in the C-ADR group showed a higher rate of overall success, greater improvements in Neck Disability Index, neck and arm pain scores, and SF-36 PhysicalComponent Scores at long-term follow-up compared with those in the ACDF group. The rate of adjacent segment disease was less in the C-ADR group versus the ACDF group at 60 months (2.9% vs 4.9%). Normal segmental motion was maintained in the C-ADR group. Furthermore, rates of revision and supplemental fixation surgical procedures were lower in the arthroplasty group.
Conclusions:C-ADR is a viable treatment option for cervical herniated disc/spondylosis with radiculopathy resulting in improved clinical outcomes, maintenance of normal segmental motion, and low rates of subsequent surgical procedures at 4 to 5 years follow-up. More studies with long-term follow-up are warranted.
Several prospective, randomized, controlled clinical trials regarding cervical artificial disc replacement (C-ADR) have been published. However, the number of C-ADR patients with long-term follow-up for more than 4 years is still sparse. The purpose of this systematic review is to provide a summary of the available literature reporting long-term follow-up of C-ADR and to elucidate whether the favorable outcomes seen in the short-term continue after 4 to 5 years.
Does single-level unconstrained, semiconstrained, or fully constrained C-ADR improve health outcomes compared with single-level ACDF in the long-term?
Study design: Systematic review.
Inclusion criteria: (1) FDA trials comparing C-ADR with anterior cervical discectomy and fusion (ACDF); (2) follow-up ≥ 4 years.
Exclusion criteria: (1) Non-FDA trials comparing C-ADR with ACDF; (2) follow-up < 4 years.
Outcomes: Neck Disability Index (NDI), pain in the neck and arm (Visual Analog Scale [VAS]), Quality of Life (SF-36 Physical Component Score [PCS]), adjacent segment disease (ASD), neurological success, subsequent surgeries, and complications.
Analysis: Descriptive statistics.
Details about methods can be found in the Web Appendix at www.aospine.org/ebsj
Two randomized, multicenter FDA trials comparing outcomes following C-ADR and ACDF with follow-up > 48 months were found (Fig. 1). Inclusion and exclusion criteria and demographic information for each study are listed in Table 1. Overall, a total of 1004 adult patients (47% male) with a mean age of 44 years were included. All patients were diagnosed with single-level degenerative disc disease between C3 and C7 and had failed a minimum of 6 weeks conservative treatment.
Function, pain, and health-related quality of life (Table 2)
Success, ASD, and return to work (Table 3)
At 48 months in the Bryan trial, overall success and NDI success, were achieved in a significantly greater proportion of C-ADR patients compared with ACDF patients (P=.004 and .003, respectively).
At both 48 months in the Bryan trial and 60 months in the Prestige trial, more patients achieved overall neurological success (maintenance or improvement) and were working following C-ADR compared with ACDF, although these differences were not significant.
The rate of ASD at 48 months in the Bryan trial was identical between groups (4.1%); at 60 months in the Prestige trial the rate was 2.9% in the C-ADR group versus 4.9% in the ACDF group, however these differences were not statistically significant.
Range of motion
Subsequent operations (Table 4)
One guideline was found, published by the North American Spine Society (NASS) in 2010, entitled “Diagnosis and treatment of cervical radiculopathy from degenerative disorders.” Among the major recommendations listed were the following statements relevant to the topic of this review:
A 43-year-old woman presented with cervical myelo-radiculopathy that did not respond to medical treatment for 6 weeks. The magnetic resonance images demonstrated a large herniated disc at the level of C5/6, eccentric to the right side (Fig. 2). She then underwent cervical C-ADR at C5/6. Her symptoms improved significantly after surgery and x-rays taken 2 years postoperatively demonstrated very good range of motion at the index level (Fig. 3). Her VAS arm pain score improved from a preoperative score of 8 to a postoperative score of 1 at 2-year follow-up.
The authors have no competing or financial interests to disclose in relation to this work.