systematic review evaluating long-term safety

9Systematic review—Total disc replacement in the cervical spine: a systematic review evaluating long-term safety Study design: Systematic review. Clinical questions: What are the rates and causes of subsequent surgeries? What is the long-term com-plication rates following cervical artificial disc replacement (C-ADR)? How do these rates change over time? Methods: A systematic review was undertaken for articles published up to October 2011. Electronic da-tabases and reference lists of key articles were searched to identify comparative and non-comparative studies reporting long-term ( ≥ 48 months) complications of C-ADR. Two independent reviewers assessed the strength of evidence using the GRADE criteria and disagreements were resolved by consensus. Results: Two RCTs reporting outcomes following C-ADR (Bryan disc, Prestige disc) versus anterior cervi-cal discectomy and fusion (ACDF) at follow-ups of 4 to 5 years were found; five case series reporting outcomes following C-ADR at follow-ups of 4 to 8 years were identified. Secondary surgery rates were similar or slightly lower following C-ADR compared with fusion at 4 to 5 years postoperatively. In one small subset of an RCT, rates of adjacent disc heterotopic ossification were lower in C-ADR patients than in those treated with fusion. Rates of other adverse events were similar between treat-ment groups. Conclusions: There is low evidence on the long-term safety outcomes following C-ADR. Additional comparative studies with follow-up of at least 4 years are needed to fully understand the long-term safety outcomes of C-ADR compared with fusion