The Incidence of Adjacent Segment Pathology After Cervical Disc Arthroplasty Compared with Anterior Cervical Discectomy and Fusion: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Objective: The aim of this study was to assess rates of adjacent segment degeneration (ASDeg), adjacent segment disease (ASDis), and reoperation rates as a result of adjacent segment pathology in patients who have undergone anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA). Methods: A comprehensive search of randomized controlled trials was performed in PubMed from 2012 to 2019. Relevant studies included were assessed for quality using the Cochrane Beck Review Group guidelines. Rates of ASDeg, ASDis, and reoperation because of adjacent segment pathology were extracted and included in the final analysis. A random-effects and fixed-effects model was run among studies that showed high and low heterogeneity, respectively. Results: A total of 19 studies were included in the final analysis, comprising 4655 patients. Overall, ACDFs reported significantly higher rates of ASDeg (19.7% vs. 14.4%; P < 0.001), ASDis (6.1% vs. 3.8%; P < 0.001), and reoperation rates (6.1% vs. 3.1%; P < 0.001) compared with CDAs, which was further corroborated in fixed-effects analysis. When stratified by length of follow-up, a significant difference was seen in ASDeg, ASDis, and reoperation rates of studies with follow-up of 12–48 months versus >48 months, with the exception of ASDeg rates in the CDA cohort. Conclusions: Our study shows CDA results in significantly lower ASDeg, ASDis, and reoperation rates. Although CDA may be a viable alternative to ACDF, further long-term studies are warranted to ensure consistency and establish longevity of our findings.