ACDF reoperation and pseudoarthrosis rates are elevated in CDA trials compared to observational studies: systematic review and meta-analysis.

PURPOSE: To compare anterior cervical discectomy and fusion (ACDF) pseudoarthrosis and reoperation rates derived from randomized controlled trials (RCTs) comparing ACDF to cervical disc arthroplasty (CDA) versus other non-CDA studies. METHODS: This meta-analysis followed PRISMA guidelines. PubMed, Embase, Web of Science, Scopus, and Cochrane databases were reviewed for studies reporting reoperation and/or symptomatic pseudoarthrosis following ACDF. 61 studies involving 5,798 ACDFs were included. Analyses were stratified by Early (< 3 years), Mid (3-7 years), and Long (> 7 years) follow-up. Combined rates of reoperation and pseudarthrosis with 95% confidence intervals were obtained from random effects models. RESULTS: Ten CDA RCTs, sixteen observational, and two other RCTs not comparing against CDA were included at early-term follow-up. Reoperation following ACDF in early CDA RCTs versus observational and non-CDA RCTs was 7% [5-9] vs. 4% [3-6], p = 0.051. Symptomatic pseudoarthrosis in early CDA RCTs versus observational and non-CDA RCTs was 4% [3-7] vs. 3% [2-4], p = 0.083. Thirteen CDA RCTs, ten observational studies, and one other RCT were included at mid-term follow-up. Reoperation following ACDF was 4-fold higher in mid-term CDA RCTs versus observational studies and non-CDA RCTs (12% [10-16] vs. 3% [1-6], p < 0.001). Symptomatic pseudoarthrosis was 3-fold higher (6% [5-8] vs. 2% [2-4], p = 0.001). Eight CDA RCTs and one observational study were included at long-term follow-up. Overall reoperation did not differ. There were not enough studies of long-term pseudoarthrosis for comparison. CONCLUSIONS: The rates of reoperation and symptomatic pseudoarthrosis after ACDF were higher in CDA RCTs than observational studies at mid-term follow-up. This phenomenon could be driven by multiple sources of bias, including sampling, publication, or patient satisfaction bias.