Anterior Cervical Discectomy and Fusion Versus Cervical Disc Arthroplasty for Cervical Degenerative Disc Disease: Alarming Rates of Bias

Study Design Cross-Sectional. Objectives Whether cervical disc arthroplasty (CDA) or anterior cervical discectomy and fusion (ACDF) yields better outcomes in cervical degenerative disc disease remains unsettled, and clinicians turn to evidence syntheses for guidance. These syntheses, however, may contain spin, a reporting bias that presents an intervention as more effective or safer than the data support. This study sought to characterize how often spin appears in reviews comparing ACDF and CDA, which forms it takes, and whether methodological quality, journal impact factor, or citation rate predicts spin outcomes. Methods PubMed, Web of Science, and Embase were searched for systematic reviews and meta-analyses directly comparing ACDF and CDA. Each article was assessed for spin using the Yavchitz classification system and for methodological quality (AMSTAR-2). Logistic and Poisson regression assessed whether study AMSTAR-2 rating, journal impact factor, and yearly citations predicted spin outcomes. Results 77 articles were included. Spin was identified in 49 (63.6%); all spin-positive reviews favored CDA. The most frequent types were claiming benefit despite high risk of bias (39.0%), overemphasis on efficacy (26.0%), and selective safety reporting (15.6%). AMSTAR-2 ratings were poor: 83.1% were critically low, 15.6% low, and 1.3% high. Lower AMSTAR-2 rating independently predicted spin (OR 0.182, 95% CI 0.048–0.689, p = 0.012); impact factor and citations did not. Conclusions Spin is prevalent in reviews comparing CDA with ACDF and uniformly favors CDA. Greater methodological rigor and balanced reporting are needed for evidence syntheses to reliably inform clinical decisions.