Fig. 2From: Cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) in symptomatic cervical degenerative disc diseases (CDDDs): an updated meta-analysis of prospective randomized controlled trials (RCTs)Assessment of risk of bias for the included studies is shown. + = low risk of bias; − = high risk of bias; ? = unclear risk of biasBack to article page