Eight RCTs (1,976 patients) were included in the review. Sample size ranged from 19 to 541 patients. All of the included trials were classified as of low methodological quality with a high risk of bias.
Trials with a two-year follow-up (six RCTs): Patients treated with disk replacement showed a significant increase in the overall success rate (OR 1.79, 95% CI: 1.37 to 2.33) compared with anterior cervical diskectomy and fusion, with no significant heterogeneity (four RCTs; 1,192 patients). Patients with a total disk replacement also showed a significant decrease in the overall re-operation rate (OR 0.36, 95% CI 0.21 to 0.61) with no significant heterogeneity (four trials; 1,328 patients), and a significant decrease in the re-operation rate for revision (OR 0.12, 95% CI 0.02 to 0.64) with no significant heterogeneity (three RCTs; 865 patients). There was a slight, but not significant, decrease in the neck disability index score (SMD -0.009, 95% CI -0.44 to 0.27) with significant heterogeneity (Ι²=73%; four RCTs; 720 patients). Patients showed a decrease in neck pain scores (SMD -0.48, 95% CI -0.91 to -0.05) with no significant heterogeneity (two RCTs; 87 patients). There was no significant differences in arm pain between the groups. Quality of life scores for individual trials were also reported.
Trials with four-year or five-year follow-up (two RCTs): These trials also showed that total disk replacement tended to be more effective than anterior cervical diskectomy and fusion for some outcomes (full details given in the paper).