Cervical spine alignment, kinematic restoration, and clinical implications after disc arthroplasty: A systematic review and network meta-analysis

Study Design: Network meta-analysis of randomized controlled trials (RCTs) and comparative cohort studies. Objective: To compare different cervical disc prostheses based on sagittal alignment parameters, motion preservation, clinical results, and adverse events. Summary of Background Data: Despite the growing adoption of cervical disc replacement (CDR) as an alternative to ACDF, surgeons currently lack evidence-based guidance for selecting among different CDR devices. Methods: PubMed, Cochrane Library, and Google Scholar searches were conducted for all published eligible studies till December 31, 2024. Surface under the cumulative ranking curve (SUCRA) values were used to rank implant performance. Meta-regression was used to examine correlations between radiographic and clinical parameters. Results: Twenty-six studies (20 RCTs and 6 cohort studies) comprising 2892 CDR patients and 2638 ACDF patients with ACDF were analyzed. SUCRA analysis ranked M6-C as the top device with 66% overall performance across the alignment and clinical domains, followed by SECURE-C (58%) and Mobi-C (56%). ProDisc-C and Activ-C best maintain C2–7 lordosis. Prestige-LP best maintained the range of motion (MD 11.40°, 95% CI: 5.43–17.37). Clinical outcomes varied, with the best improvement in neck Oswestry index (NDI) for Simplify (MD: −9.40, 95% CI: −15.15 to −3.65). Meta-regression revealed significant correlations between C2 and 7 lordosis improvement and Japanese orthopedic association (JOA) scores ( t =8.446, P <0.001) and index level angle lordosis with reduced ASD ( t =5.601, P =0.030) and subsidence ( t =4.364, P =0.022). Conclusions: M6-C, prestige-LP, simplify, and ACDF showed a trend of better overall performance compared with other devices across parameters of sagittal alignment, preservation of motion, clinical outcomes, and adverse events, respectively. However, the recent M6-C reported complications, and the performance of SECURE-C and Mobi-C suggests that semi-constrained designs may provide a better balance, circumventing issues found in both unconstrained and constrained devices. These findings emphasize the importance of individualized device selection and long-term safety monitoring.