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Various total disc replacement (TDR) designs have been compared to anterior cervical discectomy and fusion (ACDF) with favorable short and long-term outcomes in FDA-approved investigational device exemption (IDE) trials. The unique design of M6-C, with a compressible viscoelastic nuclear core and an annular structure, has previously demonstrated favorable clinical outcomes through 24 months. To evaluate the long-term safety and effectiveness of the M6-C compressible artificial cervical disc and compare to ACDF at 5 years. Prospective, multicenter, concurrently and historically controlled, FDA-approved IDE clinical trial. Subjects with one-level symptomatic degenerative cervical radiculopathy were enrolled and received M6-C (n=160) or ACDF (n=189) treatment as part of the IDE study. Safety outcomes were evaluated at 5 years for all subjects. The primary effectiveness endpoint was available at 5 years for 113 M6-C subjects and 106 ACDF controls. The primary endpoint of this analysis was composite clinical success (CCS) at 60 months. Secondary endpoints were function and pain (neck disability index, VAS), physical quality of life (SF-36, SF-12), safety, neurologic, and radiographic assessments. Propensity score subclassification was used to control for selection bias and match baseline covariates of the control group to the M6-C subjects. Sixty-month CCS rates were estimated for each treatment group using a generalized linear model controlling for propensity score. At 5 years postoperatively, the M6-C treatment resulted in 82.3% CCS while the ACDF group showed 67.0% CCS (superiority p=.013). Secondary endpoints indicated that significantly more M6-C subjects achieved VAS neck and arm pain improvements and showed maintained or improved physical functioning on quality-of-life measures compared to baseline assessments. The M6-C group-maintained flexion-extension motion, with significantly greater increases from baseline disc height and disc angle than observed in the control group. The rates of M6-C subsequent surgical interventions (SSI; 3.1%) and definitely device- or procedure-related serious adverse events (SAE failure; 3.1%) were similar to ACDF rates (SSI=5.3%, SAE failure=4.8%; p>.05 for both). Subjects treated with the M6-C artificial disc demonstrated superior 5-year achievement of clinical success when compared to ACDF controls. In addition, significantly more subjects in the M6-C group showed improved pain and physical functioning scores than observed in ACDF subjects, with no difference in reoperation rates or safety outcomes. [ABSTRACT FROM AUTHOR]

Study Design. Prospective randomized controlled trial. Objective. Compare range of motion (ROM) and adjacent segment degeneration (ASD) following cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) at 20-year follow-up. Summary of Background Data. Anterior cervical discectomy and fusion is the standard of treatment for single-level cervical disc degeneration causing radiculopathy. CDA is claimed to reduce shear strain, and adjacent-level ROM changes are hypothesized to hasten ASD with ACDF. Materials and Methods. This study collected data on 47 patients randomized to ACDF or CDA. Lateral cervical spine radiographs were evaluated preoperatively, postoperatively, and at 20 years for alignment, ROM, ASD, and heterotopic ossification. Results. Eighty-two percent (18/22) of CDA patients and 84% (21/25) of ACDF patients followed up at 20 years. At 20 years, total cervical (C2--C7) ROM was statistically different between the CDA and fusion groups (47.8° vs. 33.4°, P=0.005). Total cervical ROM was not significantly different between preoperative and 20-year periods following CDA (45.6° vs. 47.4°, P=0.772) or ACDF (40.6° vs.33.0°, P=0.192). Differences in postoperative and 20-year index-level ROM following CDA were not significant (10.1° vs. 10.2°, P=0.952). Final ASD grading was statistically lower following CDA versus ACDF at both adjacent levels (P<0.005). Twenty-year adjacent-level ossification development was increased following ACDF versus CDA (P<0.001). Polyethylene mean thickness decreased from 9.4 mm immediately postoperatively to 9.1 mm at 20-year follow up (P=0.013). Differences in adjacent-level ROM from preoperative to 20-year follow-up in both the ACDF and CDA groups did not meet statistical significance (P>0.05). Conclusions. Cervical disc arthroplasty maintains index-level and total cervical ROM with very long-term follow-up. Total cervical ROM was higher at 20 years in CDA relative to ACDF. CDA results in lower rates of ASD and adjacent-level ossification development than ACDF. [ABSTRACT FROM AUTHOR]