Twenty-Year Radiographic Outcomes Following Single-Level Cervical Disc Arthroplasty

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 degrees vs. 33.4 degrees, P=0.005). Total cervical ROM was not significantly different between preoperative and 20-year periods following CDA (45.6 degrees vs. 47.4 degrees, P=0.772) or ACDF (40.6 degrees vs. 33.0 degrees, P=0.192). Differences in postoperative and 20-year index-level ROM following CDA were not significant (10.1 degrees vs. 10.2 degrees, 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.