The Clinical Relevance of the Cervical Disc Prosthesis: Combining Clinical Results of Two RCTs.

STUDY DESIGN Retrospective analysis was performed on data from two hundred fifty-one patients that were included in two randomized, double-blinded clinical trials comparing clinical results of ACDA to ACDF, and ACD, for single-level disc herniation. OBJECTIVE This study aimed to investigate whether the Anterior Cervical Discectomy and Arthroplasty (ACDA) procedure offers superior clinical results two years after surgery, to either Anterior Cervical Discectomy and Fusion (ACDF) or Anterior Cervical Discectomy without instrumentation (ACD), in the entire group of patients or in a particular subgroup of patients. SUMMARY OF BACKGROUND DATA The cervical disc prosthesis was introduced to provide superior clinical outcomes after anterior cervical discectomy (ACD). METHODS Neck Disability Index, and subscales of the SF36 and McGill pain score were collected at baseline, one year and two years after surgery. Re-operations and complications were also evaluated. A preliminary subgroup analysis was performed for age, disc height, BMI, smoking and gender. RESULTS The NDI decreased comparably in all treatment arms to circa 50% of the baseline value and marginal mean NDI differences varied from 0.4 to 1.1 on a 100 point NDI scale, with confidence intervals never exceeding the 20-point Minimal Clinical Important Difference (MCID). Secondary outcome parameters showed comparable results. Preliminary subgroup analysis could not demonstrate clinically relevant differences in NDI between treatments after two years. CONCLUSION After combining data from two RCTs it can be concluded that there is no clinical benefit for ACDA, when compared to ACDF or ACD two years after surgery. Preliminary subgroup analysis indicated outcomes were similar between treatment groups, and that no subgroup could be appointed that benefited more from either ACD, ACDF or ACDA.Level of Evidence: 1.