33 patients with a symptomatic soft disc herniation were randomized to either receive a cervical spine disc prosthesis or anterior cervical discectomy and fusion (ACDF) as treatment for this condition. this study aimed to comparatively evaluate segmental motion following implantation. The results at the 6 month follow up period indicated that the use of both a disc prosthesis, as well as anterior cervical discectomy and fusion, decreased cervical spine segmental motion. A higher loss of motion, however, was seen in those who received the ACDF procedure.