The purpose of this investigation is to establish the safety and effectiveness of the LDR Spine Mobi-C® Cervical Disc Prosthesis which is an anterior cervical interbody mechanical device. The primary objective of the study is to evaluate the overall success rate of the investigational device as compared to the control in the treatment of patients with symptomatic DDD with radiculopathy or myeloradiculopathy at one or two adjacent levels. Patients should be without prior cervical fusion between C3 and C7 and unresponsive to non-operative conservative treatment for six weeks after symptom onset or have the presence of progressive symptoms or signs of nerve/spinal cord compression despite continued non-operative conservative treatment.