231 patients with symptomatic lumbar degenerative disc disease were randomized to undergo total disc replacement (TDR) with either a mobile core disc (MCD) or constrained core disc (CCD) implant system. The purpose of this posthoc analysis was to determine if either implant was associated with significantly improved postoperative range of motion, radiographic success, and clinical measures after two years. Results revealed that patients treated with MCD implants had significantly improved outcomes on all measures of interest and that patients who demonstrated >/= 6 degrees of improvement/maintenance in segmental ROM were more likely to additionally show significant improvements in pain severity and ODI scores.