“…In a recent international spine registry study [313], the results of cervical disc replacement were in accordance with those in the published RCTs. Furthermore, in a Swiss registry study with five-year follow-up after lumbar TDR [197], the main results are similar to those in RCTs with a follow-up time of at least five years (Appendix, Table 1). Our results are in line with two small single centre Norwegian observational studies [314 315], while, in the Norwegian Spine Registry (2007-2013), the one-year mean improvement following TDR was 26.0 ODI points as compared to 22.5 ODI points after one year in the Norwegian TDR Study [316].…”