INTRODUCTION: Lumbar total disc replacement (TDR) vs. fusion trials have found TDR to yeild outcomes similar or superior to fusion. The question has arisen if results may be influenced by patients' enthusiasm for getting the new technology, creating what we have termed “euphoric bias”. The purpose of this study was to compare results of the same TDR when used as the investigational device vs. results when serving as a control.
METHODS: The same brand of TDR was implanted in three patient subgroups at a single center: prospective FDA randomized trial (patients randomized to Charite or fusion) as the investigational device (n=48; investigational group); the same protocol under continued access (not randomized; n=12); and as the control in the Kineflex‐L FDA trial (n=28; Control group; patients randomized to one of two TDRs). All patients were treated for single‐level disc degeneration at L4‐5 or L5‐1. There were no significant differences between groups based on age, gender, body mass index, or level operated.
RESULTS: There were no significant differences in Oswestry scores with respect to the TDR subgroups (Figure 1; ANOVA, p>0.05). All groups improved significantly by 6‐week follow‐up and remained improved through 24‐month follow‐up (p<0.01). There was no significant difference in the 24‐month re‐operation rate between groups (investigational 6.1%, continued access 0.0%, and control 3.6%; p>0.05).
DISCUSSION: There was no difference in results when comparing TDR as the “new” investigational device to which patients were randomized, patients knowing they would receive the same device as part of a continued access study, or when the same device served as the control, rather than the new investigational device. This study found that the good results reported for TDR are not likely to be related to a euphoric bias created by being randomized to receive the “newest” technology.