Study Design. Comparison of X-ray measurements in a randomized controlled trial between instrumented posterior fusion (N=72) and total disc replacement (TDR) (N=80) for chronic low back pain assumed to be discogenic. Results were compared to clinical outcome.
Objective. To see if surgical goals for respective treatments had been reached, if clinical outcome was related to this, and if differences in disc height and adjacent segment motion patterns between groups occurred.
Summary of Background Data. Fusion is considered the “gold standard” in surgical treatment of degenerated disc disease, though the resulting stiffness may induce degeneration in adjacent segments. TDR aims to restore and maintain mobility by replacing a painful disc. Little is known about the degree and quality of mobility in artificial discs in vivo, and whether maintained mobility reduces stress on adjacent segments.
Methods. Flexion-extension X-rays were analyzed pre- and two years postoperatively using Distortion Compensated Roentgen Analysis (DCRA) at treated and adjacent levels, mobility following fusion and TDR was estimated. Changes in disc height and changes in mobility patterns in adjacent segments were compared. The results were compared with clinical outcome regarding back pain.
Results. 78% of fused patients had no mobility whereas 89% of TDR-patients were mobile, but with less than normal mobility. The fulfilment of surgical goals was not correlated to clinical outcome. Fused segments were lower and TDR-segments were higher than normal. There were minor differences, there being more translation or flexion-extension at adjacent levels in the fusion group than in the TDR group.
Conclusions. This very accurate X-ray method (DCRA) indicates that surgical goals were reached in most patients. This however, was not correlated to outcome. Differences between the groups in postoperative disc height and motion patterns at adjacent segments may lead to differences in outcome in the long-term perspective, but this was not detectable after two years.