Sagittal alignment and segmental range of motion after total disc replacement of the lumbar spine

Aim: To evaluate changes in static and dynamic values, X-rays of patients who underwent total disc replacement for degenerative disc disease were analyzed. Method: An analysis of pre- and postoperative lateral X-rays in 22 patients with 24 total disc replacements (Prodics(R), Spine Solutions) was performed. The total lumbar lordosis, the segmental lordosis angle, the disc height and the range of motion in the operated level were measured. Results: Postoperatively a significant increase was observed for the following parameters: the anterior (pre: 9.0 +/- 3.4 mm; post: 16.7 +/- 2.4 mm; p < 0.001) and posterior (pre: 4.4 +/- 1.3 mm; post: 8.8 +/- 1.3 mm; p < 0.001) disc height and the segmental lordosis angle (pre: 20degrees +/- 7.2degrees; post: 27.7degrees +/- 7.4degrees; p < 0.001). Statistically no significant changes could be observed postoperatively for the total lumbar lordosis (pre: 56.2 degrees +/- 10.7 degrees; post: 58.6 degrees +/- 9.3 degrees; p=0.196) and the range of motion (pre: 5.0 degrees +/- 4.0 degrees; post: 5.9 degrees +/- 3.5 degrees; p = 0.293). Conclusion: Total disc replacement for degenerative disc disease of the lumbar spine with the current concept does not alter the range of motion but significantly increases the disc height. The significant increase in segmental lordosis without a change in the total lumbar lordosis accounts for a change in lordosis in adjacent segments.