Radiographic Changes in Spinopelvic Alignment Following Single-level Lumbar Total Disc Replacement

Introduction: Lumbar total disc replacement (LTDR) has emerged as an alternative to fusion for patients with degenerative disc disease (DDD) who do not respond to conservative treatment. There is limited literature on how LTDR impacts sagittal alignment parameters. Lumbar alignment plays a crucial role in spinal biomechanics and patient outcomes, making it essential to assess changes in these parameters following TDR. This study aims to assess the effect of LTDR on alignment by comparing pre- and post-operative spinopelvic parameters in single-level LTDR on patients.

Methods: A retrospective review was conducted at a quaternary spine center from 2013 to 2024. We identified 239 patients who underwent LTDR, excluding those with concomitant fusion, multi-level TDR, or incomplete preoperative imaging. 37 patients met inclusion criteria. Radiographic measurements included pelvic incidence, pelvic tilt, sacral slope, L4-S1 lumbar lordosis, total lumbar lordosis, and L1-pelvic angle (L1PA). Paired t-tests or Wilcoxon-signed rank tests were used depending on data normality (Shapiro-Wilk test).

Results: Of the 37 patients, 23 received TDR at the L5-S1 level, and 14 at the L4-L5 level. L1PA decreased significantly (p=0.005) following TDR. Conversely, there was a significant increase in distal lumbar lordosis (L4-S1) (p=0.0007). No significant changes were noted in total lumbar lordosis, pelvic tilt, sacral slope, or pelvic incidence.

Conclusion : This study demonstrated significant postoperative changes in key sagittal alignment parameters following single-level LTDR. The reduction of L1PA suggests an alteration in global spinal alignment, while the increase in distal lumbar lordosis may reflect restoration of optimal lumbar curvature. These findings highlight the impact of LTDR on spinopelvic alignment, which may influence patient long-term function. Further research is warranted to evaluate the clinical significance of these changes and their effects on adjacent segment disease, global alignment, and quality of life.