Oral Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

INTRODUCTION: One important factor associated with spinal surgery is restoration of spinal sagittal alignment. In the treatment of patients with painful disc degeneration, this is often achieved with the use of lordotic lumbar interbody fusion cages. Lumbar total disc replacement (TDR) implants also come in a variety of heights and endplate angles to address disc space collapse and spinal curvature. There is very little information available on the impact of TDR on sagittal alignment. The purpose of this study was to compare pre- to post-TDR sagittal alignment, disc heights, and disc space angulation based on full-body imaging.

METHODS: This retrospective study included 132 patients who had a full body EOS scan before TDR and at their first post-operative office visit. Data were collected by chart review which included general descriptors (sex, age, height, and weight) and surgery data. Radiographic measurements were completed on the SterEOS for both pelvic and postural parameters. In addition to the EOS measurements, L1-S1 segmental disc angles and disc heights were measured using PACS applied to the EOS images.

RESULTS: Of the total patients, 69.7% were male (n=92) with an average age and BMI of 41.4 years and 27.7 kg/m², respectively. There were 178 TDR devices implanted, with most operations at only 1-level (n=89), followed by 2-level operations (n=40), and 3-level operations (n=3). There were 3 sagittal alignment measurements with statistically significant changes after TDR surgery: sacral slope, sagittal pelvic tilt, and spino-sacral angle (Table 1). Both sacral slope and spino-sacral demonstrated an increase while sagittal pelvic tilt decreased. The mean disc heights increased significantly in the operated and non-operated groups (Figure 1a; though not a relevant change in non-operated levels). There was a statistically significant increase in the disc angulation of operated levels and a significant decrease in the non-operated levels (Figure 1b).

DISCUSSION: Lumbar TDR was associated with statistically increased sacral slope and spino-sacral angle, and a statistically significant decrease in sagittal pelvic tilt. Additionally, there was a demonstrably increased disc height and segmental angulation of the operated levels with a decrease in disc angulation of the non-operated levels. It may be speculated that these changes reduce adjacent segments compensation for the degeneration of the operated level. Long-term follow-up will allow us to determine if these early changes are maintained and their potential impact on clinical outcome.