Does Spondylolisthesis Reduction Improve Long-term Outcomes?

Introduction: The impact of spondylolisthesis reduction on outcomes is an active research area, with newer techniques potentially enabling safer reductions. In patients undergoing primary, single-level lumbar decompression/fusion for grade I-II spondylolisthesis, we aimed to evaluate the effect of spondylolisthesis reduction on 1) reoperation rates, 2) patient-reported outcomes (PROMs), and 3) need for spinal injections.

Methods: This single-institution, retrospective cohort study included patients undergoing primary single-level lumbar decompression/fusion for spondylolisthesis from 2010-2021. Primary exposure was spondylolisthesis reduction (≥2 mm) and segmental lordosis improvement (≥5°). The primary outcome was long-term reoperation and secondary outcomes included 2-year PROMs. Descriptive and multivariable analyses were performed.

Results: In a cohort of 339 patients undergoing single-level lumbar decompression/fusion for spondylolisthesis, with a mean follow up of 6 years, 90% had grade I spondylolisthesis, and 65.5% received interbody fusion.
Spondylolisthesis reduction: A 2 mm reduction was seen in 161 (47.5%) patients. Complete reduction occurred in only 16 (4.7%) patients. Reoperation rates were similar between those with and without reduction (12.4% vs. 11.8%, p=0.860) and complete reduction or not (12.5% vs. 12.0%, p=0.599). Spondylolisthesis reduction was not significantly associated with the need for spinal injections (31.4% vs 25.8%, p = 0.615) or PROMs including MCID of ODI or NRS-back/leg pain (all p>0.05) at two years or at long-term follow-up.
Segmental lordosis: Mean postoperative segmental lordosis was 19.6±8.1º and 118 (34.8%) had improvement by at least 5°. No difference in the rate of reoperation (10.2% vs 13.1%, p=0.427), need for spinal injections (35% vs 26.1%, p=0.462) or PROMs (all p>0.05) was seen in patients with improved segmental lordosis or not.
Multivariable regression confirmed the lack of significant differences across these outcomes.

Conclusion : In patients undergoing elective, primary, single-level lumbar decompression/fusion for spondylolisthesis, half experienced a 2mm reduction, with only 5% achieving complete reduction. No significant difference was found in long-term reoperation, PROMs, and spinal injections based on spondylolisthesis reduction. These results underscore the complexity of treating spondylolisthesis and highlight the need for further research to optimize long-term outcomes.