The Relationship Between Postoperative Pelvic Incidence-Lumbar Lordosis Mismatch and Adjacent Segment Disease After Lateral Lumbar Interbody Fusion

Introduction: Adjacent Segment Disease (ASD) is one of the most significant long-term complications in lateral lumbar interbody fusion (LLIF). An elevated pelvic incidence-lumbar lordosis (PI-LL) mismatch has been reported in the literature to be related to the development of symptomatic or radiologic ASD. Establishing a statistically significant cutoff of PI-LL mismatch for ASD development after LLIF procedures could be an asset for surgical planning and anticipation of revision surgeries and patient outcomes.

Methods: Retrospective review of patients (n=78) who underwent standalone LLIF between 2014 and 2022 at a single institution was performed. Patients were excluded if they had less than 12 months of follow-up. Average follow-up time was 40 ± 25 months. Correlational analyses were performed. PI-LL mismatch was defined as >± 9 degrees. ASD was diagnosed radiographically (RASD).

Results: PI-LL mismatch was observed for 15 of the 23 patients diagnosed with RASD and 28 of the 55 without RASD. Although not statically significant, the group with PI-LL mismatch had an increased likelihood of developing RASD with an odds ratio of 1.808 (95% CI 0.660, 4.953). Pearson correlational analysis found little association and no significance in PI-LL angle and RASD development. Spearman correlational analysis of PI-LL angle and ASD also found a positive and mild association with time until diagnosis (0.325, p=0.131), yet still insignificant correlation.

Conclusion : Although no statically significant impact was established, the data hints that PI-LL mismatch of greater than ± 9 degrees may yield more patients with a future ASD diagnosis following standalone LLIF. With the large rate of ASD following LLIF, further investigation is warranted to add significance and establish risk factors a surgeon can utilize to improve long-term outcomes.