Background:

Adjacent segment disease (ASD) is a common problem after lumbar spinal fusions. Ways to reduce the rates of ASD are highly sought after to reduce the need for reoperation.

Objective:

To find predisposing factors of ASD after lumbar interbody fusions, especially in mismatch of pelvic incidence and lumbar lordosis (PI-LL).

Methods:

We conducted a retrospective cohort study of all patients undergoing lumbar interbody fusions of less than 4 levels from June 2015 to July 2020 with at least 1 year of follow-up and in those who had obtained postoperative standing X-rays.

Results:

We found 243 patients who fit inclusion and exclusion criteria. Fourteen patients (5.8%) developed ASD, at a median of 24 months. Postoperative lumbar lordosis was significantly higher in the non-ASD cohort (median 46.4° ± 1.4° vs 36.9° ± 3.6°, P < .001), pelvic tilt was significantly lower in the non-ASD cohort (16.0° ± 0.66° vs 20.3° ± 2.4°, P = .002), PI-LL mismatch was significantly lower in the non-ASD cohort (5.28° ± 1.0° vs 17.1° ± 2.0°, P < .001), and age-appropriate PI-LL mismatch was less common in the non-ASD cohort (34 patients [14.8%] vs 13 [92.9%] of patients with high mismatch, P < .001). Using multivariate analysis, greater PI-LL mismatch was predictive of ASD (95% odds ratio CI = 1.393-2.458, P < .001) and age-appropriate PI-LL mismatch was predictive of ASD (95% odds ratio CI = 10.8-970.4, P < .001).

Conclusion:

Higher PI-LL mismatch, both age-independent and when adjusted for age, after lumbar interbody fusion was predictive for developing ASD. In lumbar degenerative disease, correction of spinopelvic parameters should be a main goal of surgical correction.