How Age and BMI Are Associated with Adjacent Segment Disease in Standalone Lateral Lumbar Interbody Fusion

Introduction: The pathogenesis of adjacent segment disease (ASD) following lumbar fusion has been described in the literature as multifactorial in nature, with some associations made with patient-specific factors such as body mass index (BMI) and age. However, few studies have examined the development of ASD in the context of advanced age and elevated BMI with standalone lateral lumbar interbody fusion (LLIF) procedures. Examining the role of patient-specific and potentially modifiable factors is important for improving outcomes associated with minimally invasive techniques, such as the LLIF, that are becoming more frequently used in the treatment of degenerative lumbar disease.

Methods: We performed a retrospective chart review on all patients receiving standalone LLIF from 2014-2022. 140 patients met inclusion criteria. The initial time of diagnosis of RASD adjacent to the fused levels was recorded in months and sorted into groups of < 6 months, 6-12 months, and >12 months.

Results: The mean age of the study cohort (n=14) was 63.5 (SD = 10.1) and the mean BMI was 29.9 (SD = 5.41). In patients who developed ASD following surgery (30.5%), there was a significant moderate negative correlation with age and the time until the development of ASD (rp = -.315, p < 0.05). Chances of developing ASD were higher in those over 65, but not statistically significant (OR = 1.74, 0.84 3.61 95% CI). There was no significant correlation between BMI and the incidence or time until development of ASD, and no correlation was found between the incidence of ASD and age.

Conclusion : In patients receiving standalone LLIF procedures, advanced age was associated with more rapid development of radiographic ASD. The incidence of ASD was not significantly associated with BMI or age, suggesting that further evaluation must consider length of follow-up and previous history of degenerative lumbar disease within this population.