Adjacent Segment Disease Following Two-Level Axial Lumbar Interbody Fusion: A Long-Term Follow-Up Study

Introduction: Adjacent-segment disease (ASD) is a well-recognized potential complication following posterior lumbar spine arthrodesis, yet the long-term incidence and prevalence of ASD following two-level axial lumbar interbody fusion (AxiaLIF) are not well defined. This study aims to estimate the incidence and prevalence of ASD following two-level AxiaLIF, building on the five-year outcomes from our prior research. To our knowledge, this is the largest reported number of cases that underwent two-level AxiaLIF in the United States.

Methods: We retrospectively analyzed 149 patients who underwent two-level AxiaLIF with concurrent percutaneous pedicle screw fixation at our institution. ASD and index-level reoperations were evaluated in each patient. ASD was defined as radiographic and clinically significant disease at a level adjacent to a previous fusion requiring surgical intervention.

Results: Mean follow-up was 13.6 years. Preliminary chart reviews revealed that 24 (16.1%) of the 149 patients developed ASD and 28 (18.8%) developed or had residual index level disease requiring operations. Kaplan-Meier analysis showed a disease-free ASD survival rate of 87.9% ± 2.7% at 5 years, 84.6% ± 3.0% at 10 years, and 83.7% ± 3.0% at 15 years after the two-level AxiaLIF. Additionally, Kaplan-Meier showed a disease-free index-level reoperation survival rate of 81.2% ± 3.2% at 5, 10, and 15 years. An adjacent segment decompression prior to AxiaLIF is associated with 4.1 times the relative risk of developing ASD (95% confidence interval, 1.89-8.67; p < 0.001).

Conclusion : Following two-level AxiaLIF, the rate of symptomatic ASD warranting surgical intervention was found to be 12.1% at 5 years, 15.4% at 10 years, and 16.3% at 15 years. Since the five-year follow up study, four additional patients were found to have adjacent-segment disease. No index-level reoperations occurred beyond the first 5 years after the initial two-level AxiaLIF. Most adjacent segment and index-level operations occur within 5 years of the initial procedure.