Patient-Reported and Radiographic Outcomes at Two Years Following Unilateral Biportal Endoscopic Fusion Extension for Adjacent Segment Disease: A Retrospective Cohort Study

Study DesignRetrospective cohort study.ObjectivesTo evaluate the mid-term clinical effectiveness, radiographic fusion rates, and safety profile of unilateral biportal endoscopic fusion-extension surgery (UBE-FES) in patients with symptomatic adjacent segment disease (ASD) after prior lumbar fusion.MethodsWe reviewed patients treated with UBE-FES between March 2020 and March 2023, each with ≥24 months of follow-up. Inclusion required new radicular or back pain from adjacent-level stenosis or Grade I-II spondylolisthesis. Clinical outcome measures were collected preoperatively and at 3, 6, 12, and 24 months. Operative time, blood loss, hospital stay, and complications were recorded. Fusion status was assessed on 12-month CT (Bridwell grades).ResultsMean operative time was 176 ± 22 min, blood loss was 185 ± 33 mL per level, and hospital stay was 6 ± 2 days. At 24 months, VAS-Back fell from 6.8 ± 0.5 to 0.1 ± 0.3 and VAS-Leg from 6.6 ± 0.6 to 0.1 ± 0.3 (both <i>P</i> < 0.001). ODI improved from 31.6 ± 5.0% to 3.5 ± 1.2% (<i>P</i> < 0.001). SF-36 PF increased from 16.1 ± 4.4 to 68.5 ± 18.2 and BP from 26.9 ± 6.4 to 72.3 ± 19.5 (<i>P</i> < 0.001). Fusion was achieved in 96.9%. Complications included one incidental durotomy (3.1%) and two asymptomatic cage subsidence events (6.3%); no infections or new neurologic deficits occurred.ConclusionsUBE-FES provides significant pain relief, functional improvement, and high fusion rates with minimal morbidity in ASD patients. These findings support UBE-FES as a viable alternative to open revision.