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

Study Design Retrospective cohort study. Objectives To 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. Methods We 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). Results Mean 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 P < 0.001). ODI improved from 31.6 ± 5.0% to 3.5 ± 1.2% ( P < 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 ( P < 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. Conclusions UBE-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.