Radiographic and clinical outcomes at 12 months following full endoscopic interlaminar decompression for grade 1 degenerative lumbar spondylolisthesis.

Lumbar spinal stenosis (LSS) frequently coexists with degenerative spondylolisthesis (DS) in the elderly population, and the standard treatment commonly involves decompression with fusion. However, fusion procedures are associated with increased morbidity and may not always be necessary, particularly in Grade I DS. Full-endoscopic unilateral laminotomy for bilateral decompression (LE-ULBD) has gained attention as a motion-preserving alternative, yet its impact on postoperative stability remains insufficiently studied. Primary objective was to evaluate 12-month improvements in patient-reported outcomes (leg-pain VAS, ODI) after LE-ULBD; radiographic stability was assessed as a key secondary endpoint. This retrospective cohort study included 32 patients with Meyerding stable Grade I DS and symptomatic LSS who underwent single-level lumbar LE-ULBD between January 2023 and October 2024. Pre- and 12-month postoperative radiographs were analyzed for segmental instability, defined as sagittal translation > 4 mm or angular motion > 10°. Clinical outcomes were assessed using Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and Macnab's criteria. Subgroup analysis was performed based on slip progression. Mean vertebral slip percentage showed no significant change postoperatively (13.4% ± 3.1 vs. 13.8% ± 3.4; p = 0.27). Only one patient (3.1%) developed new radiographic instability. VAS improved from 7.1 ± 1.2 to 1.4 ± 0.8 and ODI from 64.3% ± 9.1 to 18.5% ± 4.7 (p < 0.001 for both). According to Macnab's criteria, 90.6% of patients reported Excellent or Good outcomes. Slip progression was observed in 9 patients (28.1%), but this was not associated with inferior clinical results. Complications occurred in 2/32 (6.3%) one incidental durotomy and one epidural hematoma with reoperation in 1/32 (3.1%); new radiographic instability in 1/32 (3.1%). LE-ULBD appears to be a safe and effective treatment option for selected patients with Grade I DS and LSS, achieving significant symptomatic relief while preserving segmental stability in the majority of cases. These findings support its consideration as an alternative to fusion in carefully selected individuals. LE-ULBD short-term (12-month) radiographic stability and clinically meaningful improvement in patients with stable grade-I degenerative spondylolisthesis; longer-term follow-up is required to determine durability and late instability risk.