Background ContextLumbar decompression and short-segment lumbar fusion are standard procedures for short-segment lumbar canal stenosis, even in patients with moderate Cobb angles. Adult degenerative scoliosis is diagnosed at a threshold of 10 degrees, and patients with coronal Cobb angles over 30 degrees are recommended for long fusion due to global spinal deformity. However, there is a lack of research on clinical outcomes in patients with moderate coronal deformity, such as Cobb angles between 20 and 30 degrees. PurposeThis study aims to investigate the radiographic and clinical outcome differences between isolated decompression and short-segment interbody fusion for lumbar spinal canal stenosis in patients with moderate coronal deformity. Study DesignA retrospective analysis of a prospectively collected registry Patient SamplePatients with Cobb angle exceeding 20 degrees who underwent 1- or 2- levels of lumbar surgery for lumbar canal stenosis. Patients diagnosed as spinal deformity were excluded. Outcome MeasuresPatient-reported outcomes included Oswestry Disability Index (ODI), VAS back, VAS leg, Short Form 12 Physical Component Score (SF-12 PCS) and Mental Component Score (SF-12 MCS), and Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF) at preoperative, 12-week postoperative, and 1-year postoperative timepoints. Preoperative and postoperative spinopelvic alignment was assessed using Cobb angle, pelvic tilt, sacral slope, pelvic incidence, lumbar lordosis and PI minus LL. MethodsA propensity score-matched analysis with the overlap weighting was utilized to investigate patient-reported outcomes at 12-week and 1-year postoperatively between the surgery groups. Spinopelvic alignments were compared between preoperative and 1-year postoperative timepoint using a linear mixed-effect model. ResultsBefore overlap weighting, the two surgery groups showed significant differences in age and diagnosis. No obvious sagittal malalignment was observed (decompression, 7.4° vs. fusion, 11.5°). After propensity score weighting, the fusion groups exhibited significantly better ODI and VAS back at the 1-year timepoint (ODI: fusion, 16.6 vs. decompression, 28.1, P=0.013; VAS back: fusion, 1.5 ± 2.1 vs. decompression, 3.7 ± 1.9, P<0.001). Radiographic assessment showed that the fusion group achieved better PI minus LL compared to decompression group (15° vs. 10°, P=0.008) ConclusionIn patients with degenerative scoliosis and a Cobb angle greater than 20 degrees, short-segment lumbar fusion surgery may result in enhanced improvement for short-segment lumbar pathology compared to isolated decompression.