Short-segment fusion versus isolated decompression in lumbar spinal canal stenosis patients with Cobb angles over 20 degrees

Background context: Lumbar 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.

Purpose: This 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 design: A retrospective analysis of a prospectively collected registry.

Patient sample: Patients 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 measures: Patient-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.

Methods: A 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.

Results: Before overlap weighting, the two surgery groups showed significant differences in age and diagnosis. No obvious sagittal malalignment was observed (PI minus LL: 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=.013; VAS back: fusion, 1.5±2.1 vs. decompression, 3.7±1.9, p<.001). Radiographic assessment showed that the fusion group achieved better PI minus LL compared to decompression group (15° vs. 10°, p=.008).

Conclusion: In 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.