Laminectomy alone vs laminectomy with posterior fusion in lumbar spinal stenosis: The role of instability

Lumbar spinal stenosis (LSS) is a common degenerative spinal disorder in older adults and a leading indication for surgery. Decompression via laminectomy remains the gold standard when conservative measures fail, but the addition of posterior fusion in cases without clear instability remains controversial. Anatomical and biomechanical considerations lie at the center of this debate. Central canal stenosis, lateral recess narrowing, and degenerative spondylolisthesis represent the main contributors to LSS, but they also raise the question of whether they signal true instability. Definitions of instability vary considerably across studies and guidelines, and thresholds for diagnosis remain inconsistent. While fusion is appropriate in the presence of instability, the lack of standardized criteria causes an uncertainty that may influence surgeons to fuse in cases without having definitive radiographic criteria for instability. The aim of this review is to compare laminectomy alone with laminectomy plus posterior fusion in the surgical management of LSS. Emphasis is given on anatomical and biomechanical considerations, instability definitions, clinical outcomes, and guideline recommendations. High-quality multicenter randomized trials are needed to develop universally accepted instability definitions, guide management of borderline cases, and optimize patient outcomes.