Bilateral-Contralateral Endoscopic Decompression as a Fusion-Deferral Strategy in Upper Lumbar Stenosis: A Structural Rationale and Conditional Framework-A Technical Note with Cases Review.

Background/Objectives: Upper lumbar spinal stenosis presents unique challenges because vertically oriented facet joints and narrow laminae increase the risk of iatrogenic instability following decompression. Traditional decompression techniques may damage the facet joints, potentially resulting in further instability and degeneration. This study introduces a novel, facet-preserving bilateral-contralateral decompression strategy using unilateral biportal endoscopy (UBE) for upper lumbar stenosis, aiming to defer unnecessary spinal fusion. Methods: This retrospective series of three cases involved patients with upper lumbar stenosis characterized by vertically oriented facets (>60°) and narrow laminae, including cases of adjacent segment stenosis (ASS) and stenosis with grade 1 spondylolisthesis. Patients were selected using the authors' facet angle-based criteria (>60°) and laminar morphology to identify anatomically vulnerable segments. All patients exhibited vertical facet orientation and narrow laminae, without significant dynamic instability or severe foraminal compromise. Bilateral-contralateral decompression was performed using biportal endoscopy to preserve facet integrity and defer fusion where feasible. Results: This series demonstrated that bilateral-contralateral decompression provided effective neural decompression and symptom relief while preserving facet structures in the upper lumbar spine characterized by vertical facets and narrow laminae. No progression to instability or requirement for additional fusion was observed during the 6-month follow-up, even among patients with ASS and grade 1 spondylolisthesis. Conclusions: The authors propose that bilateral-contralateral decompression may serve as a facet-preserving and fusion-deferral strategy for upper lumbar stenosis with vertically oriented facets and narrow laminae. This approach is particularly applicable in cases such as ASS and spinal stenosis with grade 1 spondylolisthesis, where preserving structural reserve is critical. These preliminary findings highlight the need for prospective validation through carefully designed observational studies and larger case series.