Effect of Degenerative Spondylolisthesis on the Clinical Outcome of Unilateral Biportal Endoscopy for Lumbar Spinal Stenosis: Study Protocol

Inclusion Criteria: * Age range: 50-80 years * Diagnosis of LSS affecting 1-2 vertebral levels * Predominant manifestation of neurogenic intermittent claudication, with ineffective conservative treatment for at least 3 months * Presence of lumbar DS of less than grade II and absence of spine instability * Willingness to participate in the study and complete follow-up assessments. Exclusion Criteria: * Diagnosis of isthmic lumbar spondylolisthesis or lumbar DS of grade ≥II * Evidence of instability at the affected vertebral level (intervertebral angle change \> 15° and/or vertebral translation ≥ 4.5 mm in standing flexion-extension radiographs of the lumbar spine) * History of prior surgery at the affected vertebral level * Presence of scoliosis with a Cobb angle \>20º * Presence of other conditions affecting the lumbar spine (infection, tumor, fracture, neurological diseases, and others) * Medical disorders that preclude surgical tolerance * Participation in other clinical research projects related to the treatment of lumbar spinal stenosis.