Full Decompression of Spinal Stenosis in Stable Adult Isthmic Spondylolisthesis With a Combination of Full Endoscopic Spine Surgery and Unilateral Biportal Endoscopic Spine Surgery: A Case Report

<h3>Background</h3> Adult isthmic spondylolisthesis often remains stable in adulthood, but progressive neural compression can occur due to scar tissue, bony overgrowth, and disc degeneration. Conventional endoscopic techniques such as the interlaminar or transforaminal approaches may be limited by anatomical constraints in adult isthmic spondylolisthesis, making complete decompression difficult. <h3>Methods</h3> A 70-year-old man presented with bilateral leg pain and neurogenic claudication. Imaging revealed bilateral L4 to L5 lateral recess narrowing, L5 foraminal stenosis, and a bulging L5 to S1 disc compressing the extraforaminal nerve roots. A novel craniocaudal interlaminar approach via unilateral biportal endoscopic spine surgery was used to decompress the central and contralateral foraminal regions. The residual ipsilateral extraforaminal lesion was accessed through a separate full endoscopic transforaminal approach. Three incisions of 7 mm each were used. <h3>Results</h3> The patient experienced immediate and significant relief of radicular symptoms and improved function and was discharged the next day. At 18-month follow-up, he remained pain-free and without new-onset back pain or signs of instability. <h3>Conclusions</h3> This is the first reported case combining unilateral biportal endoscopic spine surgery and full endoscopic spine surgery. The approach enabled full decompression from central to extraforaminal zones with minimal invasiveness. This dual-endoscopic strategy may serve as a model for treating complex spine cases not amenable to single-approach techniques. <h3>Level of Evidence</h3> 4.