Transforaminal full-endoscopic decompression under local anesthesia for foraminal stenosis due to stable L5 isthmic spondylolisthesis, a technical note and review:Pars crisscross decompression.

Foraminal stenosis is one of the types of lumbar spinal stenosis. The pathology can be treated minimally invasively by full-endoscopic spine surgery (FESS). The final challenge in transforaminal FESS is foraminal stenosis in patients with stable isthmic spondylolisthesis at L5. This article provides a step-by-step explanation of how to achieve complete decompression. A cannula of 8 mm in diameter is docked at the base of the superior articular process of the sacrum. The pars crisscross that consists of the superior articular process at S1, the floating lamina, the inferior articular process at L4, and the pars ragged edge is then clearly seen endoscopically. Visualization of the pars crisscross is key to successful decompression. Starting with the superior articular process at S1, followed by partial removal of the floating lamina. Next, the tip of the inferior articular process at L4 is removed. The pars ragged edge is then carefully shaved. Finally, decompression of the exiting nerve root at L5 is confirmed. This report provides the first step-by step description of full-endoscopic decompression of foraminal stenosis under local anesthesia in patients with stable L5 isthmic spondylolisthesis, which we have named "full-endoscopic pars crisscross decompression". J. Med. Invest. 71 : 191-196, August, 2024.