Transforaminal Full-Endoscopic Lumbar Foraminotomy Under Local Anesthesia for L5/S1 Adjacent Segment Foraminal Stenosis.

Foraminal stenosis in patients with L5/S1 adjacent segment disease (ASD) presents a significant clinical challenge, as conventional treatment often requires fusion extension surgery. This approach sacrifices spinal mobility and is associated with considerable surgical morbidity. This video article describes a motion-preserving surgical alternative, namely, transforaminal full-endoscopic foraminotomy performed under local anesthesia, detailing a step-by-step protocol to navigate the challenges of these revision cases. The technique utilizes a posterolateral corridor, avoiding prior surgical scarring. Key procedural steps include meticulous preoperative trajectory planning, foraminoplasty via resection of the superior articular process (SAP), and partial resection of the inferior articular process to fully expose the ligamentum flavum (LF). A specific "detach" technique is then demonstrated, involving undercutting the ventral rim of the S1 SAP to release the LF before its removal. Representative results demonstrate successful osseous decompression confirmed by postoperative computed tomography. The procedure resulted in immediate improvement in radicular pain and motor weakness, with the patient's visual analog scale score decreasing from 9/10 to 1/10 at the one-month follow-up. This minimally invasive technique provides effective neural decompression and facilitates rapid recovery, offering a valuable alternative to more extensive surgery for this challenging patient population.