Enhanced Diagnosis and Management of Far‐Out Syndrome Using 3D Visualization and Uni‐Portal Non‐Coaxial Spinal Endoscopic Surgery: A Case Report With Literature Review

Background Far‐out syndrome (FOS) is an uncommon cause of L5 radiculopathy that may be missed when extraforaminal compression lies beyond routine imaging planes. This report describes the added value of three‐dimensional (3D) CT/magnetic resonance neurography (MRN) fusion for diagnosing persistent symptoms after lumbar endoscopic surgery and planning revision decompression. Case Presentation A 55‐year‐old woman had persistent right L5 radiculopathy after unilateral biportal endoscopic discectomy (UBED). CT/MRI suggested L5‐S1 extraforaminal stenosis. Patient‐specific 3D CT/MRN fusion showed the exiting L5 root compressed by the L5 transverse process, sacral ala, posterior osteophyte, disc protrusion, and ligaments, redirecting revision planning to the extraforaminal zone. Uni‐portal non‐coaxial spinal endoscopic surgery (UNSES) achieved targeted bony, ligamentous, and disc decompression without vascular, neural, or dural injury. From pre‐revision values of VAS 7/10 for back pain and 7/10 for leg pain, ODI 54%, and JOA 5, scores improved at postoperative Day 1 to 3/10, 2/10, 22%, and 23, respectively. At 1, 3, and 6 months, back/leg VAS was 2/1, 1/0, and 1/0; ODI was 24%, 16%, and 8%; and JOA was 23, 25, and 27, respectively. Conclusions In this patient, 3D CT/MRN fusion complemented conventional imaging by integrating bone, disc, and nerve anatomy and directly informing revision decompression. UNSES was feasible, with improvement maintained through 6 months. As a single case, these findings support clinical feasibility and educational value rather than general efficacy or safety.