Unilateral Biportal Endoscopy for L5-S1 Extraforaminal Stenosis (Far Out Syndrome) - Technical Note with Literature Review.

Introduction: Extraforaminal stenosis in L5-S1, or far-out syndrome (FOS), is defined as L5 nerve compression by the transverse process (TP) of the L5 and the ala of the sacrum and disc bulging with/without osteophytes and/or the thickened lumbosacral and extraforaminal ligament. This study aims to describe the unilateral biportal endoscopic decompression technique of the extraforaminal stenosis at L5-S1 or far out syndrome and evaluate its clinical results with a literature review. Case Report: A 44-year-old male presented with severe right sharp shooting pain in the buttock, thigh, leg, foot, and/or toes with numbness in the foot and toes (Visual Analog Scale [VAS] 8/10) for six months with an Oswestry disability index (ODI) score of 70%. Her pain aggravated when bending forward and performing daily routine activities. He also complained of exaggeration of pain in daily regular activities. On physical examination, power in the right lower limbs was 5/5 as per the Medical Research Council (MRC) grading, and deep tendon reflexes were normal. Pre-operative X-ray and CT scan showed no instability or calcified disc osteophyte, and magnetic resonance imaging showed extraforaminal stenosis due to disc herniation at L5-S1 in Figure 1. We performed UBE-L5-S1extraforaminal discectomy surgery to resolve his symptoms. The operative time was 68 min; blood loss was 30 mL. After surgery, the patient was followed up at one week, six weeks, three months, six months, 12 months, and two years. The pain and tingling sensation in the legs improved at the 1-week follow-up, with a VAS score of 0/10 and an ODI score of 10% at the 2-year follow-up. Patient satisfaction was surveyed using Macnab's criteria at the final follow-up visit of 2 years and was found to be excellent. Post-operative imaging showed a good extraforaminal decompression at L5-S. Conclusion: Unilateral biportal endoscopy technique has brought a paradigm shift in the treatment of spinal pathologies and has served as another treatment option for the past two decades. The UBE decompression technique for extraforaminal stenosis at L5-S1 has the advantages of minimally invasive spine surgery; it is a safe and effective treatment option for treating extraforaminal stenosis at L5-S1.