“Outside-in” Technique, Clinical Results, and Indications with Transforaminal Lumbar Endoscopic Surgery: a Retrospective Study on 220 Patients on Applied Radiographic Classification of Foraminal Spinal Stenosis

Preoperative MRI scans of a 64 year old female: a) panel on the left shows axial MRI cuts from L3 to L5, b-d) panel shows sagittal MRI cuts through the entry (shaded orange), middle (shaded turquoise), and exit zone (shaded green) of the lumbar neuroforamina, e) axial MRI cut through the L3-4 disc space showing the stenotic lesion in the exit zone at that level, f-g) sagittal MRI cuts through the exit zone at L3-4, and the L4-5 level. The neuroforaminal height (orange shade area) is less than 3 mm and hence consistent with spinal stenosis. At L4-5, the neuroforaminal height is 5 mm (orange shade area).