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A stereotactic system for needle entry for percutaneous endoscopic lumbar discectomy. (A) (Left) A computer-aided design was created with a scale for mimicking a stereotactic system. (Middle) A stereotactic system was designed without a scale. A 15 cm-long transparent ruler (x axis: coronal plane) attaching a wire below its bottom with a 90° protractor movable from 5 to 15 cm (angle to coronal plane) has a perpendicular movable wing which has also a wire (angle within sagittal plane). (Right) A case for the body, 2 K-wires, and protractor allowed the system to be easily carried and sterilized. The stereotactic system was made of acryl, wire, and screws. A tiny roller was applied on the middle and both ends to adjust the insertion angles of the needle. (B) The stereotactic system was applied to patients that underwent a single-level percutaneous endoscopic lumbar discectomy at L4-L5. (Left) The system was placed on the patient to confirm the midline of the spine and the intervertebral space from the anteroposterior view (Middle) and the intervertebral space from the lateral view (Right). A protractor was subsequently placed on the anticipated skin entry point, normally from 8 to 12 cm, according to preoperative magnetic resonance image.