Ultrasound guidance for transforaminal percutaneous endoscopic lumbar discectomy may prevent radiation exposure: A case report

Figure 4 Cannulation process of the two endoscope outer sheaths. A: The endoscope outer sheaths were inserted through the guidance wire; B: Ultrasound (US) image of one sheath (white arrow indicates the track of the sheath; the tip of the sheath was hidden in the US shadow and could not be displayed); C: Position of the sheaths in the anteroposterior X-ray image; D: Position of the sheaths in the lateral X-ray image.