1. Department of Minimally Invasive Spine Surgery, Orthopaedic Clinic, Faculty of Radiology and Microtherapy, University of Witten/Herdecke, St. Anna Hospital, Herne, Germany.
2. Department of Minimally Invasive Spine Surgery, Orthopaedic Clinic, Faculty of Radiology and Microtherapy, University of Witten/Herdecke, St. Anna Hospital, Herne, Germany.