1. Department of Neurosurgery, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany
2. University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
3. Facultad de Medicina, Universidad de Sevilla, 41004 Sevilla, Spain
4. Department of Traumatology and Reconstructive Surgery, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117 Berlin, Germany
5. Faculty of Medicine, Ludwig-Maximilians-University, 80539 Munich, Germany
6. The GKT School of Medical Education, King’s College London, London WC2R 2LS, UK
7. Department of Orthopaedics and Neurosurgery, Schulthess Klinik, 8008 Zurich, Switzerland