1. Department of Orthopedics and Trauma Surgery, University Hospital, Düsseldorf, Germany
2. Department of Orthopedic and Trauma Surgery, Medical Faculty, University of Cologne, Cologne, Germany
3. Center for Spine Surgery, St Remigius Hospital Leverkusen, Leverkusen, Germany
4. Spine Department, Center for Musculoskeletal Surgery, Charité University Medicine Berlin
5. Department of Orthopaedics, Trauma Surgery and Plastic Surgery, University Hospital Leipzig
6. Department of Trauma and Reconstructive Surgery, Halle, Germany
7. Department of Trauma Hand and Reconstructive Surgery, University Hospital Jena, Jena Germany
8. Center for Spinal and Scoliosis Surgery, Waldkrankenhaus Erlangen, Germany
9. Department of Orthopedics and Traumatology, Paracelsus Private Medical University Nuremberg, Nuremberg, Germany