1. Department of Trauma and Orthopaedic Surgery, Cologne-Merheim Medical Center (CMMC); University of Witten/Herdecke; Cologne Germany
2. Institute for Research in Operative Medicine (IFOM); University of Witten/Herdecke; Cologne Germany
3. Clinic of Surgery and Orthopaedics; Kantonales Spital Grabs; Grabs Switzerland
4. Clinic of Neurosurgery; Kantonsspital St. Gallen; St. Gallen Switzerland
5. Biometrics and Statistics; Institute for Research in Operative Medicine (IFOM); University of Witten/Herdecke; Cologne Germany
6. Department of Abdominal, Vascular, and Transplant Surgery; Cologne Merheim Medical Center (CMMC); University of Witten/Herdecke; Cologne Germany