1. Institute for Research in Operative Medicine (IFOM), Witten/Herdecke University, 51109 Cologne, Germany
2. Chair of Research Methodology and Statistics, Department of Psychology, Witten/Herdecke University, 58448 Witten, Germany
3. Department of Anaesthesiology and Operative Intensive Care, Cologne Merheim Medical Centre, 51109 Cologne, Germany
4. Institute for Emergency Medicine, University Hospital Schleswig-Holstein, 24118 Kiel, Germany
5. Department of Trauma Surgery, Cologne Merheim Medical Centre, 51109 Cologne, Germany